HEAT AND CORROSION RESISTANT CASTINGS: …/Media/Files/TechnicalLiterature/Heat... · HEAT AND CORROSION RESISTANT CASTINGS: THEIR ENGINEERING PROPERTIES ... Steel Mill Equipment

HEAT AND CORROSION RESISTANT CASTINGS:

THEIR ENGINEERING PROPERTIES

AND APPLICATIONS

Publication No 266

NiDl Distributed by the Nickel Development Institute, courtesy of Inco Limited

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Part I. Heat-Resistant Alloy Castings ........................................................... 4-26

Introduction ....................................................................................................... 4

Typical Casting Compositions of Heat-Resistant Alloy Castings, Table I ...... 4 Effect of Constituents ........................................................................................ 5 Groups of Heat-Resistant Alloy Castings ...................................................... 6-8

Chromium-Iron Alloys (HA, HC, HD)

Chromium-Nickel-Iron Alloys (HE, HF, HH, HI, HK, IN-519, HL)

Nickel-Chromium-Iron Alloys (HN, HP, HT, HU, HW, HX)

Chromium-Nickel Alloys (50Cr-50Ni, IN-657)

Selecting the Proper Alloy ................................................................................. 8 Heat-Resistant Alloy Casting Design ................................................................ 9 High-Temperature Mechanical Properties ................................................... 9-15 High-Temperature Corrosion Resistance .................................................. 14,16 Room Temperature Properties ....................................................................... 16 Industrial Applications of Heat-Resistant Alloy Castings

Aeronautical ................................................................................................. 17

Cement ........................................................................................................ 17

Glass & Enameling ................................................................................. 17-18

Heat Treating .......................................................................................... 18-21

Petroleum, Petrochemical Refining &Chemical ...................................... 22-24

Power Plants ............................................................................................... 25

Steel Mill Equipment .................................................................................... 26

Smelting & Refining Equipment ................................................................... 26

Contents Pages

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Part II. Corrosion-Resistant Alloy Castings .......................................................... 27-47

Introduction ............................................................................................................... 27 Typical Casting Compositions of Corrosion-Resistant Alloy Castings, Table V .... 27 Room Temperature Properties ................................................................................. 28 Effect of Constituents ........................................................................................... 29-30 Corrosive Attack ................................................................................................... 30-31 Groups of Corrosion-Resistant Alloy Castings ..................................................... 31-33

Martensitic Alloys (CA-15, CA-40, CA-6NM, CA-6N)

Ferritic and Duplex Alloys (CB-30, CC-50, CD-4MCu)

Austenitic Alloys (CE-30, CF types, CG-8M, CH-20, CK-20, CN-7M, CN-7MS, IN-862)

Precipitation Hardenable Alloys (CB-7Cu-1, CB-7Cu-2)

Nickel-Base Alloys (CZ-100, M-35, CY-40, Alloy 625, CW-12M, N-12M, Ni-Si)

Corrosion Data ..................................................................................................... 34-37 Industrial Applications of Corrosion-Resistant Alloy Castings .............................. 38-48

Aeronautical .......................................................................................................... 38

Architectural .......................................................................................................... 38

Chemical & Petroleum ....................................................................................... 39-40

Process Industries Equipment ........................................................................... 41-44

Hydraulics .............................................................................................................. 45

Marine ................................................................................................................... 44

Power–Nuclear & Conventional ........................................................................ 45-48

Part Ill. Fabrication Data for Heat & Corrosion-Resistant Alloy Castings .... 49-52

Machining ............................................................................................................. 49-51

Welding ................................................................................................................. 51-52

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The heat-resistant casting alloys are those composi-tions that contain at least 12% chromium which are capable of performing satisfactorily when used at tem-peratures above 1200 ºF. As a group, heat-resistant compositions are higher in alloy content than the corrosion-resistant types. The heat-resistant alloys are composed principally of nickel, chromium and iron to-gether with small percentages of other elements. Nickel and chromium contribute to the superior heat resistance of these materials. Castings made of these alloys must meet two basic requirements:

1. Good surface film stability (oxidation and corro-sion resistance) in various atmospheres and at the temperature to which they are subjected.

2.Sufficient mechanical strength and ductility to meet high temperature service conditions.

The heat-resistant alloys are listed in Table I along with their chemical compositions and designations. Commercial cast heat-resistant alloys can be identified by designations of the Alloy Casting Institute, now a division of the Steel Founders' Society of America, and the American Society for Testing and Materials.* Some of these materials are also listed in the Aerospace Mate-

*See ASTM Specification A 297

rial Specifications (AMS) of the Society of Automotive Engineers, United States Government Military Specifi-cations (MIL), the Society of Automotive Engineers Specifications and the Unified Numbering System (UNS) developed by the Society of Automotive Engi-neers and the American Society for Testing and Mate-rials. Standard ACI designations are listed in Table I.

The Alloy Casting Institute designations use "H" to indicate alloys generally used in applications where the metal temperature exceeds 1200 ºF. The second letter indicates the nominal nickel content, increasing from A to X.

The chemical compositions of the heat-resistant cast-ing alloys are not the same as those of the wrought alloys. Therefore, Table I lists only the nearest wrought alloy AISI type number. Alloy Casting Institute designa-tions or their equivalents should always be used when identifying castings.

The SAE specification designations use the nearest wrought composition (AISI type number) and prefix it with the number 70 ºFor heat-resistant castings: for example, 70310 is equivalent to HK. In the Unified Num- bering System, the Jxxxx number series is assigned to cast steels.

TABLE I

Compositions of Heat-Resistant Alloy Castings

CHEMICAL COMPOSITION, % Alloy Casting Institute

Designation

Alloy Type

ASTM Specification

Nearest AISI Type

UNS No. Ni Cr C Mn

max Si

max Mo max

Other

HA 8-10Cr A217 – – – 8-10 0.20 max 0.35-0.65 1.00 0.90-1.20 Fe bal HC 28Cr A297 446 J92605 4 max 26-30 0.50 max 1.00 2.00 0.5 Fe bal HD 28Cr-6Ni A297 327 J93005 4-7 26-30 0.50 max 1.50 2.00 0.5 Fe bal HE 28Cr-9Ni A297 312 J93403 8-11 26-30 0.20-0.50 2.00 2.00 0.5 Fe bal HF 19Cr-9Ni A297 302B J92603 9-12 19-23 0.20-0.40 2.00 2.00 0.5 Fe bal HH 25Cr-12Ni A297, A447 309 J93503 11-14 24-28 0.20-0.50 2.00 2.00 0.5 Fe bal HI 28Cr-15Ni A297 – J94003 14-18 26-30 0.20-0.50 2.00 2.00 0.5 Fe bal HK 25Cr-20Ni A297, A351

A567 310 J94224 18-22 24-28 0.20-0.60 2.00 2.00 0.5 Fe bal

IN-5191 24Cr-24Ni – – – 23-25 23-25 0.25-0.35 1.00 1.00 – Cb 1.4-1.8; Fe bal HL 30Cr-20Ni A297 – J94604 18-22 28-32 0.20-0.60 2.00 2.00 0.5 Fe bal HN 25Ni-20Cr A297 – J94213 23-27 19-23 0.20-0.50 2.00 2.00 0.5 Fe bal HP 35Ni-26Cr A297 – J95705 33-37 24-28 0.35-0.75 2.00 2.00 0.5 Fe bal

HP-50WZ 35Ni-26Cr – – – 33-37 24-28 0.45-0.55 2.00 2.50 – W 4-6; Zr 0.1-1.0; Fe balHT 35Ni-17Cr A297, A351 330 J94605 33-37 15-19 0.35-0.75 2.00 2.50 0.5 Fe bal HU 39Ni-18Cr A297 – J95405 37-41 17-21 0.35-0.75 2.00 2.50 0.5 Fe bal HW 60Ni-12Cr A297 – – 58-62 10-14 0.35-0.75 2.00 2.50 0.5 Fe bal HX 66Ni-17Cr A297 – – 64-68 15-19 0.35-0.75 2.00 2.50 0.5 Fe bal

Chromium Nickel 50Cr-5ONi A560 – – bal 48-52 0.10 max 0.30 1.00 – Fe 1.0 max IN-6571 50Cr-48Ni – – – bal 48-52 0.10 max 0.30 0.50 – Cb 1.4-1.7; N 0.16 max;

Fe 1.0 max 1INCO Designation

Part I Heat-Resistant Alloy Castings

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EFFECT OF CONSTITUENTS

Nickel

Nickel is present in cast heat-resistant alloys in amounts up to 70%. Its principal function is to strengthen and toughen the matrix. Microstructurally, nickel promotes the formation of austenite which is stronger and more stable at elevated temperatures than ferrite. Nickel contributes to resistance to oxidation, car-burization, nitriding and thermal fatigue.

Chromium

The chromium content in heat-resistant alloys varies from approximately 10 to 30%. Chromium imparts resis-tance to oxidation (scaling) at elevated temperatures, and to sulfur-containing atmospheres. Also, chromium carbides precipitate in the matrix and contribute to high-temperature creep and rupture strength. In some alloys, chromium increases resistance to carburization. It also improves the resistance of the alloys to the action of many other corrosive agents at normal and elevated temperatures. It promotes the formation of ferrite in the microstructure.

Other Elements

Nickel and chromium have the greatest effect on the properties of heat-resistant castings but the minor alloy-ing elements also influence the properties.

Carbon content ranges from 0.20 to 0.75%. It pro-motes dispersion-strengthening through the formation of carbide in the structure. Increasing the carbon content improves the high-temperature strength and creep resistance of the heat-resistant alloys at the expense of lower ductility.

Silicon has a beneficial effect on the high-temperature corrosion resistance and on resistance to carburization. In amounts greater than 2%, it lowers the high-temperature creep and rupture properties and, in general, the silicon content is limited to 1.5% in castings intended for service above 1500 ºF. Silicon promotes the formation of ferrite.

Manganese, although important in melting opera-tions, has little or no effect on the mechanical properties or corrosion resistance when present in moderate amounts.

Molybdenum improves the high-temperature creep and rupture strength by promoting stabilization of car-bides. In some instances, it also increases high-temperature corrosion resistance. It slightly increases resistance to carburization.

Work to improve the creep and stress rupture proper-ties of the heat resisting chromium-nickel-iron alloys through the addition of small amounts of tungsten, zirco-nium, titanium, columbium, nitrogen, or combinations of them, has been pursued for several years under Steel Founders' Society of America sponsorship and by

others in the United States, Japan and Britain. Alteration of the carbide morphology from lamellar to discrete particles seems to be the important factor; HP-50WZ (Table I) and IN-657 (Tables I through IV) are examples of commercial alloys with improved property levels.

INFLUENCE OF MICROSTRUCTURE

The iron-chromium-nickel heat-resistant alloys de-signed for service up to 1200 ºF often have mixed ferriteaustenite matrices. However, alloys intended for service above 1200 ºF are austenitic. The compositions of these alloys are generally adjusted to prevent the for-mation of ferrite which has a detrimental effect on high-temperature creep-rupture strength. Long-time expo-sure at high temperatures, e.g., 1500 ºF, can result in transformation of ferrite to the sigma phase with signifi-cant loss of toughness at room temperature. Thus, in these alloys, the high-temperature strength is based primarily on the solid solution strengthening of the aus-tenite by the addition of nickel, chromium and certain minor elements.

Carbides also contribute to strengthening these al-loys. As noted previously, these alloys have carbon contents ranging from 0.20 to 0.75%. In the as-cast condition, the microstructures consist of carbides dis-persed in an austenite matrix which also contains dis-solved carbon. By interfering with dislocation move-ment, these precipitated carbides assist in strengthen-ing the alloy. During long service at elevated tempera-tures in the range 1000 to 1800 ºF, additional chromium carbides precipitate in finely divided form and also as-sist in strengthening the alloys. At temperatures some-what above 1800 ºF, the primary carbides have a ten-dency to coalesce and the secondary carbides to redis-solve in the matrix. Nickel and chromium retard this tendency.

GROUPS OF HEAT-RESISTANT ALLOY CASTINGS

The heat-resistant alloys can be classified according to composition and metallurgical structure into three broad groups:

1. Chromium-iron alloys: HA, HC, HD. 2. Chromium-nickel-iron alloys: HE, HF, HH, HI, HK,

IN-519, HL. 3. Nickel-chromium-iron alloys: HN, HP, HT, HU, HW,

HX.

In addition, chromium-nickel heat-resistant alloys in-clude 50Cr-50Ni and IN-657.

A general discussion of each group is followed by a discussion of each alloy.

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CHROMIUM-IRON ALLOYS

This group consists of alloys in which chromium pre-dominates with up to 30% chromium and up to 7% nickel. These alloys are ferritic and have relatively low hot strength. They are seldom used in critical loadbearing parts at temperatures above 1400 ºF, but have found use in applications involving uniform heating and certain atmospheric conditions, such as high-sulfur atmospheres. The alloys in this group include the HA, HC and HD types.

HA (9Cr)

Type HA is a chromium-molybdenum-iron alloy that is resistant to oxidation up to about 1200 ºF. The molyb-denum content contributes desirable strength properties to the alloy at these moderate temperatures. Typical uses are furnace rollers, Lehr rolls, refiner fittings and trunnions.

HC (28Cr-4Ni max)

The HC type is limited to applications where strength is not a consideration or for moderate load-bearing service around 1200 ºF. It provides excellent resistance to oxidation and flue gases containing sulfur at tempera-tures as high as 2000 ºF. It is also used where high nickel content tends to crack hydrocarbons through catalytic action. Due to the low nickel content, the ductility and impact toughness are very low at room temperatures and the creep strength is very low at elevated tempera-tures. Typical uses are boiler baffles, furnace grate bars, kiln parts, recuperators, salt pots and tuyeres.

HD (28Cr-6Ni)

The HD type has the best hot strength, weldability and high-temperature corrosion resistance of the chromium-iron group. HD can be used for load-bearing applications up to 1200 ºF, and where only light loads are involved up to 1900 ºF. It is suitable for use in high-sulfur atmospheres. Long exposures to temperatures in the range 1300 to 1500 ºF may in some cases result in considerable hardening, accompanied by a severe loss of room temperature ductility through the formation of the sigma phase. Typical applications are roaster fur-nace rabble arms and blades, salt pots and cement kiln ends.

CHROMIUM-NICKEL-IRON ALLOYS

These alloys are characterized by good high-temperature strength, hot and cold ductility, and resis-tance to oxidizing and reducing conditions. They are useful for atmospheres high in sulfur, particularly under reducing conditions. These alloys contain 8 to 22% nickel and 18 to 32% chromium, and may have either a partial or a completely austenitic microstructure. They include types HE to HL.

HE (28Cr-9Ni)

This type has excellent high-temperature corrosion

resistance and is frequently recommended for service in sigh-sulfur atmospheres where alloys containing higher nickel cannot be used. Because of its high alloy content, it is suitable for use up to 2000 ºF. The alloy has moder-ately high hot strength and excellent ductility. It is widely used for parts such as conveyors in furnaces, recupera-tors, coke oven exhaust castings, roasting furnace cen-ter shafts and tube support castings. Prolonged expo-sure at temperatures around 1500 ºF may promote for-mation of the sigma phase with consequent low ductility at room temperature.

HF (19Cr-9Ni)

This type is comparable to the popular wrought corrosion-resisting 18-8 compositions and is suitable for use up to around 1600 ºF. It approaches the HH grade in many properties and combines moderately high hot strength and ductility. Its microstructure is essentially austenitic. Typical uses include burnishing and coating rolls, furnace dampers, annealing furnace parts, etc.

HH (25Cr-12Ni)

This type is one of the most popular of the heat-resistant alloys and accounts for about one-fifth of all heat-resistant casting production. This alloy contains the minimum quantities of chromium and nickel to sup-ply a useful combination of strength and corrosion resis-tance for elevated temperature service above 1600 ºF. The chromium range is high enough to assure good scaling resistance up to 2000 ºF in air or normal products of combustion. Sufficient nickel is present, aided by carbon, nitrogen and manganese, to maintain austenite as the major phase; however, the microstructure is sensitive to composition balance. For high ductility at 1800 ºF, a two-phase structure of austenite and ferrite is appropriate but such a structure has lower creep strength If high creep strength is needed and lower ductility can be tolerated, a composition balanced to be completely austenitic is desirable.

Alloy HH is covered by ASTM specification A 447 which recognizes two types. Type I is partially ferritic and Type II predominately austenitic. Type I has a max-imum magnetic permeability of 1.70 and Type II of 1.05.

Because of its high creep strength and relatively low ductility, Type II is useful in parts subject to high constant load conditions in the range from 1200 to 1800 ºF Some typical uses are for furnace shafts, beams, rails and rollers, tube supports and cement and lime kiln ends. Type I alloy is used where hot ductility is more important than hot strength, and is preferred for welding.

