Steel Industry Steel-Making-Presentation .ppt

Steel making

1. Ferrous Alloys
Jeffrey DG Venezuela
Department of Mining,
Metallurgical and Materials
Metallurgical Board Review

3. Wrought Iron
 Deformable iron
 Ductility is due to
very low carbon
content
 used to create gates
and furniture w/
intricate designs!

4. Carbon Steels
Low Carbon -
contain up to 0.30%
C; typical uses are
in automobile body
panels, tin plate,
and wire products.
Medium Carbon -
ranges from 0.30 to
0.60%C; used in tracks,
gears and high
strength structural
components

5. Carbon Steels
High Carbon- 0.60 to
1.00%C; used in cutting
tools, dies, razors,
blades, springs and high
strength wire
Ultra High
Carbon
1.25 to 2.0% C

6. Microstructures in Steel

7. AISI-SAE and UNS Designation for
Various Steels
AISI-
SAE
No.
Composition UNS
Counter
part
10xxPlain Carbon
Steels
G10xx0
11xxFree cutting, plain
carbon steel which
have been
resulfurized; low
phosphorus
G11xx0
12xxPlain carbon steel
which have been
resulfurized; high
phosphorus
Steel Nomenclature

8. ALLOY STEELS
13xxManganese (1 – 2%) G15xx0
14xxBoron
23xxNickel (3.5%)
25xxNickel (5.0%)
31xxNickel (1.25%), Cr (0.6%)
33xxNickel (3.5%), Cr (1.5%)
40xxMolybdenum (0.2 – 0.3%) G40xx0
41xxChromium (0.8% - 1.1%), Mo (0.15 – 0.25%) G41xx0
43xxNickel (1.65 – 2%), Cr (0.4 – 0.9%), Mo (0.2 – 0.3%) G43xx0
44xxMolybdenum (0.5%) G44xx0
46xxNickel (0.7 – 2%), Mo (0.15 – 0.3%) G46xx0
48xxNickel (3.25 – 3.75%), Mo (0.2 – 0.3%) G48xx0
50xxChromium (0.4%)
51xxChromium (0.70 – 1.10%) G51xx0
5xxxxChromium (1.0-1.5%), C (1.0%)
61xxChromium (0.70 – 1.10%), Vanadium (0.10%) G61xx0
81xxNickel (0.2 – 0.40%), Cr (0.3 -0.55%), Mo (0.08 – 0.15%)G81xx0
86xxNickel (0.3 – 0.70%), Cr (0.4 -0.85%), Mo (0.15 – 0.25%)G86xx0
87xxNickel (0.4 – 0.70%), Cr (0.4 -0.60%), Mo (0.20 – 0.30%)G87xx0
88xxNickel (0.55%), Cr (0.5%), Mo (0.35%)
92xxSilicon (1.8 – 2.2%) G92xx0
93xxNickel (0.25%), Cr (1.2%), Mo (0.12%)
98xxNickel (0.45%), Cr (0.4%), Mo (0.12%)

9. Low Alloy Steels
Less than 5% total alloy
content
primary function of the
alloying elements is to increase
hardenability
HSLA (High Strength Low Alloy
steel) has fine grains, low
carbon content and alloy
additions that strengthen steel
by solid-solution strengthening

10. Designations for Tool Steels:
Group Symbol Type
Water-
hardening
W
Shock-
resisting
S
Cold-work O
A
D
Oil-hardening
Medium-alloy air-
hardening
High-carbon high
chromium
Hot-work H (H1-H19,
incl.,chromium-based;
H20-H39, incl.,
tungsten-based; H40-
H59, incl.,
molybdenum-based)
High-speed T
M
Tungsten-based
Molybdenum-based
Mold P Mold steels (P1-P19,
incl.,low-carbon; P20-
P39, incl., other types)
Special-
purpose
L
F
Low-alloy
Carbon-tungsten

11. High Alloy Steels
Possess strength, wear resistance
and dimensional stability
greater than 0.6%C with total alloy
contents which range to more than
20%
Tool Steels

