Steel is graded as a way of classification and is often categorized into four groups—Carbon, Alloy, Stainless, and Tool. Carbon Steels only contain trace amounts of elements besides carbon and iron. This group is the most common, accounting for 90% of steel production. What is the hardest steel grade? Type 440—a higher grade of cutlery steel, with more carbon, allowing for much better edge retention when properly heat-treated. It can be hardened to approximately Rockwell 58 hardness, making it one of the hardest stainless steels. Different Types of Steel Carbon Steel. Carbon steel is dull and matte in appearance and is vulnerable to corrosion Alloy Steel. Alloy steels are a mixture of several metals, including nickel, copper, and aluminum Stainless Steel

1. 1
Chapter 11 - 1
Steel and cast iron
Chapter 11 - 2

2. 2
Chapter 11 - 3
Adapted from
Fig. 11.1,
Callister 7e.
Taxonomy of Metals
Metal Alloys
Steels
Ferrous Nonferrous
Cast Irons
Cu Al Mg Ti
<1.4wt%C 3-4.5wt%C
Steels
<1.4wt%C
Cast Irons
3-4.5wt%C
Fe3C
cementite
1600
1400
1200
1000
800
600
400
0 1 2 3 4 5 6 6.7
L
g
austenite
g+L
g+Fe3C
a
ferrite
a+Fe3C
a+g
L+Fe3C
d
(Fe)
Co , wt% C
Eutectic:
Eutectoid:
0.76
4.30
727°C
1148°C
T(°C) microstructure:
ferrite, graphite
cementite
Chapter 11 - 4
1. Other terms: plain steel, mild steel, low-carbon
steel
2. Available in almost all product forms: e.g. sheet,
strip, bar, plate, tube, pipe etc.
3. Designation: e.g. 1040 steel - 0.40 wt% C
4. Up to 2 wt% C
5. Limitation for other alloying elements:
Si up to 0.6 %,
Cu up to 0.6 %
Mn up to 1.65 %
Carbon steel

3. 3
Chapter 11 - 5
Chapter 11 - 6
t11_01b_pg361
Hot-rolled steels and typical applications

4. 4
Chapter 11 - 7
AISI: the American Iron and Steel Institute
SAE: the Sociaty of Automotive and Engineering
ASTM: the American Society for Testing and
Materials
UNS: the Uniform Numbering System
Chapter 11 - 8
High alloys:

5. 5
Chapter 11 - 9
Chapter 11 -10
Designations, compositions and applications for six tool steels

6. 6
Chapter 11 -11
Chapter 11 -12

7. 7
Chapter 11 -13
Chapter 11 -14

8. 8
Chapter 11 -15
Stainless steels
1. More resistant to rusting and staining than carbon- and low-alloy
steels
2. Chromium addition, usually above 10 wt% (4-30%)
Chapter 11 -16
Stainless steels

9. 9
Chapter 11 -17
Chapter 11 -18

10. 10
Chapter 11 -19
Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 7e.
Steels
Low Alloy High Alloy
low carbon
<0.25wt%C
Med carbon
0.25-0.6wt%C
high carbon
0.6-1.4wt%C
Uses auto
struc.
sheet
bridges
towers
press.
vessels
crank
shafts
bolts
hammers
blades
pistons
gears
wear
applic.
wear
applic.
drills
saws
dies
high T
applic.
turbines
furnaces
V. corros.
resistant
Example 1010 4310 1040 4340 1095 4190 304
Additions none
Cr,V
Ni, Mo
none
Cr, Ni
Mo
none
Cr, V,
Mo, W
Cr, Ni, Mo
plain HSLA plain
heat
treatable
plain tool
austenitic
stainless
Name
Hardenability 0 + + ++ ++ +++ 0
TS - 0 + ++ + ++ 0
EL + + 0 - - -- ++
increasing strength, cost, decreasing ductility
Chapter 11 -20
Ferrous Alloys
Iron containing – Steels - cast irons
Nomenclature AISI & SAE
10xx Plain Carbon Steels
11xx Plain Carbon Steels (resulfurized for machinability)
15xx Mn (10 ~ 20%)
40xx Mo (0.20 ~ 0.30%)
43xx Ni (1.65 - 2.00%), Cr (0.4 - 0.90%), Mo (0.2 - 0.3%)
44xx Mo (0.5%)
where xx is wt% C x 100
example: 1060 steel – plain carbon steel with 0.60 wt% C
Stainless Steel -- >11% Cr

11. 11
Chapter 11 -21
Cast Iron
• Ferrous alloys with > 2.1 wt% C
– more commonly 3 - 4.5 wt%C
• low melting (also brittle) so easiest to cast
• Cementite decomposes to ferrite + graphite
Fe3C 3 Fe (a) + C (graphite)
– cementite (Fe3C) a metastable phase
– graphite formation promoted by
• Si > 1 wt%
• slow cooling
Chapter 11 -22
Fe-C True Equilibrium Diagram
Graphite formation
promoted by
• Si > 1 wt%
• slow cooling
1600
1400
1200
1000
800
600
400
0 1 2 3 4 90
L
g+L
a + Graphite
Liquid +
Graphite
(Fe) Co, wt% C
0.65
740°C
T(°C)
g+ Graphite
100
1153°Cg
Austenite 4.2 wt% C
a + g
Cast iron
1. Gray iron
2. Nodular (ductile) iron
3. White iron
4. Malleable iron
5. Compacted graphite iron
(CGI)