Both types of HH alloy have good resistance to sur-face corrosion under the various conditions encoun-tered in industry, but are seldom used for carburizing applications because of embrittlement caused by ab-sorption of carbon. Experience has indicated that HH alloys can withstand repeated temperature changes or differentials reasonably well; however, they are not gen-erally recommended for severe cyclic service such a

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HI (28Cr-15Ni)

This alloy is resistant to oxidation up to 2150 ºF. Its composition is such that it is more likely to be completely austenitic than the lower alloys of this group, hence it has more uniform high-temperature properties. This type is used for billet skids, conveyor rollers, furnace rails, lead pots, retorts for magnesium production, hearth plates and tube spacers.

HK (25Cr-20Ni)

The HK alloy provides one of the most economical combinations of strength and surface stability at tem-peratures up to and above 1900 ºF and accounts for almost half of the heat-resistant alloy tonnage.

It can be used in structural applications up to 2100 ºF but is not recommended where severe thermal shock is a factor. It is used for parts where high creep and rupture strengths are needed such as steam methane reformer tubing, ethylene pyrolysis tubing, gas turbines, furnace door arches and chain, brazing fixtures, cement kiln nose segments, rabble arms and blades, radiant tubes, retorts and stack dampers.

IN-519 (24Cr-24Ni-1.5Cb)

This alloy is a modification of HK alloy in which the 25-20 base has been altered, the carbon content has been reduced and columbium (niobium) has been added. As a result, the high-temperature stress-rupture strength has been improved. It is used for centrifu-gally-cast catalyst tubes in steam-hydrocarbon re-former furnaces.

HL (30Cr-20Ni)

This alloy has excellent resistance to oxidation at temperatures over 2000 ºF, and is resistant to corrosion in flue gases containing a moderate amount of sulfur up to 1800 ºF. It is used where higher strength is required than obtainable with lower nickel content alloys. Leading applications are for radiant tubes, furnace skids and stack dampers where excessive scaling must be avoided, such as in enameling furnace carriers and fixtures.

NICKEL-CHROMlUM-IRON ALLOYS

The nickel-chromium-iron alloys are fully austenitic and contain 25 to 70% nickel and 10 to 26% chromium. They can be used satisfactorily up to 2100 ºF because no brittle phase forms in these alloys. They have good weldability and are readily machinable if proper tools and coolants are used. The specific types of alloys in this group are HN, HP, HT, HU, HW and HX.

These austenitic heat-resistant alloys have good hot strength and good resistance to carburization and thermal fatigue. They are used widely for load-bearing appli-cations and for castings subject to cyclic heating and large temperature differentials. They will withstand re-ducing and oxidizing atmospheres satisfactorily but high-sulfur atmospheres should be avoided.

HN (25Cr-20Ni)

This alloy has properties somewhat similar to the more widely used HT alloy but has better ductility. It is used for highly stressed components in the 1800-2000 ºF range. It has also given satisfactory ser-vice in several specialized applications, notably brazing fixtures at temperatures up to 2100 ºF. Among its appli-cations are chain, furnace beams and parts, pier caps, brazing fixtures, radiant tubes, tube supports and torch nozzles.

HP (35Ni-26Cr)

This alloy is related to the HN and HT types but contains more nickel than the HN alloy and more chro-mium than the HT alloy. This composition makes the HP alloy resistant to both oxidizing and carburizing atmo-spheres at high temperatures and provides high stress-rupture properties in the range 1800-2000 ºF. It is used for ethlene pyrolysis tubing, steam methane reformer tubing, heat treating fixtures and radiant tubes. Several proprietary modifications containing columbium and/or tungsten are also being used.

HT (35Ni-17Cr)

About one-seventh of the total production of heat-resistant castings is HT alloy because of its value in resisting thermal shock, its resistance to oxidation and carburization at high temperatures, and its good strength at heat treating furnace temperatures. Except in high-sulfur gases, it performs satisfactorily up to 2100 ºF in oxidizing atmospheres and up to 2000 ºF in reducing atmospheres. It is used for load-bearing mem-bers in many furnace applications, retorts, radiant tubes, cyanide and salt pots, hearth plates and trays quenched with the work.

HU (39Ni-18Cr)

This type has an exceptionally high combination of creep strength and ductility up to 2000 ºF and is used where high hot strength is required. It is suited for severe service conditions involving high stress and rapid thermal cycling. HU alloy has good resistance to corrosion by either oxidizing or reducing hot gases containing moderate amounts of sulfur. Typical uses are heat treat-ing salt pots, quenching trays, fixtures and gas dissocia-tion equipment.

HW (60Ni-12Cr)

The HW alloy performs satisfactorily up to 2050 ºF in strongly oxidizing atmospheres and up to 1900 ºF in oxidizing or reducing products of combustion, provided that sulfur is low or not present in the gas. The adherent nature of its oxide scale makes HW alloy suitable for enameling furnace service where even small flecks of dislodged scale could ruin the work in process. High-temperature strength, resistance to thermal fatigue and resistance to carburization, are obtainable with this alloy and its high electrical resistivity suits it for electrical

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heating elements. Other applications are cyanide pots, gas retorts, hardening fixtures (quenched with the work), hearth plates, lead pots, muffles and other parts in cyaniding and carburizing operations. HX (66Ni-17Cr)

The high-alloy content of this grade confers high re-sistance to hot gas corrosion even in the presence of some sulfur and permits it to be used for severe service applications where corrosion must be minimized at tem-peratures up to 2100 ºF. It is used to great advantage where maximum and widely fluctuating temperatures are encountered because of its ability to withstand cycling without cracking or severe warping. Thus, a leading application is for quenching fixtures. It is also useful in carburizing and cyaniding equipment. Typical applica-tions in which it gives excellent service include nitriding, carburizing and hardening fixtures (quenched with the work), heat-treating boxes, retorts and burner parts.

CHROMIUM NICKEL ALLOYS

Chromium-Nickel Alloy (50Cr-50-Ni)

This alloy was developed to improve the resistance of heat-resistant alloys to fuel oil ash. It is widely used worldwide (and in fact is specified almost exclusively in Europe) for resistance to oil ash corrosion in power plants, petroleum refinery heaters and marine boilers at temperatures up to about 1650 ºF. Its applications in-clude such parts as sidewall and roof hanger supports in-furnace radiant sections, tube sheets, re-radiation cone tips in vertical furnaces and for burner parts.

IN-657 (50Cr-48Ni-1.5Cb)

This more recent development is a columbium (niobium) modification of the 50Cr-50Ni alloy also with high resistance to fuel oil ash corrosion but with creep and stress-rupture properties superior to those of the 50Cr-50Ni alloy. IN-657 is used in petroleum refinery heaters, marine and land-based boilers in such applica-tions as convection section tube sheets; it is produced by several U.S. and European foundries under license from Inco.*

properties that must be matched with them. Some of these properties are listed below and are discussed later under "Alloy Casting Design."

Operating Conditions Related Property

1. Anticipated service and maximum temperature of operation

Short-time tensile properties Creep strength Stress-rupture properties Hot ductility

2. Type and size of maximum load Short-time tensile properties Creep strength Stress-rupture properties Hot ductility

3. Temperature cycling a. Range of temperature cycling b. Frequency of temperature cycling c. Rate of temperature change

Thermal fatigue properties

4. Type of atmosphere or other corrosive conditions

Oxidation resistance Carburization resistance Sulfidation resistance Surface stability

5. Size and shape of part Temperature gradients

6. Further processing, such as welding and machining

Fabrication data

7. Abrasive or wear conditions – 8. Cost – 9. Ease of replacement –

The governing economic consideration in the selec-tion of heat-resistant alloy castings is the cost per hour at operating temperatures. Equipment downtime can result in a loss of production that is far more expensive than the cost of the alloy involved. Ease of replacement

must also be considered in the selection of the alloy. With rare exceptions, the use of heat-resistant alloys is justified at all temperatures above 1200 ºF.

In selecting heat-resistant alloys for castings, the sig-nificant properties that must be considered are shown in Tables II, III and IV.

*Trademark of the Inco family of companies.

SELECTING THE PROPER ALLOY The selection of the proper cast alloy for a given

high-temperature application requires knowledge of various factors and the related mechanical and physical

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HEAT-RESISTANT ALLOY CASTING DESIGN

The properties listed in Table II and Figures 1 through 4, inclusive, are the basis for the design of heat-resistant alloy castings. This selection is concerned with the ap-

plication of these properties in casting design together with other design considerations that are not amenable to tabulation.

TABLE II Room Temperature Mechanical Properties of Heat-Resistant Alloy Castings

1Annealed 2Normalized at 1825 ºF and tempered at 1250 ºF. 30.2% Proof Stress 4Minimum

HIGH-TEMPERATURE MECHANICAL PROPERTIES son of alloys, and Table III shows the data on this basis.

This is sometimes expressed as 1 % creep in 10,000 hr. It should be kept in mind that when creep is expressed in the latter terms it does not mean that this rate of creep can be expected to continue in every instance for 10,000 hours without failure.

Figure 1 and Table III compare the creep strengths of representative heat-resistant alloy castings.

Creep values that are obtained under constant load and constant temperature conditions are applicable to design, however, safety factors should always be incor-porated. The safety factor will depend on the degree to which the application is critical.

Stress-Rupture Properties

Stress-rupture properties determined under constant load at constant temperature are useful in approximating the life of the alloy (time to fracture) under the specific conditions and also for comparing alloys which are subject to loading that might produce failure in a relatively short time.

In common with all metals, the load-carrying ability of heat-resistant casting alloys decreases as the tempera-ture increases. However, the fall-off in strength is less pronounced than it is with less highly alloyed materials.

At elevated temperatures, metals under stress are subject to slow plastic deformation as well as to elastic deformation. Therefore, time becomes a critical factor and conventional tensile tests do not furnish values that are useful in design. The data required are those indica-ting the load which will produce no more than an allow-able percentage of elongation at a specified tempera-ture in a given period of time. Thus, the factors of time and deformation as well as stress and temperature are involved in high-temperature strength properties.

Creep Strength

The slow plastic deformation that occurs under load at elevated temperatures is known as creep. In the design of furnace parts, experience indicates that a creep rate of 0.0001% per hr is satisfactory for compari-

PROPERTY HA HC HD HE HF Type I

HH Type II

HH HI HK IN- 519 HL HN HP HT HU HW HX

50Cr-50Ni

IN 657

Tensile Strength, ksi As-Cast 951 70 85 95 92 85 80 80 75 75 82 68 71 70 70 68 65 804 87 Aged 1072 115 – 90 100 86 92 90 85 – – – – 75 73 84 73 – –

Yield Strength (0.2% offset), ksi As-Cast 651 65 48 45 45 50 40 45 50 353 52 38 40 40 40 36 36 504 543 Aged 812 80 – 55 50 55 45 65 50 – – – – 45 43 52 44 – –

Elongation in 2 in., % As-Cast 231 2 16 20 38 25 15 12 17 25 19 13 11.5 10 9 4 9 15 28 Aged 212 18 – 10 25 11 8 6 10 – – – – 5 5 4 9 – –

Brinell Hardness As-Cast 1801 190 190 200 165 185 180 180 170 – 192 160 – 180 170 185 176 – – Aged 2202 - – 270 190 200 200 200 190 – – – – 200 190 205 185 – –

Aging Treatment - 24 hours at

1400 ºF Furnace Cooled

– 24 hours at


24 hours at


24 hoursat

1400 ºFFurnaceCooled

24 hoursat


24 hoursat

1400 ºF FurnaceCooled

24 hoursat


– – – – 24 hours at

1400 ºF Air

Cooled

48 hours at

1800 ºF Air

Cooled

48 hoursat


48 hoursat

1800 ºFAir

Cooled

– –

Modulus of Elasticity in Tension, ksi x 103

29 29 27 25 28 27 27 27 27 23 27 27 27 27 27 25 25 – 30

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TABLE III

Elevated Temperature Properties of Heat-Resistant Alloy Castings

11470 ºF 41290 ºF 21650 ºF 52010 ºF 31830 ºF 61110 ºF

Stress-rupture properties are a valuable adjunct to creep-strength values in the selection of heat-resistant casting alloys and in the establishment of allowable design stresses. Figures 2, 3, and 4 compare the stress-rupture properties of representative casting alloys for various time periods. Frequently, designers of furnaces and furnace tubing use the 100,000-hour stress-rupture properties with some factor of safety. A comparison of Figures 1 and 2 shows that, in general, stress-rupture tests rank the alloys in much the same order as the creep tests.

Ductility An accurate comparison of hot ductility of heat-

resistant casting alloys is difficult since there is no gen-erally accepted reference test. Total elongation values on both creep and stress-rupture tests are often used as criteria. Also, the elongation in short-time high-temperature tensile tests is commonly used in specifica-tions as an indication of high-temperature ductility. In many applications where castings are handled at normal temperatures, room temperature ductility is a con-sideration. Heat treating to remove sigma phase by heating castings to 1800 ºF and cooling to below 1200 ºF improves ductility.

PROPERTY HA HC HD HE HF Type l

HH Type II

HH HI HK IN-519 HL HN HP HT HU HW HX 50Cr-50Ni IN-657Short-Time Tensile Strength, ksi, at

1000 ºF 67 – – – – – – – – – – – – – – – – 446 866 1200 ºF – – – – 60 – 60.5 – – – – – – 42.4 – – 45 404 794 1400 ºF – – 36 – 38 33 37.4 38 37.5 391 50 – 43 35 40 32 – 361 681 1600 ºF – – 23 – 21 18.5 21.5 26 23.3 232 30.4 20.2 26 18.8 19.6 19 20.5 182 362 1800 ºF – – 15 – – 9 10.9 – 12.4 153 18.7 11.9 14.5 11 10 10 10.7 – – 2000 ºF – – – – – – 5.5 – 5.6 – 6.2 7.5 6 – – – – –

Short-Time Yield Strength (0.2% Offset), ksi, at

1000 ºF 42 – – – – – – – – – – – – – – – – – 366 1200 ºF – – – – 31.5 – 32.2 – – – – – – 28 – – 20 – 464 1400 ºF – – – – 25 17 19.8 – 24.4 201 – – 29 26 – 23 – – 291 1600 ºF – – – – 15.5 13.5 16 – 14.7 132 – 14.5 17.5 15 – 15 17.5 – 152 1800 ºF – – – – – 6.3 7.3 – 8.7 93 – 9.6 11.0 8 6.2 8 6.9 – – 2000 ºF – – – – – – – – 5.0 – – 4.9 6.2 – – – – – –

Elongation in 2 in., %, at

1000 ºF – – – – – – – – – – – – – – – – – 126 166 1200 ºF – – – – 10 – 14 – – – – – – 5 – – 8 44 154 1400 ºF – – 14 – 16 18 16 6 12 321 – – 15 10 – – – 31 151 1600 ºF – – 18 – 16 30 18 12 16 432 – 37 27 26 20 – 48 52 192 1800 ºF – – 40 – – 45 31 – 42 373 – 51 46 28 28 40 40 – – 2000 ºF – – – – – – – – 55 – – 55 69 – – – – – –

Creep Stress 0.0001%/hr, ksi, at

1000 ºF 16 – – – – – – – – – – – – – – – – – – 1200 ºF 3.1 – – – 18 – 18 – – – – – – – – – – – 184 1400 ºF – 1.3 3.5 4 6.8 3 6.3 6.6 10.2 8.61 7.0 – – 8 8.5 6 6.4 – 6.51

1600 ºF – 0.75 1.9 2.4 3.9 1.7 3.9 3.6 6.0 4.52 4.3 6.3 5.8 4.5 5.0 3 3.2 – 2.52

1800 ºF – 0.36 0.9 1.4 – 1.1 2.1 1.9 2.5 1.83 2.2 2.4 2.8 2 2.2 1.4 1.6 – 0.53

2000 ºF – – 0.2 0.4 – 0.3 0.8 0.8 0.65 – – 1.0 1.0 0.5 0.6 – 0.6 – – 2150 ºF – – – – – – – 0.15 – – – – – 0.15 – – – – –

Stress to Rupture in 100 hr, ksi, at

1000 ºF 37 – – – – – – – – – – – – – – – – – – 1200 ºF – – – – 33 – 35 – – – – – – – – – – – 304 1400 ºF – 3.3 10 11 13.5 14 14 13 15.5 141 15.0 – – 16 15 10 13 – 14.51

1600 ºF – 1.7 5 5.3 7.2 6.4 6.8 7.5 9.2 92 9.2 11 10 8.9 8 6 6.7 – 7.22

1800 ºF – 0.85 2.5 2.5 – 3.1 3.2 4.1 4.7 53 5.2 5.6 5.9 4.4 4.5 3.6 3.5 – 3.83

2000 ºF – – – – – 1.5 1.4 1.9 2.2 – – 2.9 2.8 2.1 – – 1.7 – 1.65

11

Figure 1– Creep Strength of Heat-Resistant Alloy Castings (HT curve is included in both graphs for ease of comparison).

