1. Metal Alloys Formation
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2. Objective To have an understanding of
Manufacturing of steels & their products,
Alloy designation,
Classification,
Properties & uses of various types …..Plain/ alloy/tool etc,
Effects of common alloying elements
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3. Metal Alloys Most engineering metallic materials are alloys.
Elemental metals are generally very soft and not very usable.
Metals are alloyed to enhance their properties, such as
strength,
hardness or
corrosion resistance,
and to create new properties, such as
superconductivity and
shape memory effect.
Engineering metal alloys can be broadly divided into
Ferrous alloys and
Non-ferrous alloys
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4. Engineering Materials

5. Classes of Metals Metal Non-ferrous Ferrous Cast irons Steels
Grey iron
Nodular iron
White iron
Malleable iron
Alloy cast irons
Carbon
Low Alloy
High Alloy
Low-C
Medium-C
High-C
Tool (Mo,V,W,Cr, Ni)
Stainless (Cr, Ni) ……
High-
strength low-alloy
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6. Steel
Structural framing
Roofing / Cladding
Interior products
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7. The Whole Spectrum of Steel Products!
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8. Alloy Designation
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9. AISI - SAE Classification System AISI XXXX
American Iron and Steel Institute (AISI)
classifies alloys by chemistry
4 digit number
1st number is the major alloying element
2nd number designates the subgroup alloying element OR the relative percent of primary alloying element.
last two numbers approximate amount of carbon (expresses in 0.01%)
American Iron and Steel Institute (AISI)
classifies alloys by chemistry
started by Society of Automotive Engineers (SAE)
provide standardization of steel used in the automotive industry
expanded by AISI to include all engineering materials
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%
1080 steel would be plain carbon steel with 0.80% carbon
4340 steel would be Mo-Cr-Ni alloy with 0.40% carbon
Refer to table 6-2 in book

10. Carbon Steels and Low Alloy Steels
Alloy Designation Alloy Designation
AISI: American Iron and Steel Institute
SAE: Society of Automotive Engineers
ASTM: American Society for Testing and Materials
UNS: Unified Numbering System
AISI Grade X1X2X3X4
Older, but still widely used
1040
Fe-0.4%C
2520
Fe-5%Ni-0.2%C
10, 11, 12 plain C steel
13 Mn steel
2x Ni steel, x=%Ni
3x Ni-Cr Steel, x=%Ni+Cr
4x Mo Steel, x=%Mo
5x Cr steels, x=%Cr
6x Cr-V Steels, x=%Cr+V
7x W-Cr Steels, x=%W+C
9x Si-Mn Steels, x=%Si+Mn
X1X2
Primary alloying elements
Carbon content
5195 =?
eg. 15 = 0.15%C
Fe-1%Cr-0.95%C
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11. What is a steel and alloy of?
Iron (Fe) and Carbon (C)
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12. Plain Carbon Steels
An alloy of Fe & C whose properties depends only upon the %age of Carbon present in it.
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13. Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels
Grey iron
Nodular iron
White iron
Malleable iron
Alloy cast irons
Carbon
Low Alloy
High Alloy
Low-C
Medium-C
High-C
Tool (Mo,V,W,Cr, Ni)
Stainless (Cr, Ni) ……
High-
strength low-alloy
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14. Plain Carbon Steel vs. Alloy Steel
Lowest cost
Should be considered first in most application
Classifications
Low Carbon Steel
Medium Carbon Steel
High Carbon Steel
Plain Carbon Steel
Lowest cost
Should be considered first in most application
3 Classifications
Low Carbon Steel
Less than 0.20% Carbon
Good formability and weldability
Lacks hardenability (Difficult to harden)
Medium Carbon Steel
0.20% to 0.50% Carbon
Good toughness and ductility
Poor Hardenability (typically limited to water quench)
High Carbon Steel
Greater than 0.50% carbon
Low formability
High hardness and wear resistance
Poor hardenability (quench cracking occurs)
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15. Plain Carbon Steels: General Properties
Yield strength: 300MPa (mild steels) MPa (high C steels)
Tensile strength: MPa
Ductility: EL%
Young’s modulus: 210 MPa.