12. High Alloy Steels
Austenitic - obtained by addition of
nickel; best known is 18Cr-8Ni used in
cooking utensils and tableware
Ferritic- have sufficient Cr such that no
austenite forms at any temp; hardened
only by coldworking
Martensitic- Cr content is low enough
so that austenite can form at high
temp and transform to martensite;
used for stainless steel cutlery
Stainless Steels (at least 12%Cr)

14. Ferrite formers Austenite formers
Iron Nickel
Chromium Nitrogen
Molybdenum Carbon
Silicon Manganese
  Copper

15. High Alloy Steels
Nickel Steels - Invar(with 36% Ni)
exhibits low expansion; Alnico(20Ni-5Al-
12Co-Fe) is used to make powerful
magnets
Silicon Steels - contain about 0.5 to
5% Si ; used as core material in
magnetic circuits.
Austenitic Manganese Steel
“Hadfield Steel” - (1-1.3%C, 11-14%
Mn); hardens with cold working during
service; for high abrasion applications
Other Specialty Steels

16. Maraging steels
differ from conventional steels in that
they are hardened by a metallurgical
reaction that does not involve
carbon
strengthened by intermetallic
compounds such as Ni
3
Ti and Ni
3
Mo
(500°C)
have very high Ni, Co, and Mo

17. TYPES
•Gray Cast Iron
•Nodular (ductile)
Cast Iron
•White Cast Iron
and
•Malleable Cast
Iron
Cast Iron
Contain more than 2% Carbon
Carbon Effect = %C + %Si/3

18. (a) Gray Cast Iron
•weak and brittle in
tension
•effective in damping
vibrational energy (ex.
are engine blocks and
equipment base, etc)
•wear resistant and
least expensive
Cast Iron

19. (b) Ductile or Nodular
Cast Iron
•addition of magnesium
or cerium promotes the
formation of nodular
graphite
•common applications are
valves, pump bodies,
gears, etc.
Cast Iron

20. (c) White Cast Iron
•White fracture surface due
to presence of cementite
• very hard but extremely
brittle
• very limited application;
Chilled iron is better and
used for heavy duty parts
(used as rolls)
Cast Iron
  
                                               

21. (d) Malleable Cast Iron
•Product of annealing
white cast (heating at
1700 F: malleableizing)
• temper carbon in
ferrite or pearlite matrix
•connecting rods and
universal joint yokes,
transmission gears,
differential cases and
certain gears
Cast Iron

22. Review Questions
1. Wrought iron has carbon
content less than:
a)0.22% c) 2.14%
b)0.022% d) 0.76%
2.HSLA has alloy content less than
a)3% c) 9%
b)5% d) 10%

23. 3. A possible designation for steel with
purely pearlitic microstructure is:
a)4310 c) 4180
b)11120 d) 4340
4. The element which causes formation
of nodular graphite:
a)magnesium c) manganese
b)sulphur d) zinc
Review Questions

24. Review Questions
5. INVAR is an alloy of:
a) Fe and Nic) Ni and Cu
b) Co and Fed) Fe and Mo
6. Steel known for very good toughness
and hardened by the presence of non-
carbide-intermetallics:
a) tool steels c) maraging steels
b) silicon steelsd) HSLA

25. 7. Stainless Steel needs at least this
amount of chromium:
a) 5%c) 18%
b) 12%d) 15%
8. White cast iron possesses a white
fracture surface because of
a) cementite c) graphite flakes
b) pearlite d) graphite nodules
Review Questions

26. 9. Which element is not found in plain
carbon steel:
a) carbon c) silicon
b) magnesium d) phosporus
10. Cast iron used as engine blocks due to
its good damping capability
a) WCI c)malleable CI
b) nodular CI d) GCI
Review Questions

27. Iron and Steel Making
Department of Mining,
Metallurgical and Materials
Engineering

28. History of Appearance
 Meteoric Iron - came from meteorites!
 Wrought Iron - up to 14th century
 Steel - after 14th century
 Cast Iron - after 14th century

29. Source of Iron: Ores
Hematite - Fe
2O
3 - 70 percent iron
Magnetite - Fe
3
O
4
- 72 percent iron
Limonite - Fe
2O
3 + H
2O - 50 percent
to 66 percent iron
Siderite - FeCO
3
- 48 percent iron
In nature, iron (Fe) is attached to
oxygen (ore) and mixed with silica
(SiO2)