12

Figure 2 –1,000-Hour Stress-Rupture Properties of Heat-Resistant Alloy Castings (HT curve is included in both graphs for ease of comparison).

13

Figure 4–100,000-Hour Stress-Rupture Properties of Several Heat-Resistant Alloy Castings.

14

Short-Time Tensile Properties

Short-time hot-tensile tests in which the test speci-men is held at the test temperature for one hour and then pulled at temperature, cannot be relied upon to indicate how heat-resistant alloys will behave in service. The values obtained are as much as five or six times the limiting creep stress values, and, therefore, greatly over-evaluate load-carrying ability over long periods of time. Nevertheless, short-time tensile tests can be help-ful in evaluating resistance to momentary overloads and are included in some specifications. The short-time mechanical properties for the standard heat-resistant alloys are given in Table Ill.

Thermal Fatigue

In many high-temperature applications, intermittent or widely fluctuating temperatures (cyclic heating) are encountered, and therefore the ability of the various heat-resistant casting alloys to withstand such thermal fatigue service must be considered.

Thermal fatigue failure involves cracking caused by heating and cooling cycles. Crazing and checking of heat-treating fixtures are typical examples. Such fail-ures are the result of many reversals of thermal stresses in the part as contrasted to common mechanical fatigue failures, which are caused by externally applied loads.

Very little experimental thermal fatigue information is available on which comparison of the various alloys can be based, and no standard test as yet has been adopted. Field experience indicates that, usually, resis-tance to thermal fatigue is improved with increasing nickel content. Columbium-modified ACI alloys have been employed successfully where a high degree of thermal fatigue resistance is desired such as in reformer outlet headers.

Temperature Gradients

Non-uniform heating or cooling causes temperature gradients and the attendant unequal dimensional changes result in stresses within the casting, These stresses may be accompanied, particularly at high tem-peratures, by some degree of plastic deformation. The magnitude of the stress and/or the amount of the plastic deformation will depend on the temperature differential within the casting.

Heat-resistant alloys inherently have high coefficients of thermal expansion and low heat conductivity, both properties tending to produce temperature and stress differences between various regions of a casting. The unequal stresses set up within the casting tend to distort or fracture it; thus, maximum articulation should be de-signed into elevated temperature parts by making them of a number of small components that are free to expand and contract. All sharp corners and abrupt changes in section are to be avoided.

Proper design, taking all thermal conditions into con-sideration, is as important as alloy composition in deter-

mining the life of castings in service. For this reason, the heat-resistant casting user should consult with the pro-ducers in the early stages of design in order to obtain the benefit of their experience with similar applications.

DESIGN DATA

The curves shown in Figure 5 are constructed to indicate the values of allowable stress that result from applications of code criteria to the short-time tensile, creep, and stress-rupture properties of the heat-resistant alloys, HF, HH-II, HK and HN. The ASME Boiler Code allowable stresses for wrought composi-tions are included in two of the graphs to offer a compari-son.

HIGH-TEMPERATURE CORROSION RESISTANCE

High-temperature equipment is exposed to many dif-ferent atmospheres and corrosive conditions and an important requirement of heat-resistant alloys is surface film stability. No single alloy will show satisfactory resis-tance to all of the high-temperature environments.

High-temperature corrosive conditions may involve simple oxidizing or reducing atmospheres or they may be complicated by sulfur compounds in the products of combustion. Oxidizing flue gases are slightly more cor-rosive than air if the sulfur concentration is low. Corro-sive attack by reducing flue gases is similar to that of an oxidizing gas if the sulfur content is not greater than 100 ppm. At higher sulfur concentrations, attack by reducing gas is much more severe. The high nickel alloys, types HN to HW, give good service under oxidizing and reduc-ing conditions if the sulfur content of the gas is low. Types HH and HL, for example, should be considered for service in sulfur-bearing atmospheres.

Cyclic heating under reducing conditions increases metal loss in alloys containing from 10 to 50% nickel. Under oxidizing conditions, cyclic heating has little ef-fect in alloys containing more than 20% nickel.

Different corrosive conditions are encountered with equipment in contact with fused salts or molten metals. Types HT to HX should be considered for service under these conditions. Still other conditions are met in the chemical, petroleum, and petrochemical industries where new processes with new corrosive conditions are constantly under development.

In the heat-treating industry, only the high nickel-chromium alloys give satisfactory service under nitriding conditions. Another important process in the heat-treating industry is carburization, which is considered in some detail below.

Carburization Resistance

When heat-resistant castings are used as muffles, holding fixtures or baskets for work being carburized,

15

Figure 5–Design Data for Four Heat-Resistant Steels.

16

the castings also pick up carbon. The same effect oc-curs in any high-temperature carbon-bearing atmo-sphere under reducing conditions. Some alloys absorb from 0.30 to 2% carbon within a period of several months when used in a carburizing application. A large increase in carbon pickup leads to volume changes which can cause warpage and distortion. The additional carbon also leads to difficulties if repair welding of the casting is necessary. Increasing the nickel content re-duces the effect of increased carbon content on the mechanical properties of heat-resistant alloys. Hence, the nickel-chromium-iron grades HP to HX are preferred because they withstand thermal fatigue and shock load-ing at higher carbon levels than alloys with less nickel.

Resistance to carbon penetration increases as the nickel content increases and to some extent as the chromium content increases. Therefore the high nickel types HP to HX are all good in this respect with the HW and HX types, being highest in nickel content, rating as excellent.

The high chromium types are generally not suitable for service under carburizing conditions unless other requirements dictate their selection. In such cases, sili-

con content should be kept on the high side. Carburiza-tion resistance of types HH and HK is improved with silicon content above 1.6%.

ROOM TEMPERATURE PROPERTIES

The room temperature properties of the various alloys shown in Table II have little relationship to high-temperature behavior. These properties are useful only for acceptance purposes and for instances where the nature of the service requires good strength at room temperature.

Acceptance tests of a particular composition at room temperature are used only with the supposition that the alloy will behave at elevated temperatures in the same way that the same composition has behaved previously in the same application.

The room temperature properties after aging are given as an indication of the structural stability of the alloy after high-temperature exposure.

The physical properties of the heat-resistant alloys are given in Table IV.

TABLE IV Physical Properties of Heat-Resistant Alloy Castings

Property HA HC HD HE HF Type l

HH

Type II

HH HI HK IN-519 HL HN HP HT HU HW HX

50Cr-50Ni

IN 657

Density, lb/cu in. 0.279 0.272 0.274 0.277 0.280 0.279 0.279 0.279 0.280 0.286 0.279 0.283 0.284 0.286 0.290 0.294 0.294 0.291a 0.288

Mean Coefficient of Linear Thermal Expansion, in./in./° F x 10-6

70 - 212 ºF 6.1 - - - - - - - - 7.21 - - - 7.9 - 7.0 - - 5.91 70 - 1000 ºF 7.1 6.3 7.7 9.6 9.9 9.5 9.5 9.9 9.4 9.12 9.2 9.3 9.2 8.8 8.8 7.9 7.8 7.42 70- 1200 ºF 7.5 6.4 8.0 9.9 10.1 9.7 9.7 10.0 9.6 - 9.4 9.5 9.5 9.1 9.0 8.2 8.1 - 70 - 1400 ºF - 6.6 8.3 10.2 10.3 9.9 9.9 10.1 9.8 9.33 9.6 9.7 9.8 9.3 9.2 8.5 8.5 8.33 70 - 1600 ºF - 7.0 8.6 10.5 10.5 10.2 10.2 10.3 10.0 9.44 9.7 9.9 10.0 9.6 9.4 8.7 8.8 8.34 70 - 1800 ºF - 7.4 8.9 10.8 10.6 10.5 10.5 10.5 10.2 9.55 9.9 10.1 10.3 9.8 9.6 9.0 9.2 8.25 70 - 2000 ºF - 7.7 9.2 11.1 10.7 10.7 10.7 10.8 10.4 - 10.1 10.2 10.6 10.0 9.7 9.3 9.5 -

1200 - 1600 ºF - 8.7 10.3 12.2 11.5 11.4 11.4 11.0 - - 10.5 - 11.4 10.8 10.5 10.0 10.7 - 1200 - 1800 ºF - 9.3 10.6 12.5 - 11.7 11.7 12.0 11.4 - 10.7 11.0 11.9 11.0 10.6 10.3 11.3 -

Specific Heat, Btu/Ib/° F at 70 ºF 0.11 0.12 0.12 0.14 0.12 0.12 0.12 0.12 0.13 0.11 0.12 0.11 0.11 0.11 0.11 0.11 0.11 - 0.11Specific Electrical Resistance, microhm-cm at 70 ºF 70 77 81 85 80 75-85 75-85 85 90 978 94 99.1 102 100 105 112 116 - 988

Thermal Conductivity, Btu/hr/sq ft/ft/°F

At 212 ºF 15.0 12.6 12.6 8.5 8.3 8.2 8.2 8.2 7.9 8.2 8.2 7.5 7.5 7.0 7.0 7.2 7.2 - 8.2 At 1000 ºF 15.7 17.9 17.9 12.4 12.3 12.0 12.0 12.0 11.8 12.96 12.2 11.0 11.0 10.8 10.8 11.1 11.1 13.46

At 1400 ºF - - - 14.6 14.6 14.1 14.1 14.1 14.2 - 14.7 13.2 13.2 12.9 12.9 13.3 13.3 - At 1500 ºF - 20.3 20.3 - - - - - - 14.87 - - - - - - - 15.57

At 2000 ºF - 24.2 24.2 18.2 - 17.5 17.5 17.5 18.6 - 19.3 17.0 17.0 16.3 16.3 17.0 17.0 - Melting Point (approx), ºF 2750 2725 2700 2650 2550 2500 2500 2550 2550 2490 2600 2500 2450 2450 2450 2350 2350 - 2400Magnetic Permeability Ferro-

Magnetic Ferro-

Magnetic Ferro-

Magnetic 1.3-2.5 1.00 1.0-1.9 1.0-1.05 1.0-1.7 1.02 - 1.01 1.10 1.02-1.25 1.10-2.00 1.10-

2.00 16.0 2.0 - -

168- 212 ºF 61110 ºF 268- 930 ºF 71470 ºF 368-1470 ºF 8 75 ºF 468-1650 ºF aCalculated 568-1830 ºF

17

AERONAUTICAL The high temperatures encountered in aircraft power plants

and afterburners have been controlled by the use of heat-resistant alloy castings.

Typical Applications

Jet engine rotors Jet engine rings

Afterburner parts Gun blast tubes

CEMENT In kiln processes, heat, corrosion and abrasion are con-

stantly attacking operating equipment. High-alloy castings resist high temperatures, corrosive gases and abrasives and reduce breakage, shut-down time and rapid wear.


Burner nozzles Conveyors Cooler lifters Dampers Kiln chains

Kiln end rings Kiln feed chutes Kiln shell segments Slurry feed pipes

CONTINUOUS CAST CHAIN Alloy: HH (25Cr-12Ni) Weight: 50 Ib Use: Cement Kiln

GLASS AND ENAMELING In the glass, pottery and enameling industries, handling

equipment must have sufficient strength at elevated tempera-tures to resist bending and warpage. The alloys used must resist scaling or flaking to prevent contamination of the prod-uct. Some heat-resistant cast alloys have both these charac-teristics and they are used extensively.

LEHR ROLLS Alloy: HF (19Cr-9Ni) Weight: 1040 Ib Size: 8 in. O.D., 6 in. I.D., 168 in. long Use: Supports glass without bending at operating temperature of

1500 ºF.

Industrial Applicationsof Heat-Resistant Alloy Castings


Trays Molds Fixtures Hangers Burning tools

Brick supports Suspension bars Hearth plates Kilns and furnaces Lehr rolls

18

Glass and Enameling (Cont'd.)

ENAMELING FURNACE FLOOR IRONS Alloy: HT (35Ni-15Cr) Weight: 575 Ib (large casting) Use: Operates at 1800 ºF

HEAT TREATING

The advantages of high-alloy castings have been frequently demonstrated in heat-treating equipment. High temperatures, heavy loads, thermal shock and the continuous operation of heat-treating furnaces require the use of heat-resistant alloy

castings for long uninterrupted service and low maintenance and operating costs. The uses of high-alloy castings in heat-treating operations are extensive.

SHAFT FIXTURE ON TRAY Alloy: HU (39Ni-15Cr) Weight: 87 Ib Use: Carburizing furnace

MUFFLER ASSEMBLIES Alloy: HT (35Ni-15Cr) Size: Each casting 24 in. long, wall thickness ¼ in. Use: Handle hot gases (1750-1800 ºF) of glassmaking furnace.


Trays Boxes and baskets Retorts Fixtures Conveyor belts and chainsFurnace hearths Furnace hearth supports Roller rails Grates

Roller conveyors Screw conveyors Skid rails Hot fans Molten metal pots Furnace muffles Radiant tubes Dampers Heat exchangers

19

Heat Treating (Cont'd.)

GEAR FIXTURE ON TRAY Alloy: HU (39Ni-18Cr) Weight: 75 Ib Use: Carburizing furnace

TRAY WITH CRISS-CROSS FIXTURE Alloy: HU (39Ni-18Cr) Weight: 56 Ib Use: Carburizing furnace

RIVETLESS CHAIN Alloy: HW (60Ni-12Cr) Weight: 5 lb each Size: 5 in. x 6 in. x 1¾in. Use: Convey parts through hardening

furnace operating at 1650 ºF.

TRAY Alloy: HU (39Ni-18Cr) Weight: 40 lb Use: Roller rail furnace

ARTICULATED TRAY WITH TUBULAR FIXTURE Alloy: HX (66Ni-17Cr) Weight: 178 lb Use: Solution treat aircraft parts (water quenched).

20

SIDE HEARTH LINK BELT Alloy: HH (25Cr-12Ni) Weight: According to size Size: 3 in., 4 in., or 6 in. pitch Use: Convey parts through continuous furnaces operating at 1600 to 1800 ºF

TUBULAR BASE WITH GRIDS Alloy: HT (35Ni-17Cr) Weight: 1170 lb Use: Pit furnace base support

GRID WITH LIFTING LOOPS Alloy: HU (39Ni-18Cr) Weight: 265 lb Use: Pit furnace top support

TUBULAR GRID ROLLER TRAY Alloy: HT (35Ni-17Cr) Weight: 164 lb Use: Malleablizing furnace

21

PIT FIXTURE WITH SPACER GRIDS Alloy: HT (35Ni-17Cr) Weight: 1173 Ib Use: Carburizing furnace

PIT FIXTURE CAGE Alloy: HX (66Ni-17Cr) Weight: 930 Ib Use: Solution treat space parts.

TRAY WITH TWO CRISS-CROSS FIXTURES Alloy: HU (39Ni-18Cr) Weight: 115 Ib Use: Carburizing furnace

PIT FURNACE RING Alloy: HX (66Ni-17Cr) Weight: 849 Ib Use: Solution treat space parts (water quenched).

22

PETROLEUM, PETROCHEMICAL REFINING AND CHEMICALThe heat-resistant grades of high-alloy castings are used

extensively in the petroleum refining industry. High-pressure and high-temperature refining units depend on high-alloy sup-ports, tubes, headers and other castings which can withstand excessive heat and corrosion. Metal parts used in refineries and rectifying plants are subject to extreme temperatures, heavy loadings, and corrosive liquids and gases. Among heat-resistant alloy casting grades are those that assure protection from deterioration caused by heating and cooling cycling and resist corrosive media at temperatures up to 2000 ºF. HK-40 and IN-519 are used extensively for catalyst tubes in steam-hydrocarbon reforming furnaces. The chromium-nickel alloys, 50Cr-50Ni and IN-657, show excellent resistance to fuel oil ash attack and are used extensively in Europe to resist this material.

High-alloy castings serve many applications in the chemical equipment field where heat-resistant castings are permitting

high output operation under severe corrosive and temperature conditions.


Beams and channels Pumps Valves Pistons Retorts Roof tube hangers Dampers

Tube sheets Tubes Tube supports and wall tiesHeater tubes Fittings Burners and nozzles

FLANGES AND REDUCERSAlloy: HF with 5-15% ferrite (19Cr-9Ni) Weight: 1500 lb (flanges) Use: High temperature piping in

petrochemical plant.