Divided into
low (<0.3%C),
medium ( %C) and
high ( % C) carbon levels
Increasing C content increases strength & hardness, but decreases ductility & toughness
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16. Low Carbon Steel Carbon < 0.3wt%
Used wherever soft, deformable materials are needed
E.g., structural sections, rivets, nails, wire, pipe.
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17. Medium Carbon Steels Carbon = 0.3 - 0.6wt%
Used where higher strength is required
E.g., gears, shafts, axles, rods, etc.
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18. High Carbon Steels Carbon = 0.6 - 1.2wt%
used where high hardness is required
E.g. hammers, chisels, drill, springs.
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19. Mild steel panels for easy shaping high-carbon steel springs
Medium-carbon steel chassis for strength and toughness
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20. Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels
Grey iron
Nodular iron
White iron
Malleable iron
Alloy cast irons
Carbon
Low Alloy
High Alloy
Low-C
Medium-C
High-C
Tool
Tool (Mo,V,W,Cr, Ni)
Stainless (Cr, Ni) ……
High-
strength low-alloy
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21. Alloy Steel
Alloy steel may be defined as one whose characteristics properties are due to some elements other than Carbon. Although all Plain-Carbon steels contain moderate amounts of Mn & Si, but they are not considered alloy steels because the principal function of Mn & Si is to act as de-oxidizer during steel manufacturing process.
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22. Why alloying is necessary?
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23. Why alloying is necessary?
Many purposes, some of the most important are:-
i. increase harden-ability,
ii. reduce danger of warpage,
iii. improve strength & toughness at high & low temperatures,
iv. resist grain growth at elevated temperature,
v. improve wear, corrosion, fatigue & creep resistance.
vi. improve machine-ability,
vii. improve magnetic properties.
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24. Alloying Elements used in Steel
Nickel (Ni) (2xxx)
2% to 5%
Increases toughness
Increases impact resistance
12% to 20% with low amounts of C possess great corrosion / scaling resistance
universal grain refiner in alloy steels
unfortunately is a powerful graphitiser.
Invar
contains 36% Ni
virtually no thermal expansion
used for sensitive measuring devices
Nickel (Ni)
added to steel to increase toughness and impact resistance
2% to 5%
typically used in combination with Chromium and Molybdenum
12% to 20% Nickel AND low amounts of Carbon
possess great corrosion resistance
Invar
contains 36% Ni
virtually no thermal expansion
used for sensitive measuring devices
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25. Alloying Elements used in Steel
Chromium (Cr) (5xxx)
Usually < 2%
increases hardenability and strength
5 % Cr steels used for making forging dies
typically used in combination with Ni and Mo
10.5% < Cr < 27% = stainless steel –
used for corrosion resistance
Improves non-scaling properties
Causes grain growth
Reduces toughness
Chromium (Cr)
Usually less than 2%
used primarily to increase hardenability and strength
typically used in combination with Ni and Mo
chromium carbides can enhance wear resistance
Molybdenum (Mo)
Usually less than 0.3%
used to increase hardenability and strength
Mo-carbides help increase creep resistance at elevated temps
typical application is hot working tools
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26. Alloying Elements used in Steel
Molybdenum (Mo) (4xxx)
Usually < 0.3%
has strong carbide stabilizing influence
increases hardenability and strength
Mo-carbides help increase creep resistance at elevated temps
imparts some sluggishness to tempering influences
improves the tensile strength & sp. heat resistance
has favorable influence on the welding properties.