31. Iron Making
IRON MAKING
DIRECT INDIRECT
No melting
involved
Solid ore is
directly reduced
by gaseous
reactants
Melting involved
Ore is melted
and reduced in
this form
DIRECT

32. Direct Reduction Processes
 Bloomery (Old technique)
 Gas-Based DRP

Midrex (shaft furnace)

Circored (fluidized bed)
 Coal-Based DRP

SL/RN (rotary kiln)

Allis-Chalmers Controlled Atmosphere
Reactor (ACCAR)

33. Bloomery
Ore is burnt together with charcoal
with the help of blast air from bellows
 Temperature not too high!
 Product is a porous mass called
‘bloom’
product is forged to squeeze out
remaining slag

34. Direct Reduction Processes
 Gas-Based DRP
reducing gas
generated
externally from the
reduction furnace
Coal-Based DRP

reducing gas
generated from
hydrocarbons in
the reduction
furnace

35. Sponge Iron or Direct
Reduced Iron (DRI)
virgin iron source
uniform in composition, and virtually
free from tramp elements
used increasingly in electric furnace
steelmaking to dilute the
contaminants present in the scrap
used in these processes

36. Midrex Process (Gas-DRI)
charge is fed from top and hot gas
(600 to 900 C) is fed from the bottom
of furnace
charge passes thru the preheat,
reduction, and cooling zones
reducing gas: 95% H
2 + CO

38. SL/RN Process (Coal-DRI)
The charge (1800°F) usually consists
of lump ore (or pellets), coal and flux
Reduction brought about by reducing
gases generated from hydrocarbons
present in the reduction section
product collected at the bottom

39. Iron Making
IRON MAKING
DIRECT INDIRECT
No melting
involved
Solid ore is
directly reduced
by gaseous
reactants
Melting involved
Ore is melted
and reduced in
this form
DIRECT INDIRECT

40. Indirect Reduction
Processes
 The ore is heated above the melting
point of iron
 e.g. blast furnace

41. Blast Furnace

42. Parts of the Blast Furnace

43. Blast Furnace Charge
 Ore - source of iron
 Coke - fuel and reducing agent
 Limestone - flux
Placed in Alternating Layers in the Blast Furnace!

44. Recipe for Pig Iron
To create a ton of pig iron:

2 tons of ore

1 ton of coke

half-ton of limestone

5 tons of air.

The temperature reaches 1600 degrees C
at the core of the blast furnace!

45. Blast Furnace
Operation
 charge descends down the shaft
 blast of air burns coal and partially
melts ore
 ore reacts with carbon monoxide (CO)
and is reduced to iron
 lime combines with silicates to form slag
 both molten metal (‘pig iron’) and slag
is tapped at the bottom

46. HOT METAL

47. Important reactions in the
Blast Furnace
 C + O
2
 CO
2


exothermic - source of heat
 CO
2 + C  2CO

Boudouard reaction (source of reducing
agent)
 Fe
2
O
3
+ 3CO



2Fe+ 3CO
2


indirect reduction of the ore

Fe
2O
3 + 3C

2Fe+ 3CO

direct reduction of the ore

49. Steel Making Processes
Bessemer Process
Siemens Open Hearth
Oxygen Steelmaking Processes
Electric Arc Furnace

50. Stages of Refining
Primary Refining
done in the
converter
Secondary
Refining

done in a separate
station

51. Principle of Steel Making
Processes
pig iron is cleaned by
reacting oxygen(from
air) with impurities!
Done in Converters
oxides are collected in the slag
the heat of oxidation raises the
temperature of the mass and keeps it
molten during operation

52. Bessemer Converter

53. Bessemer Process
 bottom blown (air)
 capacity: 8 to 30 tons of molten iron
 main source of heat is the heat of
oxidation of impurities
 difficult to control

54. Acid or Basic Process?
Acid Bessemer
removes Mn and C
only and retains P
and S
used when P
content is low
 uses silica and
fireclay as lining
Basic Bessemer
removes Mn, C, P
and S
used when P
content is high
 uses dolomite as
lining

