Mahdi Azizieh Metallurgy or Metalorgy History Fabrication of Metal Parts Casting Powder Metallurgy...

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


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)


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%)


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


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


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


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

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


Sulfur (S) (11xx) Imparts brittleness Improves machining Okay if combined with Mn Some free-machining steels contain 0.08% to 0.15% S


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


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


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


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


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


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

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.

http://www.special-steel.net/product_cate/Stainless-Steel

Mahdi Azizieh Metallurgy or Metalorgy History Fabrication of Metal Parts Casting Powder Metallurgy...

Documents

Transcript of Mahdi Azizieh Metallurgy or Metalorgy History Fabrication of Metal Parts Casting Powder Metallurgy...