12. 12
Chapter 11 -23
Types of Cast Iron
Gray iron
– 1 - 3 % Si, 2.5 – 4% C
– graphite flakes plus ferrite/pearlite
– brittleness due to the flake-like graphite
• weak & brittle under tension
• stronger under compression
• excellent vibrational dampening
• wear resistant
Ductile (nodular) iron
– a small amount (0.05 wt%) of Mg or Ce
– spheroidal graphite precipitates (nodules)
rather than flakes
– matrix often pearlite or ferrite
– Ductility increased by a factor of 20, strength
is doubled
Chapter 11 -24
Optical micrograph of a grey
iron (Fe-3.3C-2.1Si-0.5Cr-
0.5Mo-1.0Cu)
Microstructure of pearlite in
the grey iron (Fe-3.3C-2.1Si-
0.5Cr-0.5Mo-1.0Cu). TEM.

13. 13
Chapter 11 -25
(a) steel; (b) grey cast iron
Chapter 11 -26
Types of Cast Iron
White iron
– <1wt% Si, harder but brittle
– eutectic carbide plus pearlite
– large amount of Fe3C formed during
casting
Malleable iron
– the result of annealing white iron
castings, 800º-900º C
– cementite→ graphite precipitates,
clusters or rosettes
– more ductile

14. 14
Chapter 11 -27
Types of Cast Iron
Compacted graphite iron (CGI)
1. C: 3.1-4.0%, Si: 1.7-3.0%
2. Lower content of Mg or Ce
3. Worm-like (vermicular)
graphite particles
• higher thermal conductivity
• better resistance to thermal shock
• lower oxidation at elevated
temperature
Chapter 11 -28
Production of Cast Iron
Adapted from Fig.11.5,
Callister 7e.

15. 15
Chapter 11 -29
Cast iron
Chapter 11 -30
Which type of cast iron is in the pictures illustrated below ?

16. 16
Chapter 11 -31
Limitations of Ferrous Alloys
1) Relatively high density
2) Relatively low conductivity
3) Poor corrosion resistance
Chapter 11 -32
Metal Fabrication
• How do we fabricate metals?
– Blacksmith - hammer (forged)
– Molding - cast
• Forming Operations
– Rough stock formed to final shape
Hot working vs. Cold working
• T high enough for • well below Tm
recrystallization • work hardening
• Larger deformations • smaller deformations

17. 17
Chapter 11 -33
FORMING
roll
Ao
Ad
roll
• Rolling (Hot or Cold Rolling)
(I-beams, rails, sheet & plate)
Ao Ad
force
die
blank
force
• Forging (Hammering; Stamping)
(wrenches, crankshafts)
often at
elev. T
Adapted from
Fig. 11.8,
Callister 7e.
Metal Fabrication Methods - I
ram billet
container
container
force
die holder
die
Ao
Adextrusion
• Extrusion
(rods, tubing)
ductile metals, e.g. Cu, Al (hot)
tensile
force
Ao
Addie
die
• Drawing
(rods, wire, tubing)
die must be well lubricated & clean
CASTING JOINING
Chapter 11 -34
FORMING CASTING JOINING
Metal Fabrication Methods - II
• Casting- mold is filled with metal
– metal melted in furnace, perhaps alloying
elements added. Then cast in a mold
– most common, cheapest method
– gives good production of shapes
– weaker products, internal defects
– good option for brittle materials

18. 18
Chapter 11 -35
• Sand Casting
(large parts, e.g.,
auto engine blocks)
Metal Fabrication Methods - II
• trying to hold something that is hot
• what will withstand >1600ºC?
• cheap - easy to mold => sand!!!
• pack sand around form (pattern) of
desired shape
Sand Sand
molten metal
FORMING CASTING JOINING
Chapter 11 -36
plaster
die formed
around wax
prototype
• Sand Casting
(large parts, e.g.,
auto engine blocks)
• Investment Casting
(low volume, complex shapes
e.g., jewelry, turbine blades)
Metal Fabrication Methods - II
Investment Casting
• pattern is made from paraffin.
• mold made by encasing in
plaster of paris
• melt the wax & the hollow mold
is left
• pour in metal
wax
FORMING CASTING JOINING
Sand Sand
molten metal

