Upload
savion-sprague
View
231
Download
9
Tags:
Embed Size (px)
Citation preview
Key to SteelMahdi Azizieh
Metallurgy or Metalorgy History Fabrication of Metal Parts
◦ Casting◦ Powder Metallurgy◦ Rolling◦ Forging◦ Extrusion◦ Welding◦ …
What is the “Metallurgy”
◦ Wrought Iron◦ Cast Iron◦ Steel
Alloying Elements (C, Mn, Si, Ni, Cr, V, Mo, Ti, Nb, Al)
Ferrous alloys
Iron and Steel Making Process
Hypereutectoid composition – proeutectoid cementite
Consider C0 = 1.13 wt% C
Fe 3
C (
cem
entit
e)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
g(austenite)
g+L
g +Fe3C
a +Fe3C
L+Fe3C
d
(Fe) C, wt%C
T(°C)
727°CDT
0.7
6
0.0
22
1.13
c11f37S
tren
gth
Duc
tility
Martensite T Martensite
bainite fine pearlite
coarse pearlite spheroidite
General Trends
Possible Transformations
Coarse pearlite (high diffusion rate) and (b) fine pearlite
c11f15
- Smaller T: colonies are larger
- Larger T: colonies are smaller
10 103 105
time (s)10-1
400
600
800
T(°C)Austenite (stable)
200
P
B
TE
0%
100%
50%
A
A
Bainite: Non-Equil Transformation Products
elongated Fe3C particles in a-ferrite matrix diffusion controlled a lathes (strips) with long rods of Fe3C
100% bainite
100% pearlite
Martensite
Cementite
Ferrite
single phase body centered tetragonal (BCT) crystal structure BCT if C0 > 0.15 wt% C
Diffusionless transformation BCT few slip planes hard, brittle % transformation depends only on T of rapid cooling
Martensite Formation• Isothermal Transformation Diagram
10 103 105 time (s)10-1
400
600
800
T(°C)Austenite (stable)
200
P
B
TE
0%
100%50%
A
A
M + AM + A
M + A
0%50%90%
Martensite needlesAustenite
An micrograph of austenite that was polished flat and then allowed to transform into martensite. The different colors indicate the displacements caused when martensite forms.
Plain Carbon Steel
Plain Carbon SteelLowest cost Should be considered first in most application
3 Classifications Low Carbon (less than 0.3% carbon) Med Carbon (0.3% to 0.6%) High Carbon (0.6% to 0.95%)
Plain Carbon Steel
Again, alloy of iron and carbon with carbon the major strengthening element via solid solution strengthening.
If carbon level high enough (greater than 0.6%) can be quench hardened (aka: dispersion hardening, through hardened, heat treated, austenized and quenched, etc..).
Can come in HRS and CRS options The most common CRS are 1006 through
1050 and 1112, 1117 and other free machining steels
1. Low Carbon (less than 0.3% carbon)• Low strength, good formability
• If wear is a potential problem, can be carburized (diffusion hardening)
• Most stampings made from these steels• AISI 1008, 1010, 1015, 1018, 1020, 1022, 1025
2. Med Carbon (0.3% to 0.6%)• Have moderate to high strength with fairly good ductility• Can be used in most machine elements• AISI 1030, 1040, 1050, 1060*
3. High Carbon (0.6% to 0.95%)• Have high strength, lower elongation• Can be quench hardened• Used in applications where surface subject to abrasion – tools,
knives, chisels, ag implements.• AISI 1080, 1095
Plain Carbon Steel
Alloy Steel Again, elements added to steel can
dissolve in iron (solid solution strengthening):◦ Increase strength, hardenability, toughness,
creep, high temp resistance. Alloy steels grouped into low, med and
high-alloy steels.◦ High-alloy steels would be the stainless steel
groups.◦ Most alloy steels you’ll use fall under the
category of low alloy.
Alloy Steel > 1.65%Mn, > 0.60% Si, or >0.60% Cu Most common alloy elements:
◦ Chromium, nickel, molybdenum, vanadium, tungsten, cobalt, boron, and copper.