Steel with higher contents tend to be difficult to forge
typical application is hot working tools
Chromium (Cr)
Usually less than 2%
used primarily to increase hardenability and strength
typically used in combination with Ni and Mo
chromium carbides can enhance wear resistance
Molybdenum (Mo)
Usually less than 0.3%
used to increase hardenability and strength
Mo-carbides help increase creep resistance at elevated temps
typical application is hot working tools
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27. Alloying Elements used in Steel
Manganese (Mn)
acts as de-oxidizer during steel manufacturing
combines with sulfur (MnS) to prevent brittleness & improves machining
forms stable Carbides
>1%
increases hardenability
improves strength, wear resistance of steel
11% to 14%
increases hardness
good ductility
high strain hardening capacity
excellent wear resistance
Ideal for impact resisting tools
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)
usually not desired in steel because it will impart brittleness, but okay if combined with Mn
Some free-machining steels contain 0.08 to 0.15% S
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28. Alloying Elements used in Steel
Vanadium (V)
Usually 0.03% to 0.25%
has strong carbide-forming tendency.
stabilities martensite and increases hardenability.
induces resistance to softening at high temperatures once the steel is hardened
increases hot hardness properties in High Speed & Tool steels by increasing cutting properties.
increases strength without loss of ductility
Like Nickel it restrains grain growth
Vanadium (V)
Usually 0.03% to 0.25%
Va-carbides help to increase strength without loss of ductility
elastic limit, yield point, and impact strength
Tungsten (W)
helps to form stable carbides
increases hot hardness
used in tool steels
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29. Alloying Elements used in Steel
Tungsten (W)
helps to form stable carbides
renders transformations very sluggish - hence, once hardened, a steel resists tempering influences.
increases hot hardness
used as cutting tool steels
Vanadium (V)
Usually 0.03% to 0.25%
Va-carbides help to increase strength without loss of ductility
elastic limit, yield point, and impact strength
Tungsten (W)
helps to form stable carbides
increases hot hardness
used in tool steels
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30. Alloying Elements used in Steel
Sulfur (S) (11xx)
Imparts brittleness
Okay if combined with Mn
Improves machining
Some free-machining steels contain 0.08% to 0.15% S
Sulfur (S)
usually not desired in steel because it will impart brittleness,
but okay if combined with Mn
Some free-machining steels contain 0.08 to 0.15% S
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31. Alloying Elements used in Steel
Boron (B) (14xx)
for low carbon steels, can drastically increase hardenability
improves machinablity and cold forming capacity
Aluminum (Al))
Boron (B)
for low carbon steels, B can drastically increase hardenability
as the carbon content goes up the hardenabilty goes down
improves machinablity and cold forming capacity
Aluminum (Al)
deoxidizer
0.95% to 1.30%
produce Al-nitrides during nitriding
deoxidizer
0.95% to 1.30%
produce Al-nitrides during nitriding
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32. Alloying Elements used in Steel
Copper (Cu)
0.10% to 0.50%
increases corrosion resistance
Reduces surface quality and hot-working ability
used in low carbon sheet steel and structural steels
Copper (Cu)
0.10% to 0.50%
helps to increase corrosion resistance
surface quality and hot-working ability decline
used in low carbon sheet steel and structural steels
Silicon (Si)
about 2%
helps to increase strength without loss of ductility
used in structural steels and spring steels
also helps to enhance magnetic properties
Silicon (Si)
About 2%
increases strength without loss of ductility
enhances magnetic properties
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33. Alloy Steel >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
Alloy Steel
What classifies a steel as an Alloy Steel
> 1.65%Mn, > 0.60% Si, or >0.60% Cu
Definite or minimum amount of an alloying element is specified
Most alloying elements added to steel are < 5%
to increase strength and hardenability
Most alloying elements added to steel are > 20%
to improve corrosion resistance or stability at high or low temps
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34. High Strength Low Alloy Steels
Low alloy =  alloying elements <10%
Yield strength : MPa
Tensile strength: MPa
Ductility : EL%
Young’s modulus: 200 MPa (alloying generally reduces Young’s Modulus)
Uses
Used where high strength or hardness is needed – eg high strength bolts, connecting rods, springs, torsion bars, ball bearings.
