Transcript Document 7314137

STEELS AND CAST IRONS
STEELS
Fe-Fe3C Phase Diagram
STEELS
Steel Alloys can be divided into five groups
1- Carbon Steels
2- Low Alloy Steels
3- Quenched and Tempered Steels
4- Heat Treatable Low Alloy Steels
5- Chromium-Molybdenum Steels
1-Carbon Steels
10xx
Plain Carbon
11xx
Resulfurized
12xx
Resulfurized and
rephosphorized
Manganese steels
13xx
Mn 1.75
Nickel steels
23xx
Ni 3.5
25xx
Ni 5.0
51xx
Cr 0.80 – 1.05
STEELS
2-Nickel Chromium Steels
31xx
Ni 1.25 Cr 0.65-0.80
32xx
Ni 1.75 Cr 1.07
33xx
Ni 3.50 Cr 1.50-1.57
34xx
Ni 3.00 Cr 0.77
3- Chromium Molybdenum steels
41xx
Cr 0.50-0.95 Mo 0.12-0.30
6-Nickel Chromium Molybdenum
steels
43xx
Ni 1.82 Cr 0.50-0.80 Mo 0.25
47xx
Ni 1.05 Cr 0.45 Mo 0.20 – 0.35
86xx
Ni 0.55 Cr 0.50 Mo 0.20
4- Nickel Molybdenum steels
46xx
Ni 0.85-1.82 Mo 0.20
48xx
Ni 3.50 Mo 0.25
5-Chromium steels
50xx
Cr 0.27- 0.65
Alloy steel - Tool steels
AISISAE
Types
COMPOSITION %
Classification of Tools
Steels
C
Cr
V
W
Mo
Other
W1
Water hardening
0.60 -
-
-
-
-
S5
Shock resisting
0.55 -
-
-
0.40
0.80
Mn2.00 Si
O1
Oil hardening
0.90 0.50 -
0.5
-
-
A2
Cold work
1.00 5.00 -
-
1.00 -
A4
Medium
hardening
1.00 1.00 -
-
1.00 2.00 Mn
D2
Cold work High carbon
High chromium
1.50 12.0 -
-
1.00 -
M1
Cold work
0.80 4.00 1.00 1.5
8.00 -
M2
Molybdenum
0.85 4.00 2.00 6.0
5.00 -
H11
Hot work
0.35 5.00 0.40 -
1.50 -
H12
Chromium
0.35 5.00 0.40 1.5
1.50 -
P20
Die casting mold
0.35 1.25 -
0.40 -
alloy
air
-
Stainless steels
Stainless steels usually contain less than 30% Cr and more than 50% Fe. They
attain their stainless characteristics because of the formation of an
invisible and adherent chromium-rich oxide surface film. Other alloying
elements added to enhance characteristics include Ni, Mo, Cu, Ti, Al, Si,
Nb, and N. Carbon is usually present in amounts ranging from 0.03% to
1.0%. Addition of Mo improves the corrosion resistance in salt water
(316). Reduced carbon content from 0.08 wt% to 0.03 wt% further
improve corrosion resistance in chloride solutions (316L type).
Stainless steels are commonly divided into five groups:
• Martensitic stainless steels
• Ferritic stainless steels
• Austenitic stainless steels
• Duplex (ferritic-austenitic) stainless steels
• Precipitation-hardening stainless steels.
Stainless Steel Properties and Selections
Type
316
316L
Ultimate Tensile
Strength [MPa]
Yield Strength
[MPa]
Elongation
[%]
Annealed
515
205
40
Cold-finished
620
310
35
Cold-worked
860
690
12
Annealed
505
195
40
Cold-finished
605
295
34
Cold-worked
860
690
12
Condition
Corrosion resistance
Resistance to oxidation and sulfidation
 Toughness
Cryogenic strength
 Resistance to abrasion and erosion
 Resistance to galling and seizing
 Surface finish
 Magnetic properties
 Retention of cutting edge
Ambient strength
 Ductility
Elevated temperature strength
 Suitability for intended cleaning
procedures
Stability of properties in service
Thermal conductivity
 Electrical resistivity
Suitability for intended fabrication
Cast Iron
Cast Iron
Classification of Cast Iron
Cast iron has higher carbon and silicon contents than steel. The carbon
content of cast iron is 2.1 % or more. Carbon exists as free graphite in all
types of cast iron except in white cast iron (as intermetallic compound
Fe3C called cementite).
There are four basic types of cast iron:
–
1- White cast iron ( hard, brittle, and not weldable)
–
2- Grey cast iron (relatively soft, easily machined and welded. Main
applications: engine cylinder blocks, pipe, and machine tool structures
–
3- Malleable cast iron (ductile, weldable, machinable and offers good
strength and shock resistance)
–
4- Nodular or Ductile cast iron (ductile, malleable and weldable)
Cast Iron
White cast iron is very hard, brittle and non-machinable. Exhibits a white,
crystalline fracture surface because fracture occurs along the iron carbide
plates.
Hyper-eutectic white cast
iron (x 100).
Hypo-eutectic white cast
iron, (x 100)
Cast Iron
The factors mainly influencing the character of the carbon are:

The rate of cooling.

The chemical composition.

The presence of nuclei of graphite and other substances.
A high rate of cooling tends to prevent the formation of graphite, hence
maintains the iron in a hard, unmachinable condition (white C.I).
If the casting consists of varying sections then the thin ones will cool at a
much greater rate than the thick. Consequently, the slowly cooled
sections will be grey C.I and the rapidly cooled material will be chilled
White C.I.
Cast Iron

Carbon: lowers the melting-point of iron and produces more graphite.
Silicon (graphite former) it will be noted that either a high carbon and
low silicon or low carbon and high silicon content give grey iron.

Sulphur and manganese: Sulphur can exist in iron, as iron sulphide,
FeS, or manganese sulphide, MnS. The first effect of the manganese is,
therefore, to cause the formation of graphite due to its effect on the
sulphur.

Phosphorus: has a little effect on the graphite-cementite ratio; but
renders the metal very fluid.
Cast Iron
Grey cast irons usually contain 2.5 to 4% C, 1 to 3% Si, and
additions of manganese, depending on the desired
microstructure (as low as 0.1% Mn in ferritic grey irons and as
high as 1.2% in pearlitics).
For common cast iron, the main elements of the chemical
composition are carbon and silicon. The combined influence of
carbon and silicon on the structure is usually taken into account
by the carbon equivalent (CE):
CE = %C + 0.3x(%Si) + 0.33x(%P) - 0.027x(%Mn) + 0.4x(%S)
Cast Iron

Silicon and aluminum increase the graphitization potential for both the
eutectic and eutectoid transformations and increase the number of graphite
particles.

Nickel, copper, and tin increase the graphitization potential during the
eutectic transformation, but decrease it during the eutectoid transformation.

Chromium, molybdenum, tungsten, and vanadium decrease the
graphitization potential at both stages. Thus, they increase the amount of
carbides and pearlite.
Cast Iron
Combined use of cerium and magnesium followed by ferro-silicon as an
inoculent is used to produce ductile or spheroidal graphite iron.
The most important heat treatments and their purposes are:






Stress relieving - a low-temperature treatment, to reduce or relieve
internal stresses remaining after casting
Annealing - to improve ductility and toughness, to reduce hardness and to
remove carbides
Normalizing - to improve strength with some ductility
Hardening and tempering - to increase hardness or to give improved
strength and higher proof stress ratio
Austempering - to yield bainitic structures of high strength, with some
ductility and good wear resistance
Surface hardening - by induction, flame, or laser to produce a local wearresistant hard surface
Cast Iron
Malleable cast iron is a heat-treated iron-carbon alloy, which solidifies in the
as-cast condition with a graphite-free structure, i.e. the total
carbon content is present in the cementite form (Fe3C).
Malleable iron, like ductile iron, possesses considerable ductility and
toughness because of its combination of nodular graphite and
low-carbon metallic matrix. Because of the way in which
graphite is formed in malleable iron, however, the nodules are
not truly spherical as they are in ductile iron but are irregularly
shaped aggregates.
Malleable iron and ductile iron are used for some of the
applications in which ductility and toughness are important.
Alloyed Cast Iron: Modification of the micro-structure and
properties of cast iron can be brought about by:
1- The use of special melting and casting technique,
2- The addition of alloying elements, and
3- Heat-treatment, particularly of white iron.
Cast Iron
Pearlitic Irons:
(0,5-2% nickel, chromium up to 0,8% and molybdenum up to 0,6%). The
addition of tin in amounts up to 0,1% promotes a fully pearlitic matrix.
High carbon Ni-Cr-Mo cast iron is useful for resisting thermal shock in
applications such as die-casting moulds and brake-drums.
Acicular Irons:
(Carbon 2,9-3,2, nickel 1,5-2,0, molybdenum 0,3-0,6%, Copper can replace
nickel up to 1-5%). This rigid, high-strength, shock-resisting material is used for
diesel crankshafts, gears and machine columns.
Martensitic Irons:
(5-7% nickel with other elements.
Very hard irons used for resisting abrasion e.g. metal working rolls.
Austenitic Irons: Non-magnetic
(11-33% nickel but below 20% it is necessary to add about 6% copper or 6%
manganese to maintain fully austenitic structures which have a good resistance
to corrosion and heat) e.g. Ni-Resist.
STEELS SPECIFICATIONS
Chemical composition is by far the most widely used basis for
classification and/or designation of steels. The most commonly used
system of designation in the United States is that of the Society of
Automotive Engineers (SAE) and the American Iron and Steel Institute
(AISI). The Unified Numbering System (UNS) is also being used with
increasing frequency.
Numbering Systems for Metals and Alloys
1. American Iron and Steel Institute (AISI)
2. Society of Automotive Engineers (SAE)
3. American Society for Testing and Materials (ASTM)
4. American Society of Mechanical Engineers (ASME)
5. American Welding Society (AWS)
6. American National Standards Institute (ANSI)
7. Steel Founders Society of America
8. Aluminum Association
9. Copper Development Association
10. U.S. Department of Defense (Military Specifications)
11. General Accounting Office (Federal Specifications)
STEELS
The Unified Numbering System (UNS) has been developed by ASTM and
SAE and several other technical societies, trade associations, and United
States government agencies.
The UNS establishes 9 series of designations for ferrous metals and
alloys. Each UNS designation consists of a single-letter prefix followed by
five digits. In most cases the letter is suggestive of the family of metals
identified: for example, F for cast irons, T for tool steel, S for stainless
steels.