U-BEND RETURN Alloy: HK-40 (25Cr-20Ni) Weight: 45 Ib Size: 4 in. O.D. x 10 in. center to center Use: Ethylene converter furnace

CAST WELDING WYE Alloy: HP (35Ni-26Cr) Weight: 74 lb Size: 14 in. long, 10 in. center to center Use: Pyrolysis furnace

23

VERTICAL TUBULAR BEAM WITH LOOSE ACCESSORIES Alloy: HK (25Cr-20Ni) Weight: 153 Ib Use: Petrochemical tube support

FURNACE TUBE ASSEMBLIES Alloy: HP (35Ni-26Cr) Weight: 500 lb per assembly Size: 3.75 in. O.D. x 3.12 in. I.D. x 20 ºFt long Use: Coil, radiant section, pyrolysis furnace

TUBE SUPPORT Alloy: HH (25Cr-12Ni) Weight: 15 Ib Use: Petrochemical industry

WELD ELBOW WITH TRUNNION PAD Alloy: HK-40 modified with Cb (25Cr-20Ni-Cb) Weight: 23 Ib Size: 4 in. O.D. x 3 in. ID Use: Ethylene converter furnace

24

TUBE SUPPORTS Alloy: HH (25Cr-12Ni) Weight: 6 Ib Use: Petrochemical industry

SIDE SUPPORTS AND TUBE SHEETS Alloy: HK (25Cr-20Ni) Weight: Sheets, 170 lb; supports, 407 lb

HORIZONTAL TUBULAR BEAM WITH ACCESSORIES Alloy: HK (25Cr-20Ni) Weight: 253 Ib Use: Petrochemical tube support

HORIZONTAL TUBULAR BEAM WITH ACCESSORIES Alloy: HK (25Cr-20Ni) Weight: 299 Ib Use: Petrochemical tube support

25

REDUCING ELBOW Alloy: HK-40 (25Cr-20Ni) Weight: 10 Ib Size: I.D. reduction 4½ in. to 1½ in. Use: Reformer tube assemblies

CENTRIFUGALLY-CASTFURNACE TUBE Alloy: HK-40 (25Cr-20Ni) Weight: 245 Ib Size: 4 in. O.D. x 3 in. I.D. x 156 in. long Use: Furnace tube section

BURNER DIFFUSER Alloy: HX (66Ni-17Cr) Weight: 27 Ib Use: Petrochemical industry


Tube supports Hanger bolts Brick and tile supports Dampers

Nozzles Beams Burner diffusers Valve bodies

POWER PLANTS

Because of the higher operating temperatures being used in superheater and boiler units, extensive use is being made of heat-resistant cast alloys. The proper use of high-alloy castings avoids costly shutdowns and reduces maintenance requirements

BURNER NOZZLESAlloy: HE (29Cr-9Ni) Weight: 10 to 15 lb each Use: Burners operating at temperatures up to 1800 ºF

26

STEEL MILL EQUIPMENT The advantages of heat-resistant alloy castings have been

demonstrated by the steel industry in many high-temperature applications. These alloys are capable of operation at high speeds, temperatures and loads and provide reliable opera-tion for long periods, thus reducing equipment upkeep and operating costs.

FURNACE DRUMAlloy: HK-40 (25Cr-20Ni) Weight: 10,000 Ib Size: 60 in. major O.D. Use: Turn-down roll in steel mill furnace for normalizing sheet.

GUIDESAlloy: HH (25Cr-20Ni) Weight: 2 and 14 Ib Use: Steel rod mill guides

REFRACTORY-LINED BLOWPIPES Alloy: HP (35Ni-26Cr) Weight: 600 Ib (pipe) Size: 10 in. O.D. barrel with 14 in. O.D. bell ends Use: Steel mill blast furnace

SMELTING AND REFINING EQUIPMENT Many years ago, this industry recognized the savings that

were possible if high-alloy castings were properly utilized. In the sintering and smelting of ores, high temperatures, acid gases and abrasion contribute to the destruction of furnace, hearth, kiln and sintering machine parts. Heat-resistant alloy castings reduce operating and maintenance costs by provid-ing durability and heat resistance.


Rabble arms Feed spouts

Plows Hearth plates

Rabbles Lute rings

Air arms Grate

Chains Seal plates

Dampers Furnace tubes

COOLER GRATES Alloy: HH (25Cr-12Ni) Weight: 20 to 40 Ib Use: Iron ore pelletizing and cement kiln

GRATE BARSAlloy: HH (25Cr-12Ni) Weight: 12 Ib Use: Iron ore sintering and pelletizing furnace


Baffles Furnace beams and rails Conveyor parts Furnace doors and frames Dampers

Retorts Radiant tubes Recuperators Skid rails Muffles

27

The corrosion-resistant casting alloys are those com-positions capable of performing satisfactorily in a large variety of corrosive environments. They are composed principally of nickel, chromium and iron; sometimes also containing other elements. Castings made of these al-loys offer two basic advantages:

1. Facility of the production of complex shapes at low cost.

2. Ease of securing rigidity and high strength-to-weight ratios.

Some typical alloy compositions are given in Table V, the room temperature mechanical properties in Table

VI, the physical properties in Table VII and the heat treating temperatures in Table VIII.

Commercial cast corrosion-resistant alloy can be identified by the designations of the Alloy Casting Insti-tute, now a division of the Steel Founders' Society of America, and the American Society for Testing and Materials.* Some of these materials are also listed in the Aerospace Material Specifications (AMS) of the Society of Automotive Engineers, the United States Govern-ment Specifications (MIL and QQ), the Society of Auto-motive Engineers Specifications and the Unified Num-bering System (UNS) developed by the Society of Auto-motive Engineers and the American Society for Testing and Materials.

TABLE V Compositions of Corrosion-Resistant Alloy Castings

CHEMICAL COMPOSITION, %

Alloy Casting Institute

Designation Alloy Type

ASTM (or other)

Specification

AISI (or other) Wrought

Comparative UNS No.

Ni Cr Mo Cu C Max

Mn Max

Si Max

Other

CA-15 12Cr A296, A487 410 J91150 1.0 11.5-14.0 0.5 – 0.15 1.00 1.50 Fe bal CA-40 12Cr A296 420 J91153 1.0 11.5-14.0 0.5 – 0.20-0.40 1.00 1.50 Fe bal CA-6NM 12Cr-4Ni A296,A487 – J91540 3.5-4.5 11.5-14.0 0.40-1.0 – 0.06 1.00 1.00 Fe bal CA-6N1 12Cr-7Ni A296 – – 6.0-8.0 10.5-12.5 – – 0.06 0.50 1.00 Fe bal CB-30 20Cr A296 442 J91803 2.0 18-22 – – 0.30 1.00 1.50 Fe bal CB-7Cu-1 17Cr-4Ni A747 17-4PH2 – 3.6-4.6 15.5-17.7 – 2.5-3.2 0.07 0.70 1.00 Cb 0.20-0.35; N 0.05

max; Fe bal CB-7Cu-2 15Cr-5Ni A747 15-5PH2 – 4.5-5.5 14.0-15.5 – 2.5-3.2 0.07 0.70 1.00 Cb 0.20-0.35: N 0.05

max; Fe bal CC-50 28Cr A296 446 J92615 4.0 26-30 – – 0.50 1.00 1.50 Fe bal CD-4MCu 26Cr-5Ni A296 – – 4.75-6.0 25-26.5 1.75-2.25 2.75-3.25 0.04 1.00 1.00 Fe bal CE-30 29Cr-9Ni A296 312 J93423 8-11 26-30 – – 0.30 1.50 2.00 Fe bal CF-3 19Cr-10Ni A296, A351 304L J92500 8-12 17-21 – – 0.03 1.50 2.00 Fe bal CF-8 19Cr-9Ni A296, A351 MIL-S-867 304 J92600 8-11 18-21 – – 0.08 1.50 2.00 Fe bal CF-20 19Cr-9Ni A296 302 J92602 8-11 18-21 – – 0.20 1.50 2.00 Fe bal CF-3M 19Cr-10Ni A296, A351 316L J92800 9-13 17-21 2.0-3.0 – 0.03 1.50 1.50 Fe bal CF-8M 19Cr-10Ni A296, A351 316 J92900 9-12 18-21 2.0-3.0 – 0.08 1.50 1.50 Fe bal CF-8C 19Cr-10Ni A296, A351 347 J92710 9-12 18-21 – – 0.08 1.50 2.00 Cb 8XC min, 1.0 max

or Cb-Ta 9XC min, 1.1 max; Fe bal

CF-16F 19Cr-10Ni A296 303 J92701 9-12 18-21 1.50 – 0.16 1.50 2.00 Se 0.20-0.35; Fe bal CG-8M 19Cr-10Ni A296 MIL-S-867 317 J93000 9-13 18-21 3.0-4.0 – 0.08 1.50 1.50 Fe bal CH-20 25Cr-12Ni A296, A351 309 J93402 12-15 22-26 – – 0.20 1.50 2.00 Fe bal CK-20 25Cr-20Ni A296, A351 AMS 5365 310 J94202 19-22 23-27 – – 0.20 1.50 2.00 Fe bal CN-7M 20Cr-29Ni A296, A351 – J95150 27.5-30.5 19-22 2.0-3.0 3.0-4.0 0.07 1.50 1.50 Fe bal IN-8623 – – – – 23-25 20-22 4.5-5.5 – 0.07 1.50 1.00 Fe bal CW-12M1 – A296, A494 – – bal 15.5-20.0 16.0-20.0 –

0.12 1.00 1.50 W 5.25 max; V 0.40

max; Fe 7.50 max CY-401 Ni-Cr-Fe A296, A494 INCONEL4 alloy 600 – bal 14.0-17.0 – – 0.40 1.50 3.00 Fe 11.0 max Alloy 6253 – – – – bal 20-23 8.0-10.0 – 0.06 1.00 0.75 Cb 3.15-4.50;

Fe 5.0 max CZ-1001 Ni A296, A494 Nickel 200 – bal – – 1.25 1.0 1.50 2.00 Fe 3.0 max M-351 Ni-Cu A296, A494 MONEL4 QQ-N-288 alloy 400 – bal – – 26.0-33.0 0.35 1.50 2.00 Fe 3.50 max N-12M1 Ni-Mo A296, A494 – – bal 1.00 26.0-33.0 – 0.12 1.00 1.00 V 0.60 max; Fe 6.0 max

– Ni-Si – – – bal 1.00 – 2.4 – 0.50-1.25 8.5-10.0 W 1 max 1ASTM designation 3INCO designation2Trademark of Armco Steel Corporation 4Trademark of the INCO family of companies

Note: ASTM A.296 will be replaced by two new standards, A 743 and A 744 in the 1978 Annual Book of ASTM Standards. A 743 will cover the martensitic and ferritic types and A 744 the austenitic types. A 296 will appear in the 1978 Book of Standards but will be dropped in the 1979 Book.

*See ASTM Specification A 296

Part ll Corrosion-Resistant Alloy Castings

28

TABLE VI Room Temperature Mechanical Properties of Corrosion-Resistant Alloy Castings

PROPERTY CA-15CA-40 CA- 6NM

CA-6N CB-30

CB- 7Cu-1

CB- 7Cu-2 CC-50

CD- 4MCu CE-30 CF-3 CF-8 CF-20 CF-3M CF-8M F-8C

CF-16F CG-8M CH-20 CK-20 CN-7M

IN- 862

CW- 12M CY-40

Alloy625

CZ- 100 M-35 N-12M

2001 2201 1205 1406 957 17012a 17012a 70 8a 1089 9510 7711 7711 7711 8011 8011 7711 7711 8211 8811 7611 6911 60 726 65-9010 706 50-6510 65-8510 726 1352 1502 15012b 15012b 95 8b 9711

Tensile Strength, ksi 1153 1403 14512c 14512c 1004 1104 13512d 13512d 12512e 12512e Yield 1501 1651 1005 1356 607 14512a 14512a 65 8a 829 4510 3611 3711 3611 3811 4211 3811 4011 4411 5011 3811 3211 25 466 32-5010,13 406 15-3010,13 30-4010,13 466 Strength 1152 1252 14012b 14012b 60 8b 6311 (0.2% offset) 1003 1133 11512c 11512C ksi 754 674 11012d 11012d 9712e 9712e Elongation 71 11 245 156 157 512a 512a 2 8a 259 1510 6011 5511 5011 5511 5011 3911 5211 4511 3811 3711 4811 40 46 20-1010 206 30-1510 50-2510 66 in 2 in., % 172 102 912b 912b 15 8b 1811 223 143 912c 912c 304 184 912d 912d 1012e 1012e

Brinell 3901 4701 2695 – 1957 37512a 37512a 212 8a 2539 19010 14011 14011 16311 15011 156–17011 14911 15011 17611 19011 14411 13011 130 – 150–20010 – 90–13010

125–17010 –

Hardness 2602 3102 31112b 31112b 193 8b 19011 2253 2673 27712c 27712c 1854 2124 26912d 26912d 26912e 26912e Modulus of Elasticity, ksi x 103

29 29 29 29.5 29 28.5 – 29 29 25 28 28 28 28 28 28 28 28 28 29 24 – – 23 – 21.5 23 –

1 Air cooled from 1800 ºF. Tempered at 600 ºF. 2 Air cooled from 1800 ºF. Tempered at 1100 ºF. 3 Air cooled from 1800 ºF. Tempered at 1200 ºF. 4 Air cooled from 1800 ºF. Tempered at 1400 ºF. 5 Air cooled from above 1750 ºF. Tempered at 1100-1150 ºF. 6 Minimum 7 Annealed at 1450 ºF. F.C. to 1000 ºF, then air cooled. 8 a Under 1% Ni

b Over 2% Ni with 0.15 Nitrogen, minimum

9Solution annealed at 2050 ºF. Water quenched from 1900 ºF. 10As cast 11Water quenched from 2000-2050 ºF. 12a PH heat treatment H900, minimum values. b PH heat treatment H1025, minimum values. c PH heat treatment H1075, minimum values. d PH heat treatment H1100, minimum values. e PH heat treatment H1150, minimum values. 13 0.5% extension

TABLE VII Physical Properties of Corrosion-Resistant Alloy Castings

PROPERTY CA-15 CA-40 CA- 6NM CA-6N CB-30

CB- 7Cu-1

CB- 7Cu-2 CC-50

CD- 4MCu CE-30 CF-3 CF-8

CF-20

CF-3M

CF-8M

CF-8C

CF-16F

CG-8M

CH-20

CK-20

CN- 7M

IN- 862

CW-12M CY-40

Alloy-625

CZ-100 M-35

N- 12M

Density, Ib/cu in. 0.275 0.275 0.278 0.280 0.272 0.280 0.269a 0.272 0.280 0.277 0.280 0.280 0.280 0.280 0.280 0.280 0.280 0.280 0.279 0.280 0.289 0.292a0.336a 0.300 0.305 0.301 0.312 0.334a

Specific Heat, Btu db/°F at 70

ºF 0.11 0.11 0.11 - 0.11 0.11 - 0.12 0.11 0.14 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.11 - - 0.11 0.10 0.13 0.13 -

Mean Coefficient of Linear Thermal Expansion, in./in./°F x 106

70 - 212 ºF 5.5 5.5 6.0 5.7 6.0 - 5.9 6.3 - 9.0 9.0 9.6 8.9 8.9 9.3 9.0 8.9 8.6 8.3 8.6 - - - 7.1 - - - 70 - 1000 ºF 6.4 6.4 7.0 6.21 6.5 6.4 6.9 9.6 10.0 10.0 10.4 9.7 9.7 10.3 9.9 9.7 9.5 9.4 9.7 - 7.8 - 70 - 1200 ºF - - - - - 7.0 9.9 - 10.2 - - - - - - - - - - 8.2 - 70 - 1300 ºF 6.7 6.7 - 6.7 - - - - - - - - - - - - - - - - 70 - 1400 ºF - - - - - - 10.2 - - - - - - - - - - 8.9 8.5 8.9 70 - 1600 ºF - - - - - - 10.5 - - - - - - - - - - - - 8.8 -

Specific Electrical

Resistance microhm cm at 70 ºF 78 76 78 - 76 77 - 77 75 85 76.2 76.2 77.9 82 82 71 72 82 84 90 89.6 - - 116 129 21 53 - Thermal Conductivity, Btu/hr/sq ft/ft/°F

at 212 ºF 14.5 14.5 14.5 - 12.8 9.9 - 12.6 8.8 8.5 9.2 9.2 9.2 9.4 9.4 9.3 9.4 9.4 8.2 7.9 12.1 - - 8.7 6.3 34 15.5 - at 1000 ºF 16.7 16.7 16.7 14.5 17.9 13.4 12.4 12.1 12.1 12.1 12.3 12.3 12.8 12.3 12.3 12.0 11.8 - 10.0

Melting Point _ _ (approx), ºF 2750 2725 2750 - 2725 2750 - 2725 2700 2650 2650 2600 2575 2600 2550 2600 2550 2550 2600 2600 2650 - - 2600 2460 2600 2400 - Magnetic Permeability

Ferro- Magnetic

Ferro- Magnetic

Ferro- Magnetic –

Ferro Magnetic

Ferro- Magnetic

- Ferro- Magnetic

Ferro-Magnetic

over1.5

1.20-3.00

1.00-1.30 1.01

1.50-3.00

1.50-250

1.20-1.80

1.00-2.00

1.50-3.00 1.71 1.02

1.01- 1.10

1.00

170-600 ºF 2Data from wrought equivalent aCalculated

29

The Alloy Casting Institute and ASTM designations use "C" to indicate alloys used primarily for their corrosion-resistant properties. The second letter indi-cates the nominal nickel content, increasing from A to Z.