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35. Classes of Metals Metal Alloys Non-ferrous Ferrous Cast irons Steels
Grey iron
Nodular iron
White iron
Malleable iron
Alloy cast irons
Carbon
Low Alloy
High Alloy
Low-C
Medium-C
High-C
Tool
Tool (Mo,V,W,Cr, Ni)
Stainless (Cr, Ni) ……
High-
strength low-alloy
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36. Tool Steels
A class of (usually) highly alloyed steels designed for use as industrial cutting tools, dies, and molds
To perform in these applications, they must possess
high strength, hardness, hot hardness, wear resistance, and toughness under impact
Tool steels are heat treated
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37. AISI Classification of Tools Steels
T, M High‑speed tool steels ‑ cutting tools in machining
H Hot‑working tool steels ‑ hot‑working dies for
forging, extrusion, and die‑casting
D Cold‑work tool steels ‑ cold working dies for
sheet metal press-working, cold extrusion, and forging
W Water‑hardening tool steels
S Shock‑resistant tool steels ‑ tools needing high toughness, as in sheet metal punching and bending
P Mold steels ‑ molds for molding plastics and rubber
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38. Tool Steels Carbon tool steels: 0.8~1.2%C
High alloy tool steels are often alloyed with Mo, V, W, Cr and/or Ni
E.g., HSS, W-Cr-V (18-4-1)
Yield strength: MPa
Tensile strength: up to 2000MPa
Ductility: EL% 5-15
Young’s modulus: 200 MPa (alloying generally reduces Young’s Modulus)
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39. Tool Steels Uses Used where extreme hardness is required.
Ductility/toughness usually sacrificed
E.g. Moulds and dies, saws, cutting tools, punches
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40. Stainless Steel (SS)
Highly alloyed steels designed for corrosion resistance
Principal alloying element is chromium, usually greater than 11.5%
Cr forms a thin impervious oxide film that protects surface from corrosion
“Stainless-ness” comes from the formation of a self-repairing Cr2O3 thin, adherent & impervious oxide film that protects or passivates the underlying steel.
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41. Stainless Steel (SS)
Nickel (Ni) is another alloying ingredient in certain SS to increase corrosion protection
Carbon is used to strengthen and harden SS, but high C content reduces corrosion protection since chromium carbide forms to reduce available free Cr, therefore Carbon content is kept very low - < 0.1% to avoid Cr3C2 formation
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42. Properties of Stainless Steels
In addition to corrosion resistance, stainless steels are noted for their combination of strength and ductility
While desirable in many applications, these properties generally make SS difficult to work in manufacturing
Significantly more expensive than plain C or low alloy steels
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43. Types of Stainless Steel
Classified according to the predominant phase present at ambient temperature:
Austenitic stainless ‑ typical composition 18% Cr and 8% Ni
Ferritic stainless ‑ about 11.5% to 27% Cr, low C (0.25% max), and no Ni
Martensitic stainless ‑ as much as 18% Cr but no Ni, higher C content ( %) than ferritic stainless
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44. Additional Stainless Steels
Traditional stainless steels developed in early 1900s
Several additional high alloy steels have been developed and are also classified as stainless steels:
4. Precipitation hardening stainless ‑ typical composition = 17% Cr and 7%Ni, with additional small amounts of alloying elements such as Al, Cu, Ti, and Mo
5. Duplex stainless ‑ mixture of austenite and ferrite in roughly equal amounts
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45. Stainless Steels - Typical Mechanical Properties
Yield strength : MPa
Tensile strength : MPa
Ductility : EL% 2-20
Young’s modulus:~170 MPa (alloying reduces Young’s Modulus)
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46. Designation Scheme for Stainless Steels
Three‑digit AISI numbering scheme
First digit indicates general type, and last two digits give specific grade within type
Examples:
Type 302 – Austenitic SS
18% Cr, 8% Ni, 2% Mn, 0.15% C
Type 430 – Ferritic SS
17% Cr, 0% Ni, 1% Mn, 0.12% C
Type 440 – Martensitic SS
17% Cr, 0% Ni, 1% Mn, 0.65% C
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47. Assignment Alloy steels Cr steels Ni steels Ni-Cr steels Mn steels
Mo- steels
V-steels
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48. Thanks
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