Material of Construction

CLASSIFICATION OF MATERIALS

A vast range of materials are available. Materials can be classified as follows.

Engineering Materials

Metallic Non-Metallic

Ferrous FRP

Ceramics

HDPE

Concrete

Non-Ferrous

Cast Iron

Carbon Steels

Aluminum

ZirconiumNickel & Alloys

Titanium

Copper & AlloyGlass

Alloy Steels

Iron is classified based on the method of manufacturing & the alloying elements used to enhance its physical & mechanical properties.

CLASSIFICATION OF IRON (Contd)

AlloySteel Carbon

Steel

PuddledIron

PigIron

WhiteCast IronGrey

Cast Iron

WroughtIron

IngotIron

MalleableCast Iron

CastIron

Iron

Iron has 3 phases when it is heated from lower temperature to high temperature. Alpha Iron: Occurs from normal temperature to 910C. Crystals are of b.c.c lattice structure.

Gamma Iron: Occurs from 910C to 1400C. Crystals are of f.c.c lattice structure.

Delta Iron: Occurs from 1400C to 1539C. Crystals are of b.c.c lattice structure.

CLASSIFICATION OF IRON

TYPES OF SPACE LATTICE

The mechanical properties of a particular metal are related to the patterns found in its lattice structure.

Types of lattice structures are: Body centered cubic (b.c.c.) structure:

Atoms are arranged at each corner of cube & one on centre of body of cube.

This arrangement is found in iron.

TYPES OF SPACE LATTICE (Contd)

Face centered cubic (f.c.c.) structure: Atoms are arranged at each corner of cube & centre of each

face of the cube. Aluminum, Copper, nickel & most ductile metals have f.c.c.

structure.

TYPES OF SPACE LATTICE (Contd)

Closed packed hexagonal (c.p.h.) structure: Atoms are arranged in 3 layers. Top & bottom layers consist of 6 atoms in a hexagon with 1

atom at the centre. Middle layer has 3 atoms in the form of triangle. Least ductile metals like zinc & magnesium have this

structure.

IRON-IRON CARBIDE (Fe-Fe3C) DIAGRAM

IRON-IRON CARBIDE (Fe-Fe3C) DIAGRAM (Contd)

There are 5 main phases of steel, viz., ferrite, cementite, austenite, pearlite and martensite.

Ferrite: Solid solution with up to 0.025% Carbon. It is soft, weak and ductile. Hardness is as low as 50 to 100 BHN. Also known as alpha iron.

Cementite: It is a compound of carbon and iron carbides. It is hard and strong. Hardness is in the range of 1400 BHN.


Austenite: Solid solution with up to 1.7% Carbon in gamma iron. Occurs due to interface reaction of ferrite & cementite. Unstable at room temperature. The addition of certain other metals, such as manganese and nickel, can

stabilize the austenitic structure even at room temperature. Soft, ductile, malleable and non-magnetic. Also known as gamma iron.

Pearlite: When steel with 0.83% Carbon is cooled from austenite phase, the metal

starts transforming into pearlite from 723C. When steel with 1.2% Carbon is cooled, cementite precipitates first from

the grain boundaries up to 723C & the remaining metal transforms to pearlite.


Martensite: Formed in carbon steels by fast and continuous cooling of austenite to

temperatures 205C to 315C or even lower. It has tetragonal crystal structure. Hardness varies from 500 to 1000 BHN depending upon carbon content.

Steel is an alloy of iron and iron-carbide. Steels are classified into carbon steel, alloy steel & stainless steel.

Carbon steel (CS): CS is an alloy of iron & carbon with varying quantities of

phosphorus & sulphur.

Alloy steel: A steel is called alloy steel when alloying elements exceeds the

limit given below: Manganese - 1.65% Silicon & Copper - 0.6%

STEEL

The effects of elements added into CS are as under: Carbon: Tensile strength increases with an increase in carbon content up to

0.83% & drops beyond this. Hardness increases. Ductility & weldability decreases.