Low alloy: Added in small percents (<5%) ◦ increase strength and hardenability
High alloy: Added in large percents (>20%)◦ i.e. > 10.5% Cr = stainless steel where Cr
improves corrosion resistance and stability at high or low temps
Alloying Elements used in Steel
Manganese (Mn) combines with sulfur to prevent
brittleness >1%
◦ increases hardenability 11% to 14%
◦ increases hardness◦good ductility◦high strain hardening capacity◦excellent wear resistance
Ideal for impact resisting tools
Alloying Elements used in Steel
Sulfur (S) Imparts brittleness Improves machineability Okay if combined with Mn Some free-machining steels contain 0.08% to 0.15% S
Examples of S alloys:◦11xx – sulfurized (free-cutting)
Alloying Elements used in Steel
Nickel (Ni) Provides strength, stability and
toughness, Examples of Ni alloys:◦30xx – Nickel (0.70%), chromium
(0.70%)◦31xx – Nickel (1.25%), chromium
(0.60%)◦32xx – Nickel (1.75%), chromium
(1.00%)◦33XX – Nickel (3.50%), chromium
(1.50%)
Alloying Elements used in Steel
Chromium (Cr) Usually < 2% increase hardenability and strength Offers corrosion resistance by forming stable oxide surface typically used in combination with Ni and Mo
◦ 30XX – Nickel (0.70%), chromium (0.70%)◦ 5xxx – chromium alloys◦ 6xxx – chromium-vanadium alloys◦ 41xxx – chromium-molybdenum alloys
Molybdenum (Mo) Usually < 0.3% increase hardenability and strength Mo-carbides help increase creep resistance at elevated
temps◦ typical application is hot working tools
Alloying Elements used in Steel
Vanadium (V) Usually 0.03% to 0.25% increase strength
◦without loss of ductilityTungsten (W)
helps to form stable carbides increases hot hardness
◦used in tool steels
Alloying Elements used in Steel
Copper (Cu) 0.10% to 0.50% increase corrosion resistance Reduced surface quality and hot-working
ability used in low carbon sheet steel and
structural steelsSilicon (Si)
About 2% increase strength without loss of
ductility enhances magnetic properties
Alloying Elements used in Steel
Boron (B) for low carbon steels, can drastically increase hardenability
improves machinablity and cold forming capacity
Aluminum (Al) deoxidizer 0.95% to 1.30% produce Al-nitrides during nitriding
Break
Other steel standards : SAE-AISI
◦ Society of Automotive Engineers ; American Iron and Steel Institute
ASTM◦ American Standards for Testing and Materials
AMS◦ Aerospace Materials Specifications
DIN◦ Deutsches Institut fur Normung
JIS◦ Japanese Industrial Standards Committee
UNS◦ Unified Numbering System
AISI - SAE Classification System
American Iron and Steel Institute (AISI)
classifies alloys by chemistry 4 digit number
◦1st number is the major alloying agent
◦2nd number designates the subgroup alloying agent
◦ last two numbers approximate amount of carbon (expresses in 0.01%)
Plain Carbon Steel vs. Alloy Steel
Plain Carbon Steel (10xx) Lowest cost Should be considered first in most application
3 Classifications ◦Low Carbon Steel◦Medium Carbon Steel◦High Carbon Steel
Plain Carbon Steel (10xx)
1018◦Low carbon Yield strength 55ksi
1045◦Medium carbon Yield strength 70ksi
ASTM A36 or A37 – aka structural steel◦Low carbon Yield strength 36ksi
12L14◦Low carbon Yield strength 70ksi
1144◦Medium carbon Yield strength 95ksi
Plain Carbon Steel vs. Alloy Steel
Alloy Steel > 1.65%Mn, > 0.60% Si, or >0.60% Cu Most common alloy elements:
◦ Chromium, nickel, molybdenum, vanadium, tungsten, cobalt, boron, and copper.