19. 19
Chapter 11 -37
plaster
die formed
around wax
prototype
• Sand Casting
(large parts, e.g.,
auto engine blocks)
• Investment Casting
(low volume, complex shapes
e.g., jewelry, turbine blades)
Metal Fabrication Methods - II
wax
• Die Casting
(high volume, low T alloys)
• Continuous Casting
(simple slab shapes)
molten
solidified
FORMING CASTING JOINING
Sand Sand
molten metal
Chapter 11 -38
CASTING JOINING
Metal Fabrication Methods - III
• Powder Metallurgy
(materials w/low ductility)
pressure
heat
point contact
at low T
densification
by diffusion at
higher T
area
contact
densify
• Welding
(when one large part is
impractical)
• Heat affected zone:
(region in which the
microstructure has been
changed).
Adapted from Fig.
11.9, Callister 7e.
(Fig. 11.9 from Iron
Castings
Handbook, C.F.
Walton and T.J.
Opar (Ed.), 1981.)
piece 1 piece 2
fused base metal
filler metal (melted)
base metal (melted)
unaffectedunaffected
heat affected zone
FORMING

20. 20
Chapter 11 -39
Annealing: Heat to Tanneal, then cool slowly.
Based on discussion in Section 11.7, Callister 7e.
Thermal Processing of Metals
Types of
Annealing
• Process Anneal:
Negate effect of
cold working by
(recovery/
recrystallization)
• Stress Relief: Reduce
stress caused by:
-plastic deformation
-nonuniform cooling
-phase transform.
• Normalize (steels):
Deform steel with large
grains, then normalize
to make grains small.
• Full Anneal (steels):
Make soft steels for
good forming by heating
to get g, then cool in
furnace to get coarse P.
• Spheroidize (steels):
Make very soft steels for
good machining. Heat just
below TE & hold for
15-25h.
Chapter 11 -40
a) Annealing
b) Quenching
Heat Treatments
c)
c) Tempered
Martensite
Adapted from Fig. 10.22, Callister 7e.
time (s)
10 10
3
10
5
10
-1
400
600
800
T(°C)
Austenite (stable)
200
P
B
TE
0%
100%
50%
A
A
M + A
M + A
0%
50%
90%
a)b)

21. 21
Chapter 11 -41
f11_10_pg389
Chapter 11 -42

22. 22
Chapter 11 -43
Hardenability--Steels
• Ability to form martensite
• Jominy end quench test to measure hardenability.
• Hardness versus distance from the quenched end.
Adapted from Fig. 11.11,
Callister 7e. (Fig. 11.11
adapted from A.G. Guy,
Essentials of Materials
Science, McGraw-Hill Book
Company, New York,
1978.)
Adapted from Fig. 11.12,
Callister 7e.
24°C water
specimen
(heated to g
phase field)
flat ground
Rockwell C
hardness tests
Hardness,HRC
Distance from quenched end
Chapter 11 -44
• The cooling rate varies with position.
Adapted from Fig. 11.13, Callister 7e.
(Fig. 11.13 adapted from H. Boyer (Ed.)
Atlas of Isothermal Transformation and
Cooling Transformation Diagrams,
American Society for Metals, 1977, p.
376.)
Why Hardness Changes With Position
distance from quenched end (in)
Hardness,HRC
20
40
60
0 1 2 3
600
400
200
A fi M
A
fi
P
0.1 1 10 100 1000
T(°C)
M(start)
Time (s)
0
0%
100%
M(finish)
M
artensite
M
artensite
+
Pearlite
Fine
Pearlite
Pearlite

23. 23
Chapter 11 -45
Hardenability vs Alloy Composition
• Jominy end quench
results, C = 0.4 wt% C
(table 11.2a p363)
• "Alloy Steels"
(4140, 4340, 5140, 8640)
--contain Ni, Cr, Mo
(0.2 to 2wt%)
--these elements shift
the "nose".
--martensite is easier
to form.
Adapted from Fig. 11.14, Callister 7e.
(Fig. 11.14 adapted from figure furnished
courtesy Republic Steel Corporation.)
Cooling rate (°C/s)
Hardness,HRC
20
40
60
100 20 30 40 50
Distance from quenched end (mm)
210100 3
4140
8640
5140
1040
50
80
100
%M4340
T(°C)
10
-1
10 10
3
10
50
200
400
600
800
Time (s)
M(start)
M(90%)
shift from
A to B due
to alloying
BA
TE
Chapter 11 -46
• Effect of quenching medium:
Medium
air
oil
water
Severity of Quench
low
moderate
high
Hardness
low
moderate
high
• Effect of geometry:
When surface-to-volume ratio increases:
--cooling rate increases
--hardness increases
Position
center
surface
Cooling rate
low
high
Hardness
low
high
Quenching Medium & Geometry

24. 24
Chapter 11 -47
• Steels: increase TS, Hardness (and cost) by adding
--C (low alloy steels)
--Cr, V, Ni, Mo, W (high alloy steels)
--ductility usually decreases with additions.
• Non-ferrous:
--Cu, Al, Ti, Mg, Refractory, and noble metals.
• Fabrication techniques:
--forming, casting, joining.
• Hardenability
--increases with alloy content.
• Precipitation hardening
--effective means to increase strength in
Al, Cu, and Mg alloys.
Summary