The S.A.E. specifications use the nearest wrought composition (AISI type number) and prefix it with the number 60 ºFor corrosion-resistant castings; for exam-ple, 60304 is equivalent to CF-8. In the Unified Num-

bering System, Jxxxx number series has been assigned to cast steels.

The chemical compositions of the corrosion-resistant casting alloys are not the same as those of the wrought alloys. Therefore, Table V lists only the nearest AISI or other wrought comparative. Alloy Casting Institute des-ignations or their equivalent should always be used to identify castings.

1Reheat to 1500 ºF, air cool 2Aging Temperature 3Precipitation hardened

Temperature Condition 900 ºF H 900 925 ºF H 925 1025 ºF H1025 1075 ºF H1075 1100 ºF H1100 1150 ºF H1150

*Held 3 hours, slowly cooled to 1400-1750 ºF, cooled in water, oil or air.

EFFECT OF CONSTITUENTS

Chromium

A chromium content of at least 11.5% is required to provide surface passivity under oxidizing conditions and to form an inert adherent surface film rich in chromium oxide which is highly resistant to attack. A higher chro-mium content broadens the range of oxidizing condi-tions under which passivity is maintained. The chro-mium content of corrosion-resistant castings ranges from 12 to 28% in the ACI alloys.

Nickel

The addition of nickel supplements the passivating effect of chromium under oxidizing conditions and also increases the resistance of the alloys to attack under reducing conditions. Nickel in sufficient concentration results in a desirable austenitic structure and preserves this structure through the many heat treatments to which castings may be subjected during production and subsequent fabrication. In the higher nickel alloys, nickel provides increased resistance to most reducing

TABLE VIII Heat Treatment of Corrosion-Resistant Alloy Castings

Alloy Casting Institute Designation Anneal at Harden at Temper at Quench

CA-15 1450-1650 ºF 1800-1850 ºF 600 ºF, max or 1100-1500 ºF - CA-40 1450-1650 ºF 1800-1850 ºF 600 ºF, max or 1100-1500 ºF - CA-6NM 1450-1500 ºF 1900-1950 ºF 600 ºF, max or 1100-1500 ºF - CA-6N 1900 ºF1 - 800 ºF2 air cool CB-30 1450 ºF, min - - air cool CB-7Cu-1 1925 ºF - 900-1150 ºF3 air cool CB-7Cu-2 1925 ºF - 900-1150 ºF3 air cool CC-50 1450 ºF, min - - air or furnace cool CD-4MCu 2050 ºF, min4 - - - CE-30 2000-2050 ºF - - water, oil or air CF-3 1900-2050 ºF - - water, oil or air CF-8 1900-2050 ºF - - water, oil or air CF-20 2000-2100 ºF - - water, oil or air CF-3M 1900-2050 ºF - - water, oil or air CF-8M 1950-2100 ºF - - water, oil or air CF-8C 1950-2050 ºF - - water, oil or air CF-16F 1950-2050 ºF - - water, oil or air CG-8M 1900-2050 ºF - - water, oil or air CH-20 2000-2100 ºF - - water, oil or air CK-20 2000-2150 ºF - - water, oil or air CN-7M 2050 ºF, min - - water, oil or air IN-862 2150 ºF - - water CW-12M 2200-2250 ºF - - water CY-40 - - - - Alloy 625 2150 ºF - - water Cz-100 - - - - M-35 - - - - N-12M 2100-2150 ºF - - water

30

environments. It also provides improved resistance to those chemical compounds to which nickel is particu-larly resistant. These are typified by strong alkalies and halogen compounds. In corrosion-resistant castings, the nickel content ranges from 1 to 96%.

Molybdenum Molybdenum has specific beneficial effects in improv-

ing resistance to sulfuric, phosphoric and hydrochloric acids. It also reduces the tendencies toward pitting in sea water and other chloride solutions. In the ACI alloys, the molybdenum content ranges from none to 30%.

Other Elements Although chromium, nickel and molybdenum have

the greatest influence on the properties of corrosion-resistant castings, other alloying elements also have their effects.

Carbon can have a detrimental effect on corrosion resistance by combining with chromium to form a car-bide. This undesirable effect can be eliminated by:

(a) Holding the carbon content below 0.03%.

(b) Introducing columbium or titanium to form car-bides of these elements instead of the harmful chromium carbide.

(c) Heating the alloy to a temperature sufficiently high to dissolve the carbon and cooling rapidly enough to hold the carbon in solution.

Columbium is added as a stabilizer to prevent precipi-tation of chromium carbides.

Copper acts in the same manner as molybdenum to improve resistance to sulfuric and phosphoric acids.

Selenium in small quantities improves machinability but it reduces corrosion resistance somewhat.

Silicon also contributes to resistance to reducing acids such as sulfuric, but impairs resistance to nitric acid. The silicon content of cast corrosion-resistant alloys is higher than that of the wrought alloys because this element contributes the fluidity required to obtain satisfactory casting characteristics. However, silicon is a promoter of ferrite formation and, as a consequence, tends to cause the formation of small amounts of ferrite in the austenitic matrix. As one result, silicon increases the resistance of cast corrosion-resistant alloys to chloride ion stress-corrosion cracking.

CORROSIVE ATTACK

Corrosion is a complex phenomenon in which numer-ous variables influence not only the severity but also the type of attack. Therefore, it is not possible to make specific recommendations for alloy selection in a gen-eral publication. Certain limitations on the use of corrosion-resistant alloy castings and suggestions for counteracting them are discussed below. Table IX is included to serve as a guide in selecting candidate alloys for an environment. Where corrosion data on cast

alloys were sparse, data on the wrought counterpart were included on the assumption that corrosion rates for both cast and wrought alloys would be similar.

Pitting Corrosion Stainless steels are subject to localized loss of pas-

sivity and subsequent pitting by the action of chloride ions which penetrate the passive surface films. The incidence of such pitting is determined by the competi-tion between the chloride ions which destroy passivity and dissolved oxygen or other oxidizing substances which passivate the surface. It is affected also by the composition of the alloy and the exposure conditions. Favorable factors are the presence of molybdenum and a high nickel content represented, for example, by the 51% Ni-17% Mo-16.5% Cr compositions which is usu-ally resistant to pitting by chloride solutions even under adverse conditions. Favorable environmental factors are a plentiful supply of oxygen or other oxidizing agent or, conversely, no oxygen at all, a high alkalinity and low temperature, a medium to high flow rate and freedom from deposits. The most unfavorable condition is repre-sented by exposure beneath deposits to a stagnant solution containing some dissolved oxygen. Turbulence associated with high velocity flow is generally beneficial.

Sensitization When an austenitic stainless steel containing more

than 0.03% carbon, which is not stabilized by the pres-ence of columbium or titanium, is heated in the 900-1400 ºF range, chromium carbide will precipitate at the grain boundaries. The localized depletion of chromium may make the alloy susceptible to intergranular attack in environments in which it ordinarily shows good resistance. Sensitization can usually be avoided by keeping the carbon content at 0.03% or less, by adding small quantities of columbium or titanium, or by heating to 2000 ºF for one hour per inch of thickness followed by quenching in water.

Magnetic Properties The Alloy Casting Institute grades containing up to

4% nickel are all magnetic, as is the CE-30 grade. AIl other grades fall within the austenitic alloy class, because of their compositions, and are substantially non- magnetic. A small amount of magnetic ferrite is desirable to facilitate weld repair although this ferrite may not be detected by a magnet. Occasionally, when the chromium is on the high side of the specification and the nickel is on the low side, an unbalanced condition will develop in austenitic alloys that results in the formation of a two-phase alloy composed of austenite and ferrite The presence of ferrite in the structure will cause the alloy to be slightly magnetic. This two-phase structure will have corrosion resistance in practically all environments equivalent to that of the single-phase austenitic structure. An exception is in ammonium carbamate solutions such as are encountered in urea production.

31

Stress-Corrosion Cracking Under the combined effects of tensile stress and cor-

rosion by specific environments (most commonly con-centrated chlorides), certain stainless steel composi-tions are subject to stress-corrosion cracking. Nickel has the greatest effect on resistance to this form of attack. Resistance to such cracking is improved by in-creasing the nickel content above the 8% level of the common CF-8 grade.

Although cast austenitic stainless steels are often considered to be similar to their wrought counterparts, there is a difference. There is usually a small amount of

ferrite present in austenitic stainless steel castings, in contrast with the single-phase austenitic structure of the wrought alloys. The presence of ferrite in the castings is desirable to facilitate weld repair but also increases resistance to stress-corrosion cracking. There have been only a few stress-corrosion cracking failures with cast stainless steels in comparison with the approxi-mately equivalent wrought compositions. The principal reasons for this resistance are apparently (a) lower stresses, (b) silicon added for fluidity is also beneficial from the standpoint of stress-corrosion cracking and (c) sand castings are usually tumbled or sandblasted to remove molding sand and scale which probably tends to put the surface in compression.

GROUPS OF CORROSION-RESISTANT ALLOY CASTINGS

The iron-base corrosion resistant alloys can be clas-sifed according to composition and metallurgical struc-ture into four broad groups:

1. Martensitic Alloys: CA-15, CA-40, CA-6NM, CA-6N

2. Ferritic and Duplex Alloys: CB-30, CC-50, CD-4MCu

3. Austenitic Alloys: CE-30, CF types, CG-8M, CH-20, CK-20, CN-7M, CN-7MS, IN-862

4. Precipitation Hardenable Alloys: CB-7Cu-1, Cb-7Cu-2

In addition, nickel-base corrosion-resistant alloys in-clude nickel, high nickel-copper alloys, high nickel-chromium alloys and other proprietary alloys.

MARTENSITIC ALLOYS

CA-15 (12Cr-1Ni) This alloy contains the minimum content required to

attain surface passivity under oxidizing conditions. It has good resistance to many mildly corrosive environ-ments that are oxidizing in character. It also has good resistance to velocity effects in solutions for which it is suitable. The alloy is used widely for seats and discs in valves in steam service and for parts of turbines ex-posed to high velocity steam

CA-40 (12Cr-1Ni) This is the cutlery type of stainless steel which, by

virtue of its higher carbon content, can be hardened to a greater depth than type CA-15. It has good corrosion resistance to many environments, is tough and has good resistance to abrasion. It is used for chipper blades, cutter blades, cylinder liners, grinding plugs, shredder sleeves and steam turbine parts.

CA-6NM (12Cr-4Ni) This is an iron-chromium-nickel-molybdenum alloy

that is hardenable by heat treatment. In general corro-sion resistance, it is similar to CA-15 and has been widely substituted for CA-15 because of easier process-ing through the foundry cleaning room. Among uses are compressor wheels, diaphragms, hydraulic turbine

parts, impulse wheels and pumps and valves for boiler feedwater service.

CA-6N (12Cr-7Ni) This is a higher nickel content modification of CA-15

which has an excellent combination of strength, tough-ness and weldability. It has moderately good corrosion resistance.

FERRITIC AND DUPLEX ALLOYS

CB-30 (20Cr-2Ni) Because of its higher chromium content, this alloy has

better resistance to corrosion in many oxidizing environ-ments than the CA alloys. The addition of 2% nickel enhances corrosion resistance and increases tough-ness. It also has good abrasion resistance. Uses in-clude pump parts, turbine parts and valve trim.

CC-50 (28Cr-4Ni) Alloys containing about 28% chromium and up to 4%

nickel are resistant to a number of highly oxidizing me-dia such as hot nitric acid. They are also used in han-dling corrosives such as acid mine waters which are oxidizing and may be mildly abrasive. Among applica-tions are cylinder liners, digester parts, pump casings and impellers.

CD-4MCu (26Cr-5Ni-3Cu-2Mo) As cast, this alloy has a duplex ferrite and austenite

structure. Because of its low carbon content, there are only small amounts of chromium carbides distributed throughout the matrix, but for maximum corrosion resis-tance, these carbides must be dissolved by suitable heat treatment. Although the alloy can be precipitation hardened, the ACI recommends that this alloy be used only in the solution annealed condition. It is highly resis-tant to attack by some concentrations of sulfuric and hydrochloric acids and is exceptionally resistant to stress-corrosion cracking in chloride-containing solu-tions or vapors. It has also shown outstanding resis-tance to such mixtures as nitric-adipic acid slurries and wet process phosphoric acid slurries. Uses include compressor cylinders, pump impellers, digester valves and feed screws.

32

AUSTENITIC ALLOYS

CE-30 (29Cr-9Ni) This alloy also is resistant to a number of highly

oxidizing corrosives and is particularly used for pumps, valves and fittings handling sulfite liquors in the paper industry and some acid slurries in the metallurgical in-dustries. Because of its high chromium content, the alloy can be made with a higher carbon content than the CF type alloy without suffering the injurious effects of carbide precipitation. For the same reason, it may be used in place of the CF alloys where they must be welded without subsequent heat treatment. While often used in the as-cast condition, ductility and corrosion resistance of the CE alloy may be improved somewhat by quenching from about 2000 ºF. Uses include digester necks and fittings, circulating systems, fractionating towers, pump bodies and casings.

CF Alloys (19Cr-9Ni)

The austenitic alloys containing about 19% chro-mium, 9% nickel and less than 0.20% carbon constitute by far the most widely used group of corrosion-resistant stainless alloys. These alloys are used for handling a wide variety of corrosive solutions in the chemical, tex-tile, petroleum, pharmaceutical, food and numerous other process industries. In the chemical industry, they are particularly useful in handling oxidizing solutions such as nitric acid and peroxides and mixtures of acids such as sulfuric and phosphoric with oxidizing salts such as ferric, cupric, mercuric and chromic salts. These stainless alloys are resistant to most organic acids and compounds as encountered in the food, dairy and pharmaceutical industries. They also are resistant to most waters including mine, river, boiler and tap waters. They are resistant to sea water under the high velocity conditions associated with pumping but are subject to severe pitting attack in stagnant or slow mov-ing sea water.

The limitation of the CF alloys is that most halogen acids and halogen acid salts tend to destroy their sur-face passivity. Thus, they are subject to considerable attack in such media as hydrochloric acid, acid chloride salts, wet chlorinated hydrocarbons, wet chlorine and strong hypochlorites.

For best resistance to corrosion, this alloy is produced in the low carbon CF-3 and CF-8 grades and should be solution annealed to prevent intergranular attack in severely corrosive media. Heat treated CF-3 castings can be field welded or hot formed without subsequent re-solution annealing, a major advantage in many appli-cations.

Columbium (niobium) or columbium plus tantalum are sometimes added to produce carbide-stabilized CF-8C alloy which, after heat treating, can be field welded or used at elevated temperatures without the precipitation of chromium carbides and resultant susceptibility to intergranular attack of chromium depleted regions.

The addition of molybdenum as in grades CF-3M and CF-8M considerably increases the resistance of the CF-alloys to such corrosive media as sulfuric, sulfurous

and phosphoric acids and to certain hot organic acids such as formic, acetic and lactic acids. Molybdenum also improves resistance to pitting in chloride salt solu-tions and sea water.

Grade CF-16F is similar to grades CF-8 and CF-20 to which small amounts of selenium have been added to improve the machinability. The corrosion resistance of this alloy is somewhat inferior to that of the CF-20 alloy but is adequate for many purposes.

Controlled Ferrite Types

The strength of the CF alloys cannot be improved by heat treatment but these alloys can be strengthened by increasing the ferrite phase at the expense of the aus-tenite phase in these duplex microstructures. This fact has led to the introduction of controlled ferrite types, designated with an "A" suffix in some CF alloys, i.e., CF-3A and CF-8A, for applications where higher strength is desired than is obtainable in the CF-3 and CF-8 types. Minimum tensile strengths for these con-trolled ferrite types are 7 to 10 ksi higher than for the regular types. The increased ferrite content generally improves the resistance of the alloy to stress-corrosion cracking in addition to increasing the strength. Because of the thermal instability of the higher ferrite microstruc-ture, however, the controlled ferrite types are not con-sidered suitable for service at temperatures above 650 ºF (CF-3A) or 800 ºF (CF-8A).

CG-8M (19Cr-8Ni)

The high molybdenum content of this alloy (3-4%) gives it improved resistance to hot sulfurous and or-ganic acids and to dilute sulfuric acid. It also has great resistance to pitting. Uses include dyeing equipment, flow meter components, pump parts and propellers.

CH-20 (25Cr-12Ni)

With a carbon content of less than 0.20%, this alloy is similar in corrosion resistance to the CE-30 composi-tion. It is used for specialized applications in the chemi-cal and paper industries. Uses include digester fittings, roasting equipment, valves and pump parts.