Manganese: Tensile strength & hardness increases. Weldability decreases. Content varies from 0.2% to 0.8%.

Phosphorus: Tensile strength increases. Content varies from 0.005% to 0.12%.

STEEL (Contd)

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Sulphur: Lowers the toughness & ductility. Maximum permitted content in steel is 0.035%.

Silicon: Principal deoxidizer used in carbon steel Presence of Silicon promotes increase in grain size & deep

hardening properties. Silicon varies from 0.1% to 0.35% in carbon steel.

Copper: Copper is added up to 0.2% to increase the resistance to

atmospheric corrosion. Other elements such as nickel, molybdenum, vanadium, cobalt,

etc. are present in carbon steel in residual quantities.

STEEL (Contd)

Effects of various alloying elements in steel are as follows: Nickel: It imparts toughness, elasticity, hardness and fatigue resistance to

steel. Improves corrosion resistance. Certain heat resisting steels are produced by adding about 8% Ni

with Cr, because these two elements prevent breakdown of austeniteduring cooling to room temp.

Chromium: It increases resistance to wear. Increases strength at high temperature. Chromium tends to promote coarse-grain structure & increases

difficulty of heat treatment, this counteracted by nickel which refinesgrain size.

STEEL (Contd)

Molybdenum: Steels containing Cr & Ni become brittle if held at a temperature

between 250-500C. This can be overcome by adding 0.25% ofMolybdenum.

Addition of Mo hampers grain growth at high temperature hencemaking steel finer grained & tougher.

Manganese: Increases tensile strength Increases resistance to wear in steels with carbon content 1-1.5%. Counters the effects of sulphur.

Silicon: When used up to 2.5%, it increases the strength without decreasing

the ductility.

STEEL (Contd)

Vanadium: It gives strength & toughness to steel. It is used for providing fine grained structure over a broad range of

temperature. Boron: Improves rolling properties of steel.

Aluminum: It is used as de-oxidizer. It controls grain growth.

STEEL (Contd)

STEEL (Contd)

Stainless steel: A thin, transparent & very tough film forms on the surface of

stainless steel which is inert and does not react with manycorrosive materials.

The property of corrosion resistance is obtained by addition of Cror by adding Cr & Ni both.

Stainless steel are classified into Austenitic, Ferritic & Martensiticstainless steels.

Austenitic Stainless Steels Contains at least 24% Cr & Ni both. Individually % is not less

than 8%. Non-magnetic & non-hardenable by heat treatment but

hardened by cold working. Carbon in L grades of SS is kept below 0.03%. L grades posses good weldable properties. L grades SS are used for high corrosive service & moderate

temperatures. Dual certified grades posses corrosive resistance of L grades

& better physical strength at high temperature. Eg. Grade 304L, 316L, etc.

STEEL (Contd)

m3

m4

H grades contain carbon from 0.04% to 0.1%. Used at extremely high temperatures. Eg. Grade 304H, 316H, etc.

Ferritic Stainless Steels Difference between Cr % & 17 x C % is greater than 12.5%. Resistant to stress corrosion cracking. Magnetic & cannot be hardened by heat treatment. Can be Cold worked & refined by heat treatment. Resistance to corrosion is lesser than Austenitic SS but greater

than Martensitic SS. Eg. Grade 436.

STEEL (Contd)

Martensitic Stainless Steels Difference between Cr % & 17 x C % is less than 12.5%. Magnetic & can be hardened by heat treatment. Typical applications include highly stressed parts needing

corrosion resistance such as fasteners. Eg. Grade 410 & 410S.

Duplex Stainless Steels 2 phase alloys based on Fe-Cr-Ni. Strength, ductility, improved toughness and resistance to pitting. Eg. Grade 329.

STEEL (Contd)

What governs the material selection ?