Added in small percents (<5%) ◦ increase strength and hardenability
Added in large percents (>20%)◦ improve corrosion resistance or stability
at high or low temps
Alloying Elements used in Steel
Sulfur (S) (11xx) Imparts brittleness Improves machining Okay if combined with Mn Some free-machining steels contain 0.08% to 0.15% S
Alloying Elements used in Steel
Nickel (Ni) (2xxx) Increase toughness Increase impact resistance 2% to 5% 12% to 20% with low amounts of C
possess great corrosion resistance Invar
◦contains 36% Ni◦virtually no thermal expansion◦used for sensitive measuring devices
Alloying Elements used in Steel
Chromium (Cr) (5xxx) Usually < 2% increase hardenability and strength typically used in combination with Ni and Mo 10.5% < Cr < 27% = stainless steel – used for
corrosion resistanceMolybdenum (Mo) (4xxx)
Usually < 0.3% increase hardenability and strength Mo-carbides help increase creep resistance at
elevated temps◦ typical application is hot working tools
Alloying Elements used in Steel
Boron (B) (14xx) for low carbon steels, can drastically increase hardenability
improves machinablity and cold forming capacity
Aluminum (Al) deoxidizer 0.95% to 1.30% produce Al-nitrides during nitriding
Alloying Elements used in Steel
Manganese (Mn) combines with sulfur to prevent
brittleness >1%
◦ increases hardenability 11% to 14%
◦ increases hardness◦good ductility◦high strain hardening capacity◦excellent wear resistance
Ideal for impact resisting tools
Alloying Elements used in Steel
Vanadium (V) Usually 0.03% to 0.25% increase strength
◦without loss of ductilityTungsten (W)
helps to form stable carbides increases hot hardness
◦used in tool steels
Alloying Elements used in Steel
Copper (Cu) 0.10% to 0.50% increase corrosion resistance Reduced surface quality and hot-working
ability used in low carbon sheet steel and
structural steelsSilicon (Si)
About 2% increase strength without loss of
ductility enhances magnetic properties
Examples:
2350
2550
4140
1060
Corrosion Resistant Steel
Stainless Steel 10.5% < Cr < 27% = stainless steel
– used for corrosion resistance AISI assigns a 3 digit number
◦ 200 and 300 … Austenitic Stainless Steel
◦ 400 … Ferritic or Martensitic Stainless Steel
◦ 500 … Martensitic Stainless Steel
Stainless Steels
Excellent corrosion resistance Contain 12 to 30% Chromium
◦ Cr oxidizes easily and forms a thin continuous layer of oxide that prevents further oxidation of the metal
Cr is a ferrite stabilizer
Austenite is restricted to a small region of the phase diagram
•Ferritic Stainless Steels are essentially Fe-Cr Alloys• Ferrite phase (bcc structure)•Inexpensive, high strength
Stainless Steels
Austenitic Stainless Steels◦ Nickel is an austenite stabilizer. The addition of
both Cr and Ni results in the austenite (g, fcc) phase being retained to room temperature
◦ The austenite phase is very formable (fcc structure)
◦ Ni makes these alloys expensive Martensitic Stainless Steels
◦ Have both Cr and C◦ There is more Cr than in ferritic SS since Cr tends
to form Cr23C6, which removes available Cr for corrosion protection
◦ Can be heat treated to high strength
UNS letter S indicates stainless steel
Stainless Steel Family
Tool Steel Categories
Tool Steel Types
High alloy content and thus high hardenability
Melted by electric furnace for cleanliness and alloy content control
Melted in small heats and subjected to tight quality control
Tool Steel
Wear Resistant, High Strength and Tough
High Carbon steels Modified by alloy additions AISI-SAE Classification
◦Letter & Number Identification
Tool Steel
Classification Letters pertain to significant
characteristic◦ W,O,A,D,S,T,M,H,P,L,F◦ E.g. A is Air-Hardening medium alloy
Numbers pertain to material type◦ 1 thru 7◦ E.g. 2 is Cold-work
Tool Steel AISI-SAE tool steel grades[1]