CK-20 (25Cr-20Ni)

This alloy is somewhat similar to the CE and CH types but has higher nickel content. It is sometimes made with a columbium, or columbium plus tantalum addition, to minimize the effect of carbide precipitation. It is used in the pulp and paper industry to handle sulfite solutions. Uses include digesters, filter press plates and frames, mixing kettles and return bends.

CN-7M (29Ni-20Cr)

This designation covers a group of complex nickel chromium-copper-molybdenum alloys containing more nickel than chromium. The increased nickel content together with the addition of copper and molybdenum give the alloy especially good resistance to sulfuric acid and to many reducing chemicals. It has good resistance

33

to dilute hydrochloric acid and to hot chloride salt solu-tions. The alloy also has excellent resistance to nitric and phosphoric acids. Uses include filter parts, heat exchanger parts, mixer components, pickling hooks and racks, steam jets and ventilating fans; pumps and valves represent a major part of CN-7M applications.

CN-7MS (24Ni-19Cr-3Mo-2Cu) The CN-7MS modification of CN-7M was developed

for improved castability and weldability. Its corrosion resistance is substantially equivalent to the CN-7M alloy.

IN-862 (24Ni-21Cr-5Mo)

This alloy was developed as an alternative to CN-7M for service in sea water. With its increased molybdenum content, it has better resistance to pitting and crevice corrosion than CN-7M but its corrosion resistance in sulfuric acid environments is lower. It has excellent casting and welding properties, thus giving it advan-tages in production and repair compared with CN-7M.

PRECIPITATION HARDENABLE ALLOYS

CB-7Cu-1 (16Cr-4Ni-3Cu) This complex chromium-nickel-copper alloy can be

hardened by a precipitation heat treatment after solution annealing. It is not intended for use in the solution annealed condition. The alloy can be used in service requiring corrosion resistance and high strength at tem-peratures up to 600 ºF. In the precipitation hardened condition, its corrosion resistance approaches that of the CF-8 alloy under certain conditions.

CB-7Cu-2 (15Cr-5Ni-3Cu) This complex chromium-nickel-copper alloy can be

hardened by a precipitation hardening heat treatment after solution annealing. It is not intended for use in the solution annealed condition. It has a superior combina-tion of strength, toughness and weldability with moder-ately good corrosion resistance.

NICKEL-BASE ALLOYS

CZ-100 (95Ni min) Cast nickel is outstanding for maintaining the purity of

a wide range of drugs, foods and chemicals. It is widely used for the manufacture of caustics and for handling caustics in processes where low iron and copper content in the equipment is important.

M-35 (63Ni-30Cu) This alloy shows good resistance to attack in reducing

environments. It is widely used in handling sulfuric, hydrochloric and organic acids in the marine, petro-leum, chemical, power, sanitation, plastics, steel and food processing industries.

CY-40 (74Ni-15Cr) This nickel-base alloy has a superior combination of

corrosion resistance under a wide variety of conditions plus high levels of strength, ductility and weldability. It protects product purity much as nickel does, but is more

resistant to oxidizing conditions. It is stronger and har-der than nickel, and as tough. Industries in which it is used are: dairy, chemical, pharmaceutical, nuclear, pe-troleum and food processing. Its corrosion resistance to nitric acid, fatty acids, ammonium hydroxide solutions and oxidizing conditions in general is superior to nickel. This alloy is particularly useful in handling corrosive vapors above 1470 ºF.

Alloy 625 (60Ni-21Cr-9Mo) This high nickel-chromium-molybdenum alloy, like its

wrought counterpart INCONEL* alloy 625, has excellent corrosion resistance, especially in sea water, and is highly resistant to chloride stress-corrosion cracking. It has superior corrosion resistance in oxidizing atmos-pheres and to sulfur, and organic and inorganic com-pounds over a wide temperature range. Cast Alloy 625 has high levels of fatigue and creep strength, above those of CY-40. Sand-cast Alloy 625 can be air melted and poured, processed through the cleaning room in the as-cast condition, and can be welded using SMA (coated electrode) or GMA (gas metal arc) processes without preheat or postweld heat treatments.

CW-12M (55Ni-18Cr-18Mo) This complex nickel-chromium-molybdenum alloy

sometimes contains 5% tungsten and minor amounts of other elements. It has outstanding resistance to such highly corrosive media as wet chlorine, strong hypo-chlorite solutions, ferric chloride and cupric chloride and is often applied in the handling of such chemicals. It also has good resistance to boiling concentrated or-ganic acids such as acetic, formic, lactic and fatty acids. Maximum corrosion resistance is obtained by quench-ing the cast alloy from an annealing temperature of 2200-2250 ºF.

N-12M (63Ni-30Mo) This alloy was developed particularly for resistance

to corrosion by hot concentrated hydrochloric acid solu-tions and wet hydrogen chloride. It is also resistant to hot concentrated solutions of pure phosphoric acid and to hot dilute sulfuric acid. The alloy is most resistant under reducing conditions and is not considered suitable for handling oxidizing acids or solutions containing oxidizing salts. Maximum corrosion resistance is ob-tained by quenching the cast alloy from an annealing temperature of 2100-2150 ºF.

Nickel-Silicon Alloy (82Ni-10Si)

This nickel-silicon alloy which sometimes also con-tains 3% copper has exceptional resistance to all con-centrations of sulfuric acid up to the boiling point; conse-quently it is used in the concentration of sulfuric acid. It is also resistant to many other chemicals including phos-phoric, formic and acetic acids under reducing condi-tions but is not resistant to strong oxidizing acids. Be-cause of its high hardness, this alloy is used extensively to resist wear, abrasion and galling where corrosion may

*Trademark of the INCO family of companies

34

TABLE IX Corrosion Data

Corrosive Medium CA-15 CA-40 CB-30 CC-50 CD-4MCu

CE-30CF-3 CF-8

CF-20

CF-3M CF-8M CF-8C CF-16F

Acetic Acid 5% 4 4 3 3 1 2 2 1 2 2 10% 4 4 4 4 1 2 2 1 2 2 15% 4 4 4 4 1 2 2 1 2 2 20% 5 5 4 4 1 2 2 1 2 3 30% 5 5 5 5 1 2 2 1 2 3 40% 5 5 5 5 1 2 2 1 2 3 50% 5 5 5 5 1 3 3 1 3 3 60% 5 5 5 5 2 3 3 2 3 3 80% 5 5 5 5 2 3 3 2 3 3 99.9% 5 5 5 5 2 3 3 2 3 3

Acetic Anhydride 90% 5 5 5 5 2 3 3 2 3 3

Acetic Acid Vapors 30% 5 5 5 5 2 3 3 2 3 3 100% 5 5 5 5 3 4 4 3 4 4

Aluminum Acetate 4 4 4 4 1 2 2 1 2 2 Aluminum Chloride 5 5 5 5 4 5 5 5 5 5 Aluminum Hydroxide 4* 4* 4* 4* 3 4* 4* 3 4* 4* Aluminum Sulfate

5% 4 4 4 4 1 2 2 1 2 2 10% 5 5 5 5 1 3 3 1 3 3 Saturated 5 5 5 5 1 5 5 1 5 5

Alum (Aluminum Potassium Sulfate) 10% 5 5 5 5 1 3 3 1 3 3 Saturated 5 5 5 5 2 4 4 2 4 4

Ammonium Bicarbonate 3 3 2 2 1 1 1 1 1 2 Ammonium Carbonate 3 3 2 2 1 1 1 1 1 2 Ammonium Chloride

1% 2* 2* 2* 2* 1* 1* 1* 1 1* 1* 10% 3* 3* 3* 3* 2* 2* 2* 2* 2* 2* 20% 5 5 5 5 2* 4* 4* 3* 4* 4* 50% 5 5 5 5 3* 4* 4* 3* 4* 4*

Ammonium Nitrate 2 2 2 2 1 1 1 1 1 1 Ammonium Sulfate

1% 3 3 3 3 1 1 1 1 1 1 5% 3 3 3 3 1 2 2 1 2 2 10% 4 4 4 4 1 2 2 1 2 2 Saturated 5 5 5 5 2 3 3 2 3 3

Bromine Liquid (Dry) 5 5 5 5 4 5 5 4 5 5

Bromine Liquid (H2O Saturated) 5 5 5 5 5 5 5 5 5 5

Bromine Water (Dilute) 5 5 5 5 4 5 5 4 5 5 Calcium Chloride 5 5 5 5 4 5 5 5 5 5 Calcium Hypochlorite 5 5 5 5 5 5 5 5 5 5 Chlorine Gas (Moist) 5 5 5 5 5 5 5 5 5 5 Copper Sulfate 4 4 3 3 1 2 2 1 2 2 Ethylene Glycol 3 3 3 3 1 2 2 1 2 2 Fatty Acids 300 ºF 300 ºF 300 ºF 300 ºF 600 ºF 400 ºF 400 ºF 600 ºF 400 ºF 400 ºFFerric Chloride 5 5 5 5 5 5 5 5 5 5 Ferric Sulfate 4 4 4 4 2 3 3 2 3 3 Ferrous Sulfate 4 4 4 4 1 2 2 1 2 2

LEGEND 1. Good resistance to boiling. 4. Good resistance to 70 ºF. 2. Good resistance to 160 ºF. 5. Not recommended. 3. Good resistance to 120 ºF. *Subject to pitting. **Dilute concentrations.

35


Corrosive Medium CA-15 CA-40 CB-30 CC-50 CD-4MCu CE-30CF-3 CF-8

CF-20

CF-3M CF-8M CF-8C CF-16F

Fluosilicic Acid 5 5 5 5 4 5 5 4 5 5 Formic Acid

5% 4 4 4 4 2 2 2 1 2 2 10% 4 4 4 4 2 2 2 1 2 2 50% 4 4 4 4 3 3 3 1 3 3 100% 5 5 5 5 3 3 3 2 3 3

Hydrochloric Acid 5 5 5 5 5 5 5 5 5 5 Hydrobromic Acid 5 5 5 5 5 5 5 5 5 5 Hydrofluoric Acid 5 5 5 5 5 5 5 5 5 5 Hydrogen Peroxide 3 3 3 3 2 2 2 2 2 2 Lactic Acid

5% 3 3 3 3 1 2 2 1 2 2 10% 5 5 5 5 2 3 3 2 3 3 100% 5 5 5 5 2 3 3 2 3 3

Magnesium Chloride 5 5 5 5 4* 5 5 5 5 5 Magnesium Sulfate 5 5 3 3 2 2 2 1 2 2 Nickel Chloride 5 5 5 5 4* 4* 4* 4* 4* 4* Nickel Nitrate 3 3 2 2 2 2 2 2 2 2 Nickel Sulfate 5 5 5 5 1 3 3 2 3 3 Nitric Acid

5% 3 3 2 2 1 1 1 1 1 1 20% 3 3 2 2 1 1 1 1 1 1 40% 4 4 3 3 1 1 1 1 1 1 50% 4 4 3 3 1 1 1 1 1 1 65% 4 4 3 3 1 2 2 3 2 2 100% 5 5 4 4 4 4 4 4 4 4

Oxalic Acid 5% 4 4 3 3 1 2 2 1 2 3 10% 5 5 4 4 2 3 3 2 3 3 25% 5 5 4 4 2 3 3 2 3 4 50% 5 5 5 5 2 4 4 3 4 5

Phosphoric Acid (Pure) 5% 3 3 3 3 1 1 1 1 1 1 10% 3 3 3 3 1 1 1 1 1 1 25% 5 5 4 4 1 2 2 1 2 2 50% 5 5 4 4 1 2 2 1 2 2 85% 5 5 4 4 2 3 3 2 3 3

Potassium Sulfate 4 4 3 3 1 3 3 2 3 3 Sodium Carbonate 4 4 3 3 1 2 2 1 2 2 Sodium Chloride 5 5 4* 4* 2* 3* 3* 2* 3* 3* Sodium Hydroxide

< 20% 4 4 4 4 1 1 1 1 1 1 20-30% 4 4 4 4 2 2 2 2 2 2 30-50% 5 5 5 5 2 2 2 2 2 2 50-70% 5 5 5 5 5 5 5 5 5 5 70-80% 5 5 5 5 5 5 5 5 5 5

Sulfuric Acid 5-10% 5 5 5 5 2 4 4 3 4 4 10-20% 5 5 5 5 2 5 5 3 5 5 20-40% 5 5 5 5 3 5 5 5 5 5 40-60% 5 5 5 5 4 5 5 5 5 5 60-75% 5 5 5 5 4 5 5 5 5 5 75-85% 5 5 5 5 3 5 5 5 5 5 85-90% 5 5 5 5 2 4 4 3 4 4 90-100% 4 4 4 4 2 3 3 2 3 3

Zinc Chloride 5 5 5 5 3* 5 5 3* 5 5 Zinc Sulfate 5 5 5 5 1 4 4 2 4 4

(Continued on pages 36 and 37)

NOTE: It is not the purpose of this table to make specific recommendations. It should be used simply as a guide to indicate the most suitable candidate alloys. The effects of contamination, velocity, aeration, etc., will all tend to alter the rating of an alloy exposed to a corrosive environment.

36

TABLE IX

Corrosion Data

Corrosive Medium CH-20 CK-20 CN-7M N-12M CW-12MAlloy 625

Ni-Si Alloy CZ-100 M-35 CY-40

Acetic Acid 5% 2 2 1 1 1 1 1 4 3 1 10% 2 2 1 1 1 1 1 3 3 1 15% 2 2 1 1 1 1 1 3 3 2 20% 2 2 1 1 1 1 1 3 3 2 30% 2 2 1 1 1 1 1 3 3 2 40% 2 2 1 1 1 1 1 3 3 2 50% 2 2 1 1 1 1 1 3 3 2 60% 3 3 1 1 1 1 1 3 3 2 80% 3 3 1 1 1 1 1 3 3 2 99.9% 3 3 1 1 1 1 1 3 3 2

Acetic Anhydride 90% 3 3 1 1 1 1 1 3 3 2

Acetic Acid Vapors 30% 3 3 1 1 1 1 1 3 3 2 100% 4 4 1 1 1 1 1 3 3 2

Aluminum Acetate 2 2 1 1 1 1 1 3 3 2 Aluminum Chloride 5 5 4 1 3 4 2 2 2 2 Aluminum Hydroxide 4* 4* 2 1 1 2 1 2 2 2 Aluminum Sulfate

59% 2 2 1 1 1 1 1 3 3 3 10% 3 2 1 1 1 1 1 3 3 3 Saturated 4 4 1 1 1 1 1 5 5 3

Alum (Aluminum Potassium Sulfate) 10% 3 2 1 1 1 1 1 3 3 3 Saturated 3 3 1 1 1 1 3 5 5 4

Ammonium Bicarbonate 1 1 1 1 1 1 1 2 2 2 Ammonium Carbonate 1 1 1 1 1 1 1 2 2 2 Ammonium Chloride

1% 1* 1* 1* 1 1 1* 1 1 1 1 10% 2* 2* 2* 1 1 1* 1 1 1 2* 20% 4* 4* 2* 2 1 1* 2 1 1 2 50% 4* 4* 2* 2 1 2* 2 1 1 2*

Ammonium Nitrate 1 1 1 2 1 1 2 5 5 1 Ammonium Sulfate

1% 1 1 1 1 1 1 1 3 3 3 5% 2 2 1 1 1 1 1 3 3 3 10% 2 2 1 1 1 1 1 3 3 3 Saturated 3 3 1 1 1 1 1 3 3 3

Bromine Liquid (Dry) 5 5 3 3 2 3 3 1 1 1

Bromine Liquid (H2O Saturated) 5 5 4 3 2 3 3 3 3 3

Bromine Water (Dilute) 5 5 3 2 2 3 2 5 5 5 Calcium Chloride 5 5 4 3 1 3 3 2 2 2 Calcium Hypochlorite 5 5 5 5 3 4 5 5 5 5 Chlorine Gas (Moist) 5 5 4 3 1 4 3 5 5 5 Copper Sulfate 1 1 1 4 1 1 4 4 4 2 Ethylene Glycol 2 2 1 1 1 1 1 2 2 1 Fatty Acids 400 ºF 400 ºF 600 ºF+ 600 ºF+ 600 ºF+ 600 ºF 400 ºF 400 ºF 400 ºF 600 ºF Ferric Chloride 5 5 5 5 2 4 5 5 5 5 Ferric Sulfate 3 3 2 5 2 2 5 5 5 3 Ferrous Sulfate 2 2 1 2 1 1 2 3 3 3

LEGEND

1. Good resistance to boiling. 4. Good resistance to 70 ºF. 2. Good resistance to 160 ºF. 5. Not recommended. 3. Good resistance to 120 ºF. *Subject to pitting. **Dilute concentrations.