55. Open Hearth Process
 aka Siemens Process
 either AOH (acidic) or BOH (basic)
 furnaces have a saucer-like hearth
 capacity : 200 to 600 tons
 gas or oil fired
oxidation is achieved by addition of iron
ore (although oxygen lancing is favored)!
 Charge working : 6 to 14 hours

56. Oxygen Processes
 LD process (Linz-Donawitz)

first oxygen steelmaking process
 Basic Oxygen Furnace

American version of LD
 Kaldo Process

tilted and rotating

57. Oxygen Processes
 oxygen is delivered by
a lance
 lance maybe consumable or
nonconsumable (water cooled)
 produces large amounts of heat thus
ore and scrap maybe added as heat
sink

58. BOF Steel Converter
Exposed

59. Kaldo Process

60. BOS Process Sequence

61. Electric Arc Process
heat is generated by electric arcs struck
between carbon electrodes and the
metal bath
carbon is removed by oxygen lancing
oxidising basic slag to remove the
phosphorus
second limey slag is used to remove
sulphur and to deoxidise the metal in
the furnace.

62. Secondary Refining
any post steelmaking process
performed at a separate station prior
to casting
 standard for producing high-grade
steel
e.g. deoxidation and desulfurization
of steel

63. Secondary Refining
Functions
Desulfurization - CaO, Na
2CO
3 or CaF
2
Denitrification and dehydrogenation -
vacuum
Deoxidation - Al and Si
Decarburization- pure oxygen gas

64. Desulfurization
Stringer of MnS
Globular MnS

65. Killing Steel?
 during tapping, a large amount of
gas (oxygen) is dissolved in the steel
 dissolved O
2 reacts with C to form CO
which results to bubbling action
bubbling maybe ‘killed’ by adding Al
or Ferrosilicon (deoxidizers)

66. Rimmed, Killed and Semi-
Killed
 Rimmed Steel

no deoxidation, a rim of pure Fe occurs
 Killed Steel

completely deoxidized
 Semi-killed Steel

compromise between killed and rimmed

some dissolved oxygen

67. Capped Rimmed
Steel
Semikilled SteelKilled Steel

69. Vacuum Degassing
 ultimate technique to remove
dissolved gases such as N
2, H
2 and O
2
 exposing the melt to very low
pressures
 based on Sievert’s Law
[C
gas]
L = K[P
gas]
1/2

70. Vacuum Degassing and
Equipment
 RH (Ruhrstahl-Hausen) Type
 LF (Ladle Furnace) Type
 AOD (argon oxygen decarburization)
Furnace
 VOD (vacuum oxygen
decarburization) Furnace

72. Vacuum Degassing

73. Steel Products

74. Steel Products

75. Review Questions
1. Gas-based DRI uses this as a
reducing agent:
a)CO
2
c) H
2
O
b)N
2
d) CO
2.The product of the direct reduction
process is called:
a)pig iron b) sponge iron
b)meteoric irond) blooming iron

76. 3. The Midrex process is a:
a)Gas-based DRI c) Indirect process
b)Coal-based DRI d) Oxygen steelmaker
4. A steel with a cross section of 5”x5” is
called a:
a)billet c) slab
b)bloom d) ingot
Review Questions

77. Review Questions
5. Vaccum degassing is done to remove
excess:
a) carbon c) oxygen
b) manganese d) argon
6. This element is not removed in the Acid
Bessemer:
a) manganese c) phosphorus
b) carbon d) all of the above

78. 7. Stainless Steel is created in this refining
chamber:
a) Bessemerc) BOF
b) AOD d) EAF
8. The following are used as raw materials
used in the blast furnace except:
a) limestone c) limonite
b) magnetite d) coal
Review Questions

79. 9. This technique for steelmaking uses
an oxygen lance to introduce pure
oxygen into molten iron:
a) bessemer c) siemens
b) open-hearthd) basic oxygen
10. The problem with the product of
the Bessemer process is:
a) high oxygen c) high sulfur
b) high nitrogend) high phosphorus
Review Questions

80. The End