Temperature Service Media Codes & Standards Economy Ease in fabrication Availability

MATERIAL SELECTION CRITERIA

Corrosion occurs in the following 3 ways: Uniform Corrosion Localised Corrosion Environmental Corrosion

Uniform Corrosion can be reduced by proper selection of material Localized Corrosion can be reduced by proper design of

components. Environmental corrosion can be prevented by external surface

treatment, controlling the corrosion environmental parameters and keeping stresses at lower level.

TYPES OF CORROSION

MATERIAL SELECTION BASED ON TEMPERATURE

Temp (C)

Matl. Plate Pipe Forgings Fittings Tube Bolting

Cryogenic Temperature-254To

-196

SS SA-240 304, 304L, 347, 316, 316L

SA-312 304, 304L, 347, 316, 316L

SA-182 F304, F304L, F347, F316, F316L

SA-403 304, 304L, 347, 316, 316L

SA-213 TP304, TP304L, TP316, TP316L

SA-320 B8 with SA-194 8

-196To-80

9 Ni SA-353/553 A

SA-333 8 SA-522 SA-420 WPL8

SA-334 8

Low Temperature

-80To-60

3 Ni

SA-203 E SA-333 3 SA-350 LF3 SA-420 WPL3

SA-334 3 SA-320 L7 with SA-194 4

-60To-45

CS SA-537 Cl.1 SA-333 3 SA-350 LF3 SA-420 WPL3

SA-334 3

MATERIAL SELECTION BASED ON TEMPERATURE (Contd)

Temp (C)


Low Temperature (contd)-45To-29

CS SA-516 All Grds Impact tested

SA-333 6 SA-350 LF2 SA-420 WPL6

SA-334 6 SA-320 L7 with SA-194 4

-29To0

CS SA-516 All Grds

SA-106 B SA-105/266 SA-234 WPB SA-334 6 SA-193 B7 with SA-194 2H

Intermediate Temperature

0To

343

CS SA-516 All Grds

SA-106 B SA-105/266 SA-234 WPB SA-179 SA-193 B7 with SA-194 2HSS SA-240

304L, 316, 321

SA-312 TP304L, 316L, 321

SA-182 F304L, 316L, 321

SA-403 304L, 316L, 321

SA-213 TP304L, 316L, 321


Temp (C)


Intermediate Temperature (contd)343To

427

CMo

SA-204 B SA-335 1 SA-182 F1 SA-234 WP1 SA-209 T1 SA-193 B7 with SA-194 4

LAS SA-387 11 Cl.1/Cl.2

SA-335 P11 SA-182 F11 SA-234 WP11 SA-213 T11

SS SA-240 304L, 316, 321

SA-312 TP304L, 316L, 321

SA-182 F304L, 316L, 321

SA-403 304L, 316L, 321

SA-213 TP304L, 316L, 321

Elevated Temperature

427To

538

LAS SA-387 11/12 Cl.1/Cl.2

SA-335 P11/12

SA-182 F11/12

SA-234 WP11/12

SA-213 T11/12

SA-193 B16 w SA-194 4


Temp (C)


Elevated Temperature (contd)427To

500

SS SA-240 304, 316, 321

SA-312 TP304, 316, 321

SA-182 F304, 316, 321

SA-403 304, 316, 321

SA-213 TP304, 316, 321

SA-193 B16 with SA-194 4

538To

593

LAS SA-387 22/21 Cl.1/Cl.2

SA-335 P22 SA-182 F22 SA-234 WP22

SA-213 T22 SA-193 B5 with SA-194 3

500To

815

SS SA-240 304H, 316H, 321H

SA-312 TP304H, 316H, 321H

SA-182 F304H, 316H, 321H

SA-403 304H, 316H, 321H

SA-213 TP304H, 316H, 321H

SA-193 B8 with SA-194 8

Testing the selected material to confirm the desired properties. The following tests/analysis must be carried out:

Chemical (ladle) analysis Tensile test Impact test Hardness test

CONFIRM SELECTION OF APPROPRIATE MATERIAL

THANK YOU

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Material of Construction