37


Corrosive Medium CH-20 CK-20 CN-7M N-12M CW-12MAlloy 625

Ni-Si Alloy CZ-100 M-35 CY-40

Fluosilicic Acid 5 5 3 3 2 2 3 4 1 4 Formic Acid

5% 2 2 1 2 1 1 2 2 1 2 10% 2 2 1 2 1 1 2 2 1 2 50% 3 3 1 3 1 1 3 2 1 2 100% 3 3 1 3 1 1 3 2 1 2

Hydrochloric Acid 5 5 5 2 3 4 5 3** 3** 4**Hydrobromic Acid 5 5 5 2 3 3 5 5** 5 5 Hydrofluoric Acid 5 5 4 4 3 4 4 4 1 4 Hydrogen Peroxide 2 2 2 5 3 3 5 3 4 2 Lactic Acid

5% 2 2 1 3 1 1 3 3 2 2 10% 3 3 1 4 1 1 4 3 2 2 100% 3 3 1 4 2 2 4 3 2 2

Magnesium Chloride 5 5 4* 1 1 1* 1 1 1 2* Magnesium Sulfate 2 2 1 1 1 1 1 2 2 2 Nickel Chloride 4* 4* 3* 1 2 3* 3 2 2 3* Nickel Nitrate 2 2 2 4 2 2 5 5 5 3 Nickel Sulfate 3 3 1 2 1 2 2 2* 2* 2 Nitric Acid

5% 1 1 1 5 1 2 5 5 5 3 20% 1 1 1 5 2 3 5 5 5 3 40% 1 1 1 5 3 3 5 5 5 3 50% 1 1 1 5 3 3 5 5 5 3 65% 2 2 2 5 4 4 5 5 5 3 100% 4 4 3 5 5 5 5 5 5 3

Oxalic Acid 5% 2 2 1 1 1 1 1 3 2 3 10% 3 3 1 1 1 1 3 3 2 3 25% 3 3 1 2 1 1 3 3 2 3 50% 4 4 1 3 1 1 4 3 2 3

Phosphoric Acid (Pure) 5% 1 1 1 1 1 1 1 4 1 3 10% 1 1 1 1 1 1 1 4 1 3 25°% 1 1 1 1 1 1 1 4 2 3 50% 2 2 1 1 1 1 1 4 2 3 85% 3 3 2 1 2 2 2 4 3 3

Potassium Sulfate 3 3 1 1 1 1 1 3 1 2 Sodium Carbonate 2 2 1 1 1 1 1 1 1 1 Sodium Chloride 3* 3* 1* 1 1 1 1 2 1 2* Sodium Hydroxide

<20% 1 1 1 1 1 1 1 1 1 1 20-30% 2 2 1 1 1 1 1 1 1 1 30-50°% 2 2 1 1 1 1 1 1 1 1 50-70% 5 5 270 ºF 4 4 2 1 1 1 1 70-80% 5 5 270 ºF 4 4 2 1 1 1 1

Sulfuric Acid 5-10% 4 4 2 1 1 1 1 4 2 3 10-20% 5 5 2 1 1 2 1 4 2 3 20-40% 5 5 2 1 2 3 1 4 4 3 40-60% 5 5 3 1 2 4 1 5 4 4 60-75% 5 5 3 2 2 4 2 5 5 5 75-85% 5 5 3 2 2 4 2 5 5 5 85-90% 4 4 2 2 2 3 2 5 5 3 90-100% 3 3 225 ºF 250 ºF 2 2 2 4 4 3

Zinc Chloride 5 5 2* 1 2* 2* 1 2 1 2* Zinc Sulfate 4 4 1 1 1 1 1 2 1 3

NOTE: It s not the purpose of this table to make specific recommendations. It should be used simply as a guide to indicate the most suitable candidate alloys The effects of contamination, velocity, aeration, etc., will all tend to alter the rating of an alloy exposed to a corrosive environment.

38

AERONAUTICAL Although the greatest use for high alloys in this industry

is for engine parts required to withstand high temperatures, there are applications for the corrosion-resistant grades in components that must resist both corrosive and erosive effects to insure dependable operation.


Fuel jets Fuel valves Engine supports

BALL VALVE Alloy: CF-8 (19Cr-9Ni) Use: Cryogenic ball valve for service on advanced rocket engine.

CONTROL VALVE Alloy: CB-30 modified Use: Aircraft fuel control valve subject to high rate fuel impingement on 2000 mph aircraft.

ARCHITECTURAL

The cast chromium-nickel alloys are used as ornaments and other components in the architectural treatment of buildings, bridges, etc. Where these will be exposed to a marine environment, the molybdenum-containing austenitic grades have the most satisfactory resistance to corrosion.


Ornaments Hand rail fittings

Fire wall fittings Grilles

Industrial Applicationsof Corrosion-Resistant Alloy Castings

39

CHEMICAL AND PETROLEUM Chemical

The corrosion-resistant alloys have their widest application in the chemical industry. Their function is two-fold: they pro-vide good equipment life and prevent product contamination. Many chemical operations would not be economically feasible if it were not for the corrosion and abrasion-resistant properties of these alloys.


Grinders Mixers Pumps Valves

Nozzles Vessels Piping and fittings Conveyors

Petroleum Cast corrosion-resistant alloys of all types are used exten-

sively in the petroleum industry to withstand the corrosive effects of moist sulfur and carbon dioxide-bearing gases, sour crudes, sulfuric acid and caustic treating equipment, phos-phoric acid, salt water and the many forms of organic acids produced as by-products during the refining operations.


Valves Pumps Heater tubes

Pipe fittings Nozzles

PROCESS PIPING Alloy: CF-3M (19Cr-10Ni-2Mo) Weight: 1400 Ib Size: 16 in. O.D. x ¾ in. wall; flange 26 in. O.D. Use: Acetic acid processing

CENTRIFUGAL PUMP CASING AND COVER Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 4000 Ib each pump Use: Pump to circulate 5500 gpm of highly corrosive chemicals with low specific gravity.

CENTRIFUGALLY-CAST FLANGE Alloy: CH-20 modified with free ferrite controlled at 5-15% (25Cr-12Ni) Weight: 150 Ib Size: 4 in. 2500 Ib welding neck flange @ 14 in. flange O.D. x 3 in. thick x 4½

in. neck O.D. x 7¾ in. O.A.L. Use: Hydrocracker refinery unit

PRESSURE VESSEL Alloy: CK-20 (25Cr-20Ni) Weight: 8,900 Ib Use: Dissolver vessel in chemical processing plant.

40

BUTTERFLY VALVE–AUTOMATIC CONTROL Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 600 Ib Size: 24 in. Use: Chemical service

PUMP COMPONENTS Alloy: CF-8 (19Cr-9Ni) and CF-8M (19Cr-9Ni-2Mo) Parts: Housings, gears, impellers Use: Pumps in a variety of applications primarily in

the Chemical Processing Industry. All parts are investment castings

PUMP Alloy: CG-8M (Modified)–wetted parts Size: 16 in. Use: Flash cooler service in

phosphoric acid plant.

BUTTERFLY VALVE-AUTOMATIC, ON-OFF Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: Body and disc 300 Ib Size: 12 in. Use: Chemical service

GATE VALVE Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: Body casting, 1603 lb;

bonnet casting, 414 Ib Use: Wedge gate valve for chemical

plant service.

41

PROCESS INDUSTRIES EQUIPMENT

Food Processing The corrosion-resistant stainless steels are widely used in

all types of food handling equipment. Their good resistance to both corrosion and abrasion avoids the hazard of contamina-tion with metal compounds that might be toxic or might lead to food spoilage.

Metal Mining and Refining The austenitic stainless steels have good resistance

to all mine waters which contain sulfur compounds. The CF-8M alloy is usually reliable for most of these conditions.

In the sulfuric acid leaching of copper ores, the CN-7M alloy is used in pumps and valves required to handle the 66° Bé sulfuric acid solution. The copper-containing solution accumu-lated after leaching is resisted satisfactorily by the CF-8M alloy.

The CN-7M alloy is also widely used in the sulfuric acid treatment of phosphate ore for the production of phosphoric acid.

Pharmaceutical

The CF alloys (19Cr-9Ni) are widely used in the pharma-ceutical industry and in the fine chemical industry in corrosive as well as in relatively non-corrosive environments for main-taining purity and color of the products. Stainless steels are used in processing Vitamin C, acid solutions containing chlo-roform, ammonium sulfate, sodium sulfite and to resist organic acids from protein extraction and biological mediums.

Plating

The austenitic stainless steels are used in the electroplating industry for equipment to handle alkaline cyanide copper plating baths, sulfuric acid copper plating baths and some chromic acid plating baths. They are employed in pumps and valves in equipment used for the storage and handling of 66° Bé sulfuric acid. The stainless steels are not suitable for handling nickel chloride and other type plating baths. Tests should be con-ducted in solutions of this type to determine the suitability of alloys such as N-12M and CW-12M.

The austenitic stainless steels are used in equipment for handling the nitric-phosphoric bright-dip solution for alumi-num.

Pulp and Paper The severely corrosive conditions developed in both

the sulfite and the sulfate treating of wood require use of corrosion-resistant alloys for good service life and to avoid contamination by corrosion products. In the sulfite process, alloys having good resistance to acid environments are required while in the sulfate process alloys are required that have good resistance to caustic environments. Frequently, an alloy will be found that has satisfactory resistance to conditions encountered in both operations.

Many of the corrosion-resistant alloys have excellent resistance to erosive effects. This property is exploited in early grinding steps as well as in subsequent steps employed in processing the wood pulp.


Mixers Grinders Valves Pumps Agitators

Nozzles Disintegrators Screw spindles Screens


Valves Pumps

Pipe fittings Filters


Pumps Valves

Agitators Nozzles


Valves Pumps

Filters Fittings


Grinders Digester blow valves Stock line valves Stock lines and fittings White liquor equipment Green liquor equipment

Black liquor equipment Causticizing equipment Bleaching equipment Sulfuric and sulfurous acid

equipment Chlorine dioxide Sulfur dioxide

42

CENTRIFUGAL PUMP Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: Upper half 1175 lb; lower half 3000 lb Size: 57½ in high x 645/8 in. wide x 58½ in. deep Use: Pump for handling 14,800 gpm of caustic, corrosive paper stock ("white water").

VERTICAL PUMP Alloy: CF-8M (19Cr-9Ni-2Mo)–wetted parts Size: 24 in. Use: Liquid end of pump handling 20,000 gpm acid contaminated water.

CENTRIFUGE BOWL Alloy: CG-8M (19Cr-10Ni-3Mo) Weight: 1679 Ib Size: 28 in. O.D., 78 in. long Use: Centrifuges in municipal

sewage treatment plant.

TURBINE PUMP Alloy: CF-8M (19Cr-9Ni 2Mo)

–wetted parts Use: Dewatering service in gold

mine.

43

PUMP Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 450 Ib Size: 6 in. x 8 in.–1800 rpm Use: Sulfuric acid leaching of copper silicate ores at ambient

temperature. Sulfuric acid strength 1-2%.

DIGESTER SCREENS–PIPE FITTINGS Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: various–screen segments 100 Ib each Size: 6 in. pipe size at digester fitting Use: Screens separate pulp from liquor inside digester. Complex fittings

used at bottom of digester between it and blow pit. Liquor is ammonium sulfite (acid base).

SUCTION ROLL SHELLS (Suspended Castings) (Casting being bored) Alloy: CA-15 (12Cr) Alloy: CF-8M (19Cr-10Ni-2Mo) Weight: 97,200 lb Weight: 64,600 lb Use: Both used in wet end of paper machine to resist corrosion by white water while

aiding in drying paper.

SINGLE-STAGE CENTRIFUGAL PUMP Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 450 Ib Size: 8 in. x 10 in.–1800 rpm Use: Pumping silicate-sulfuric acid liquor in copper leaching

operation.

44

CENTRIFUGAL PUMP Alloy: CF-8M (Modified) Weight: Top casing, 1600 lb; lowercasing, 2380 lb Use: Handling acidic river water in steel plant–after 22 years, pump showed no sign of corrosion.

SINGLE STAGE CENTRIFUGAL PUMP Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 600 lb Size: 6 in. x 8 in–1800 rpm Use: Stock pump in pulp mill based on ammonium sulfite process–acid-base sulfite liquor is present.

MARINE

Although CF-type alloy castings have to be used selectively in the marine field because of their susceptibility to pitting corrosion, they have applications where, because of velocity conditions, this form of deterioration cannot develop. The chromium-nickel type (CF-8) steels have been used successfully for propellers on tugs and other types of work-boats that are in relatively constant service.

The CF-3M, CF-8M and CN-7M alloys are frequently used for components in salt water pumps and valves. These alloys have also been used successfully in equipment which is exposed to a marine atmosphere.

PROPELLER Alloy: CF-3 (19Cr-9Ni) Weight: 22,660 Ib Size: 15 ft O.D. Use: Workboat


Ship propellers Salt water pumps

Salt water valves Some marine hardware

45

POWER–NUCLEAR AND CONVENTIONAL

Nuclear Energy In this field, heat and corrosion-resistant alloys are used

in both statically and centrifugally cast forms.

Rigid specifications may require tensile property tests, hydrostatic tests, radiographic and dye penetrant examina-tions, depending upon the particular application.

CENTRIFUGALLY-CAST PIPE Alloy: CF-8A (19Cr-9Ni) Weight: 11,500 Ib (front piece) Size: 32 in. O.D., 184 in. long (front piece) Use: Nuclear reactor coolant loop pipe for pressurized water

reactor. Meets requirements of ASME Sec. III. Power Plants The use of chromium-nickel stainless steels for compo-

nents in power plant equipment has increased the ability of this industry to meet the ever increasing demand for more industrial power. These alloys have made it possible for power plant engineers to design equipment for operation at increased pressures and temperatures.

In nuclear power plants, the chromium-nickel stainless steels are used to avoid contamination of the coolants by metallic corrosion products that would become radioactive.

Hydraulics In the hydraulics field, the good resistance to

abrasion and cavitation of the chromium-nickel alloys is of more significance than their corrosion resistance. This property makes it possible to design smaller diameter equipment that will convey large volumes at higher velocity than it would be possible with other alloys that do not have this inherent characteristic.

CENTRIFUGALLY-CAST TUBE Alloy: CF-8 (19Cr-9Ni) Weight: 410 Ib Size: 8.2 in. O.D. x 5 in. I.D. x 56 in. long Use: Nuclear control rod drive latch housing.

CENTRIFUGALLY-CAST FLANGES Alloy: CF-8M with controlled ferrite (19Cr-10Ni-2Mo) Weight: 1500 Ib Size: up to 24 in. pipe size Use: Nuclear piping flowmeter flanges


Valves Pump impellers Pump casings

Control mechanisms Reactor components


Feed water heating equipment Boiler water deaerator heaters Valve components (feed water, steam, condensate, fuel oil) Pump components (feed water, condensate, fuel oil)


Pumps Valves Torque tubes

Nozzles Piping and fittings

46

VALVE BODY AND BONNET CASTINGS Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: Body casting, 1565 lb; bonnet casting, 740 Ib Use: Castings meet Nuclear Class II, used in valves for nuclear power

plant.

BUTTERFLY VALVE BODIES Alloy: CF-8M (19Cr-10Ni-2Mo) Weight: 300 Ib Size: 16 in. Use: Nuclear service–must meet ASME Class II requirements.

FRANCIS TYPE RUNNER Alloy: CF-20 (19Cr-9Ni) Weight: Range from 460 to 3030 Ib Size: 325/8 in. dia Use: For hydraulic turbine installations

in the power industry.

CENTRIFUGALLY-CAST BEARINGS Alloy: CF-3A (19Cr-9Ni) Weight: 800-900 Ib Size: 331/2 in. flange O.D. x 28 in. barrel

O.D. x 255/8 in. I.D. x 17 in. long Use: Hydrostatic bearings for nuclear

recirculating pumps.

47

FLOWMETER NOZZLES Alloy: CF-8M with controlled ferrite (19Cr-10Ni-2Mo) Weight: 975 Ib Size: 243/8 in. flange x 16 in. barrel O.D. x 1¼ in. wall

x 341/8 in. long Use: Venturi-style flowmeter bodies for use inside main water

recirculating in nuclear power plants.

CHECK VALVE Alloy: CF-8 (19Cr-9Ni) Weight: 450 Ib Size: 6 in. pipe size Use: Nuclear water service handling

demineralized water in the primary loop of a pressurized light water reactor.

STEAM TURBINE CASING Alloy: CK-20 (25Cr-20Ni) Weight: 9000 Ib Use: High temperature, high pressure steam

service.

CONTROL VALVE, AUTOMATIC CONTROL Alloy: CF-8 (19Cr-9Ni) Weight: 250 Ib Size: 6 in. pipe size Use: Nuclear service, light water reactor,

PWR primary loop, by-pass.