Defining property AISI-SAE grade Significant characteristics
Water-hardening W
Cold-working
O Oil-hardening
A Air-hardening; medium alloy
D High carbon; high chromium
Shock resisting S
High speed
T Tungsten base
M Molybdenum base
Hot-working HH1-H19: chromium baseH20-H39: tungsten baseH40-H59: molybdenum base
Plastic mold P
Special purposeL Low alloy
F Carbon tungsten
Overview of UNS
Axxxxx - Aluminum Alloys Cxxxxx - Copper Alloys, including Brass and Bronze Fxxxxx - Iron, including Ductile Irons and Cast Irons Gxxxxx - Carbon and Alloy Steels Hxxxxx - Steels - AISI H Steels Jxxxxx - Steels - Cast Kxxxxx - Steels, including Maraging, Stainless, HSLA, Iron-Base Superalloys L5xxxx - Lead Alloys, including Babbit Alloys and Solders M1xxxx - Magnesium Alloys Nxxxxx - Nickel Alloys Rxxxxx - Refractory Alloys
◦ R03xxx- Molybdenum Alloys ◦ R04xxx- Niobium (Columbium) Alloys ◦ R05xxx- Tantalum Alloys ◦ R3xxxx- Cobalt Alloys ◦ R5xxxx- Titanium Alloys ◦ R6xxxx- Zirconium Alloys
Sxxxxx - Stainless Steels, including Precipitation Hardening and Iron-Based Superalloys
Txxxxx - Tool Steels Zxxxxx - Zinc Alloys
AISI/SAE, ASTM, UNS
ASTM developed a parallel classification, starting with a letter A followed by numbers and other descriptors
What You Should Include in the Specifications of a Material ?
Description: e.g. steel, hot-finished, low-carbon, bar, ASTM A29 grade B
Dimension Chemical composition Mechanical properties Dimension tolerance: LWH, flatness,
etc. Finish: hot-rolled, cold rolled, patterned Special requirements: heat treatment,
texture, etc.
استاندارد آلمانی
استاندارد آلمانی
استاندارد آلمانی
Ck said control containing P, S the amount of high quality steel, Cq that cold heading steel, for example:
C20-average carbon content of ω (C) of 0.20% of carbon steel.
C20E-subject to the average carbon content of carburized ω (C) of 0.20% of case-hardened steel.
C35E - to be handled by normalizing the average carbon content of ω (C) 0.35% of carbon steel.
• representation of carbon tool steel grade carbon tool steel is also non-alloy steel, tool steel often included in the series. Grade non-alloy steel grades representation for, and the other with a suffix letter W, W1 and W2 so that different grades.
low-alloy and alloy steel grades that way only when the steel alloying elements ω (Si) ≥ 0.50%, ω (Mn) ≥ 0.80%, ω (Al) and ω (Ti) were ≥ 0.10% and ω (Cu) ≥ 0.25%, these elements can be referred to as alloying elements, which limits the value of our alloy element content (see Table 1-2) are slightly different. Grade composition of 00 × × - ×, 00 for the ω (C)% are average concentration values, × × for the content of alloying elements and symbols, concentration values in Table 1-25 regulations, - × symbol for a specific suffix. Examples are as follows
15Cr3 - average carbon content of ω (C) 0.15%, the average chromium content of ω (Cr) (3 / 4)% (0.75%) of chromium steel.
15Cr3E - average carbon content of ω (C) 0.15%, the average chromium content of ω (Cr) 0.75%, subject to the carburized chromium steel.
25CrMo56V +65 S - average carbon content of ω (C) 0.25%, the average chromium content of ω (Cr) 1.25, the average molybdenum ω (Mo) 0.60%, after a minimum tensile strength after quenching and tempering treatment is 65kgf/mm 2 (635MPa ), and by eliminating the stress of the steel handle.
When a high-alloy steel is usually a steel alloy element content> 5%, such as high alloy steel. Composition is the first known letter grade X (that high-alloy), followed by the average carbon content of that number (in the very few dollars) and discharged by the level of alloy content of alloying elements and the main alloying elements symbols, the average percentage of integer values .
X10CrNi18-8 - that ω (C) 0.10%, ω (Cr) 18%, ω (Ni) 8% of the stainless steel.