D00001-D99999
Steels with specified mechanical properties
D40450-D40900
Carbon Steels
D50400-D52101
Alloy Steels Casting
F00001-F99999
Cast irons
F 10001-F15501
Cast Iron, Gray
STEELS
F 10090-F10920
Cast Iron Welding Filler Metal
F 20000-F22400
Cast Iron, Malleable
F 22830-F26230
Cast Iron, Pearlitic Malleable
F 30000-F36200
Cast Iron, Ductile (Nodular)
F 41000-F41007
Cast Iron, Gray, Austenitic
F 43000- F43030
Cast Iron, Ductile (Nodular), Austenitic
F45000 F 45009
Cast Iron, White
F47001-F47006
Cast Iron, Corrosion
G00001-G99999
AISI and SAE carbon and alloy steels
G10050-G15900
Carbon Steel
G11080-G11510
Resulfurized Carbon Steel
G12110-G12150
Rephosphorized and Resulfurized Carbon Steel
G13300-G13450
Mn Alloy Steel
STEELS
G40120-G48200
Mo Alloy Steel, Cr-Mo Alloy Steel, Ni-Cr-Mo Alloy Steel, Ni-Mo Alloy Steel
G81150-G88220
Ni-Cr-Mo Alloy Steel
G50150-G52986
Cr Alloy Steel, Cr-B Alloy Steel
G61180-G61500
Cr-V Alloy Steel
G92540-G98500
Cr-Si Alloy Steel, Si-Mn Alloy Steel, Cr-S-Mn Alloy Steel, Ni-Cr-Mo Alloy Steel,
Ni-Cr-Mo-B Alloy Steel
H00001-H99999
AISI and SAE H-steels
H10380-H15621
H-Carbon Steel, C-Mn H-Alloy Steel, C-B H Carbon Steel, Mn H-Carbon Steel,
B- Mn H -Carbon Steel
H40270-H48200
C-Mo H-Alloy Steel, Cr-Mo H-Alloy Steel Ni-Mo H-Alloy Steel
H50401-H51601
C-Cr-B H-Alloy Steel, C-Cr H-Alloy Steel
H61180-H61500
Cr-V H-Alloy Steel
H81451-H94301
Ni-Cr-Mo H-Alloy Steel
J00001-J99999
Cast steels (except tool steels)
J01700-J05003
Carbon Steel Casting
J11442-J84090
Alloy Steel Casting
J91100-J92001
Austenitic Manganese Steel Casting, Alloy Steel Casting
STEELS
J92110-J93000
Alloy Steel Casting Precipitation Hardening, Alloy Steel Casting, Cast Cr-NiMo Stainless Steel, Cast Cr-Ni Stainless Steel, Cast Cr-Mn-Ni-Si-N Stainless
Steel
J93001-J95705
Stainless Steel Casting, Cast Cr-Ni-Mo Stainless Steel, Alloy Steel Casting,
Maraging Cast Ferritic-Austenic Stainless Steel, Duplex Alloy Steel Casting,
Alloy Steel Casting
K00001-K99999
Miscellaneous steels and ferrous alloys
K00040-K08500
Carbon Steel, Carbon Steel with Special Magnetic Properties, Steel Welding
Rod, Enameling Steel
K10614-K52440
Alloy Steel, Welding Wire, High-Strength Low-Alloy Steel
K90901-K95000
Alloy Steel, Superstrength; Ferritic Cr-Mo-V Steel; Manganese Steel,
Nonmagnetic; Ni-Co Steel Welding Wire; Iron, Electrical Heating Element
Alloy; Iron Thermostat Alloy; Martensitic Age-Hardenable Alloy; Maraging
Alloy; Fe-Co Soft Magnetic Alloy; Nickel Steel; Invar; Iron; etc.
S00001-S99999
Heat and corrosion resistant steels (stainless), valve steels, iron-base "super
alloys"
S13800-S17780
Precipitation Hardenable Cr-Ni-Al-Mo-(Cu, Ti) Stainless Steels
S20100-S39000
Austenitic Cr-Mn-Ni (Si,Mo,Cu,Al) Stainless Steel; Thermal Spray Wire;
Austenitic Cr-Mn-Ni Stainless Steel and Welding Filler Metal; Austenitic CrNi Heat Resisting Steel and Welding Filler Metal; Precipitation Hardenable
Cr-Ni-(Si, Ti, Mo, Al) Stainless Steel, etc.
STEELS
S40300-S46800
Martensitic Cr Stainless Steel; Ferritic Cr Stainless Steel with Ti or Ni or
Mo; Martensitic Cr-Ni-Mo Stainless Steel; Hardenable Cr Stainless Steel
S50100-S50500
Cr Heat Resisting Steels and Filler Metal
S63005-S65007
Valve Steel
S65150-S67956
Iron Base Super alloy
T00001-T99999
Tool steels, wrought and cast
T11301-T12015
High-Speed Tool Steels
T20810-T20843
Hot-Work Tool Steels
T30102-T 30407
Cold Work Tool Steels
T31501-S31507
Oil-Hardening Steels
T41901-T41907
Shock-Resisting Tool Steels
T51602-T51621
Mold Steels
T60601-T60602
C-W Tool Steels
T61202-T61206
Low-Alloy Tool Steels
T72301-T72305
Water Hardening Tool Steels
T74000-T75008
Cr-Steels Solid Welding Wire for Machinable Surfaces and Tool and Die
Surfaces
T90102-T91907
Cast Tool Steels