48

BUTTERFLY VALVE DISC Alloy: CF-3M (19Cr-9Ni-2Mo) Weight 160 lb Size: 20 in. dia Use: Control valve handling raw fresh water from California project to filtering

plant.

BAILEY CONTROL VALVE Alloy: CF-3M (19Cr-9Ni-2Mo) Weight: 5200lb Size: 32 in. dia (port size) Use: Potable water service, Metropolitan Water District of Southern California.

MULTISTAGE WATERFLOOD PUMP CASING Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 4200 lb Size: 4 in. x 6 in -3600 rpm Use: Waterflood Huntington Beach, California. Aminol-treated sea water, de-aerated, inhibited, biocides added.

CENTRIFUGAL PUMP IMPELLER Alloy: CF-8M (19Cr-9Ni-2Mo) Height: 36,000 lb Size: 144 in. dia Use: Handling freshwater containing silt, on Central Valley California

water project. Replaced bronze which suffered cavitation and erosion corrosion.

HORIZONTALLY SPLIT, 5 STAGE, HIGH PRESSURE PUMP Alloy: CF-8M (19Cr-9Ni-2Mo) Weight: 1050 Ib (part shown) Size: 4 in. x 6 in. -3600, rpm Use: Treated sea water–oil field water flood service.

49

Casting is a fabricating step and by its nature is the quickest method of converting an alloy into a nearly finished product. The elimination of intermediate steps between the molten metal stage and the shaped part provides important economic advantages to the casting process.

Many castings can be used directly after cleaning and cutting off the gates and risers but some require machin-ing to finished dimensions or welding into assemblies. This section presents information on the machining and welding practices used on heat and corrosion-resistant castings.

MACHINING

High-alloy castings are more difficult to machine than carbon steel because of the characteristics built into them for heat and corrosion-resistant service. With proper tools and coolants, however, all necessary ma-chining can be performed under conditions of compara-tively slow speeds and moderate feeds.

High speed steel and cemented carbide tools are used for machining the high alloy castings. Cutting speeds and feeds for high speed steel tools are shown in Table X for heat-resistant alloys and in Table XI for corrosion-resistant alloys. With carbide tools, about two to three times these speeds should be used. The tool should not be permitted to dwell in the cut as work hardening of the material will result. Machines should be powerful and rigid and tool mountings stiff.

Cutting lubricants are essential for all machining op-erations on these castings. For best results, a continu-ous and abundant supply of cutting fluid should be fed to the tool and thereby act also as a coolant. All lubricants should be removed completely from the machined parts that are to be subjected to high temperatures, either during subsequent fabrication or in service. For high speed steel tools, sulfurized cutting oils are the pre-ferred cutting lubricants. A lubricant of soluble oil and water is used with cemented carbide tools.

Single point tool grind angles for high speed steel are shown in Figure 6.

TABLE X Machining and Welding of Heat-Resistant Alloy Castings

HA HC HD HE HF HH HI HK HL HN HP HT HU HW HX

MACHINING Rough Turn Speed, sfm 40-50 40-50 40-50 30-40 25-35 25-35 25-35 25-35 30-40 35-45 35-45 40-45 40-45 40-45 40-45 Feed, ipr .010-.030 .025-.035 .025-.035 .020-.025 .015-.020 .015-.020 .015-.020 .020-.025 .020-.025 .020-.025 .020-.025 .025-.035 .025-.035 .025-.035 .025-.035

Finish Turning Speed, sfm 80-100 80-100 80-100 60-80 50-70 50-70 50-70 50-70 60-80 70-90 70-90 80-90 80-90 80-90 80-90 Feed, ipr .005-.010 .010-.015 .010-.015 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .010-.015 .010-.015 .010-.015

Drilling Speed, sfm 35-70 40-60 40-60 30-60 20-40 20-40 20-40 20-40 30-60 40-60 40-60 40-60 40-60 40-60 40-60 Feed, ipr 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

Tapping Speed, sfm 10-25 10-25 10-25 10-25 10-20 10-20 10-20 10-20 10-25 5-15 5-15 5-15 5-15 5-15 5-15 Remarks 15 17 15 17 15 17 17 16 17 16 17 16 17 16 17 17 16 17 – 16 17 16 17 16 17 16 17

WELDING Electrode Type

E505-18 E446-15 E446-15 E312-15 E308-15 E309-15 E310-15HC E310-15 E310-15HC E330-15 E310-15 E330-15 E330-15 (also 18Cr-38Ni Bare)

ENiCr-1 orENiCrFe-

1

ENiCrFe-1

Oxy-acetylene Rod Type 410 Bare 446 Bare 327 Bare 312 Bare 308 Bare 309 Bare 309 Bare 310 Bare 310 Bare 330 Bare – 330 Bare 330 Bare Inconel Inconel Oxy-acetylene Flux None None None None None None None None None None – None None Stainless StainlessOxy-acetylene Flame Character1

– – – – – S S M M – V V – –

Preheat and Interpass Temperature, F

450-550 60-100 Not. Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req.

Post Heat Treatment, F 2 1550 A. C. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req.Annealing Treatment, F 16255 As-Cast As-Cast As-Cast As-Cast3 As-Cast4 As-Cast As-Cast As-Cast As-Cast As-Cast As-Cast4 As-Cast4 As-Cast As-Cast

Notes for Table X with Table XI on page 50.

Part III Fabrication Data For Heat and Corrosion-Resistant Alloys

50

TABLE XI Machining and Welding of Corrosion-Resistant Alloy Castings

CA-15 CA-40

CA- 6NM CB-30 CC-50

CD-4MCu CE-30 CF-3 CF-8 CF-20 CF-3M CF-8M CF-8C CF-16F CG-8M CH-20 CK-20 CN-7M

MACHINING Rough Turn

Speed, sfm 40-50 25-35 40-50 40-50 40-50 40-50 30-40 25-35 25-35 25-35 25-35 25-35 30-40 45-55 25-35 25-35 25-35 45-55 Feed, ipr 010-.030 .030-.040 .010-.030 .020-.030 .025-.035 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025 .020-.025

Finish Turning Speed, sfm 80-100 50-70 80-100 80-100 80-100 80-100 60-80 50-70 50-70 50-70 50-70 50-70 60-80 90-110 50-70 50-70 50-70 90-110 Feed, ipr .003-.010 .015-.020 .005-.010 .010-.015 .010-.015 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010 .005-.010

Drilling Speed, sfm 35-70 30-60 20-50 30-60 40-60 20-40 30-60 20-40 20-40 20-40 20-50 20-50 30-60 30-80 20-50 20-50 20-40 30-60 Feed, ipr 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

Tapping Speed, sfm 10-25 10-20 10-20 10-25 10-25 10-20 10-25 10-20 10-20 10-20 10-20 10-20 10-25 15-30 10-20 10-20 10-20 10-25 Remarks 12 13 – 14 14 – 15 15 15 15 15 15 15 – 15 15 15 –

WELDING

Electrode Type E410-15 E410-15 – E442-15 E446-15 – E312-15 E308L-15 E308-15 E308-15 E316L-15 E316-15 E347-15 E308-15 E317-15 E309-15 E310-5 E320-15

Oxy-acetylene Rod Type

410 Bare 420 Bare – – – – – – – – – – – – – – – – Preheat and Interpass Temperature, ºF 400-600 400-600 500-600 600-800 350-400 Not. Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. Not Req. 400-500

Post Heat Treatment, ºF

1125- 1400 A.C.

1125- 1400 A.C.

1100- 1150 A.C.

1450- 1500 A.C.

1650 A. C. 2050 1950- 20507

Not Req. 1950- 20507

2000- 21007

Not Req. 1950- 21007

1950- 20507

2000- 21007

1950- 2050

2000- 21007

2WQ- 21507

1950 20507

Annealing Treatment, ºF 1550-

1650 F.C. 1550-

1650 F.C. 1450-

1500 F.C.

1450- 1500 F.C.

8

1450- 1500 F.C.

or A.C.

2050 F.C.to 1750-

1900 A.C.

9 1950- 2050

9 9 1950- 2150

9 9 9 – 9 9 9

Heat Treatment for Increasing Strength – – – 11 11 – 11 11 11 11 11 11 11 11 11 11 11 11 Hardening Temp., ºF 1800-

1850 1800- 1850

1900- 1950

– – – – – – – – – – – – – – –

Quenching Medium oil oil oil – – – – – – – – – – – – – – – or air or air or air

Tempering Temp., ºF 600 max 10

600 max 10

600 max 10

– – – – – – – – – – – – – – –

Notes for Tables X and XI

1V – very rich in acetylene; excess acetylene feather should project 1" beyond tip of inner core.

M – medium rich in acetylene; excess acetylene feather should project ½" beyond tip of inner core.

S – slightly rich in acetylene; excess acetylene feather should project ¼" beyond tip of inner core.

2 Heat to original draw temperature, hold sufficiently long to insure uniform heating throughout section, then air cool.

3 When castings are repeatedly heated and cooled in service, properties may be improved by heating at 1900 ºF for six hours, then furnace cooling.

4 When castings are repeatedly heated and cooled in service, properties may be improved by heating at 1900 ºF for twelve hours, then furnace cooling.

5 For improved strength, castings are normalized by heating to 1825 ºF, air cooling to below 1300 ºF, followed by tempering at 1250 ºF.

6 Drilling feeds: Drill Diameter Feed, ipr

Under 1/ 8 “ 001-.002 1/ 8 - ¼ 002-.004

¼ - ½ .004-.007

½ - 1 .007-.015 Over 1 015-.025

7 This post-weld heat treatment is to restore maximum corrosion resistance. Quench should be in water, oil or air according to section size, geometry and cooling rate that will hold as great a portion of the carbides in solution as possible.

8 Furnace cool to 1000 ºF, then air cool. 9 Same as post-heat treatment. 10 Avoid tempering around 900 ºF. Lower strengths than obtained with 600 ºF

max temper may be achieved by tempering in 1100-1500 ºF range. 11 This alloy normally supplied in the annealed condition. 12 Cuts best when hardened to 225 Brinell. 13 Chips are stringy. 14 Chips are short and brittle. 15 Use chip curler. 16 Use chip curler and breakers. 17 Chips are tough and stringy.

Not Req. –usually not required. A.C. –air cool F.C. –furnace cool

51

WELDING All of the common welding methods can be used on high-alloy castings. Information on pre-heat and post-heat treatments are given for the heat-resistant alloys in Table X and for corrosion-resistant alloys in Table XI. The metal-arc process is used in most cases, especially for the corrosion-resistant alloys, while oxy-acetylene welding is usually limited to the heat-resistant types. Oxy-acetylene welding is not normally used for corrosion-resistant castings because carbon pick-up is possible if the flame is not correctly adjusted. Carbon pick-up would decrease the corrosion-resistance of the chromium-nickel alloys. In the relatively tougher heat-resistant alloys, this limitation does not exist and oxy-acetylene welding can be employed. Inert-gas welding with tungsten or consumable electrodes is common in the repair welding of investment castings. Submerged arc welding is confined mainly to fabrication of corrosion-resistant alloys. Flash welding is utilized in special applications, such as the joining of tubular sections.

1. Welding Nickel-Chromium and Chromium-Nickel Groups of Both Heat and Corrosion-Resistant Grades.

Alloy castings of the nickel-chromium-iron and chromium-nickel-iron groups can be welded satisfacto-rily and the resultant joints will have the same mechani-cal and physical properties as the base metal. These alloys have better weldability than the straight chro-mium alloys. Preheating is seldom required, but post-weld heat treatments are employed with the corrosion-resistant types to restore uniform corrosion resistance.

The thermal conductivity of these alloys is about one-third that of carbon steel and the thermal expansion coefficient is about 50% greater. This low conductivity results in the retention of local heat for longer times and the high coefficient of expansion means that higher residual stresses and more distortion can be anticipa-ted.

A. Arc Welding – The electrical resistance of nickel-chromium and chromium-nickel castings is about six times that of carbon steel, and the melting point of the alloys is approximately 100 ºF lower. This combination of greater resistance and lower melting point permits these alloys to be arc welded using lower currents than those required for welding carbon steels. Particular care must be exercised with the corrosion-resistant types to have the welding groove well cleaned and free of grease or dirt, for any contamination of the weld might result in carbon pick-up. When welding heat-resistant alloys of the nickel-chromium group, the work must be kept clean of lubricants and marking crayons that contain sulfur or lead; otherwise cracking may result. Weaving of the bead should be avoided because a large puddle pro-motes weld cracking unless bead width is limited to 3 times the electrode diameter.

Welding Current – Reverse polarity D.C. is most commonly used for welding the nickel-chromium and chromium-nickel alloys. Table XII lists suggested elec-trical settings and electrode sizes for these alloys of different thicknesses. (In general, these alloys require about 10% less current than the carbon steels.)

Electrode Selection – The electrode selected to weld a corrosion-resistant cast alloy should deposit the same alloy content as the casting. To accomplish this, the electrode core and coating are adjusted to compensate for melting losses that occur during welding. Particular care should be exercised with the corrosion-resistant cast alloys of low carbon content to assure that the electrode does not add more carbon.

For the heat-resistant alloys, welding electrodes ca-pable of depositing high carbon weld metal help prevent cracking. The varying levels of silicon present in the several heat-resisting alloy compositions, sometimes require an adjustment of the carbon introduced into the weld deposit by the electrode. This is done by the elec-trode manufacturer to maintain the proper carbon-silicon ratio in the weld deposit and thus eliminate crack-ing.

Lime coated electrodes are usually preferred for welding high-alloy castings. All welding slag must be removed after welding, for when service temperatures approach the melting point of the slag, severe metal attack can occur.

B. Oxy-Acetylene Welding–Oxy-acetylene welding may be used on the heat-resistant types but this type of welding should not be used on chromium-nickel cast-ings intended for corrosion-resistant service. For the heat-resistant grades, a carburizing flame rich in acety-lene is suggested, especially if service conditions include a carburizing atmosphere.

2. Welding the Straight Chromium Alloys

The straight chromium alloys are divided into harden-able and non-hardenable groups.

Figure 6–Tool Bit Angles for High Speed Steel Tools for Machining Stainless Steel Castings.

52

The virtue of the hardenable alloys is that their use permits refinement of the grain size, and also the devel-opent of a variety of mechanical properties by suitable heat treating procedures. This hardenability, however, necessitates extra care when welding, for it can result in brittle structures in the weld deposits and heat-affected zone if the weld casting is allowed to cool down to room temperature in air. Heat treatment is necessary to re-store ductility and must be done immediately following welding, and care must be taken that the castings re-ceive no rough handling between welding and heat treating. Cracking and distortion can be minimized by welding the castings only after annealing and not in the as-cast condition.

The non-hardenable straight chromium alloys contain 18 to 30% Cr, and, although they do not harden when cooled rapidly, grain growth and brittleness result. Gen-erally speaking, these grades have limited weldability and call for extreme care in welding and in composition control (i.e., nickel content should be kept near the maximum allowable in the specification).

A. Arc Welding – In arc welding straight chromium heat and corrosion-resistant castings, the welding cur-rents used are qenerally lower than those employed for

carbon steel because of their greater electrical resis-tance and lower melting points.

Welding Current – Reverse polarity direct current is most commonly used in welding straight chromium alloys; however, AC can be employed. The type of welding current used, whether direct or alternating, is a function of the flux casting present on the electrode. Table XIII shows suggested electrical settings and elec-trode sizes for the various section thicknesses.

Electrode Selection – In selecting the proper elec-trode, it is important that the weld metal have the same corrosion and heat-resistant properties as the parent metal. The composition of the casting and commercial electrodes are not exactly the same, for the electrode is generally made to an AWS specification as listed it Tables X and XI.

Lime coated electrodes are generally used for weld-ing the straight chromium alloys, for they are considered to give cleaner weld metal and allow for better bead build-up than the titania or titania lime-coated rod.

B. Oxy-Acetylene Welding – Gas welding does not find wide application for the straight chromium alloys and is limited to those with less than 14% chromium.

TABLE XII Electrical Settings and Electrode Size for Welding

Chromium-Nickel Alloy Castings

TABLE XIII Electrical Settings and Electrode Size for Welding

Straight Chromium Alloy Castings

Casting Thickness at Weld,

Electrode Diameter,

Amperes Arc Volts,

max

in. In.

Under 1/16 1/16 25-40 22 5/64 35-55 23

1/16-7/64 3/32 45-70 24 7/64-3/16 1/8 70-105 25 3/16-1/2 5/32 100-140 25 1/2 and above 3/16 130-180 26

Casting Thickness at Weld.

Electrode Diameter,

Amperes Volts

in in

Under 1/16 5/64 25-40 20-22 1/16-9/64 3/32 or 1/8 50-90 22-24 9/64-3/16 1/8 or 5/32 90-125 22-24 3/16- 1/2 5/64 or 3/16 100-150 23-27 1/2 and above 3/16 125-175 26-29

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