AISI 4140 Alloy Steel (UNS G41400)
AISI 4140 Alloy Steel (UNS G41400) Written by AZoM
Sep 7 2012
Topics Covered Introduction Chemical Composition Physical Properties Mechanical Properties Thermal Properties Other Designations Fabrication and Heat Treatment Machinability Forming Welding Heat Treatment Forging Hot Working Cold Working Annealing Tempering Hardening
Introduction Alloy steels are designated by AISI four-digit numbers. They comprise different kinds of steels having composition exceeding exceeding the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels. AISI 4140 alloy steel is chromium, molybdenum, molybdenum, manganese containing containing low alloy steel. It has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. The following datasheet gives an overview of AISI 4140 alloy steel.
Chemical Composition The following table shows the chemical composition of AISI 4140 alloy steel.
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AISI 4140 Alloy Steel (UNS G41400)
Element
Content (%)
Iron, Fe
96.785 - 97.77
Chromium, Cr
0.80 - 1.10
Manganese, Mn
0.75 - 1.0
Carbon, C
0.380 - 0.430
Silicon, Si
0.15 - 0.30
Molybdenum, Mo
0.15 - 0.25
Sulfur, S
0.040
Phosphorous, P
0.035
Physical Properties The physical properties of AISI 4140 alloy steel are highlighted in the following table. Properties Density Melting point
Metric
Imperial
7.85 g/cm3
0.284 lb/in³
1416°C
2580°F
Mechanical Properties The following table outlines the mechanical properties of AISI 4140 alloy steel. Properties Tensile strength Yield strength Bulk modulus (typical for steel) Shear modulus (typical for steel)
Metric Imperial 655 MPa 415 MPa 140 GPa
210 GPa
Poisson's ratio Elongation at break (in 50 mm)
60200 psi 20300 ksi
80 GPa11600 ksi 190-
Elastic modulus
95000 psi
0.270.30
2755730458 ksi 0.27-0.30
25.70% 25.70%
Hardness, Brinell
197
197
Hardness, Knoop (converted from Brinell hardness)
219
219
Hardness, Rockwell B (converted from Brinell hardness)
92
92
13
13
Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only) Saved from URL: http://www.azom.com/article.aspx?ArticleID=6769
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AISI 4140 Alloy Steel (UNS G41400)
Hardness, Vickers (converted from Brinell hardness)
207
207
Machinability (based on AISI 1212 as 100 machinability)
65
65
Thermal Properties The thermal properties of AISI 4140 alloy steel are given in the following table. Properties
Metric
Imperial
Thermal expansion co-efficient (@ 0-100°C/32-212°F)12.2 µm/m°C Thermal conductivity (@ 100°C)
6.78 µin/in°F
42.6 W/mK 296 BTU in/hr.ft².°F
Other Designations Other designations equivalent to AISI 4140 alloy steel are listed in the following table. AMS 6349
ASTM A193 (B7, B7M)
ASTM A506 (4140)
ASTM A752 (4140)
AMS 6381
ASTM A194 (7, 7M)
ASTM A513
ASTM A829
AMS 6382
ASTM A29 (4140)
ASTM A513 (4140)
SAE J1397 (4140)
AMS 6390
ASTM A320 (L7, L7M, L7D)
ASTM A519 (4140)
SAE J404 (4140)
AMS 6395
ASTM A322 (4140)
ASTM A646 (4140)
SAE J412 (4140)
AMS 6529
ASTM A331 (4140)
ASTM A711
Fabrication and Heat Treatment Machinability AISI 4140 alloy steel has good machinability in the annealed condition.
Forming AISI 4140 alloy steel has high ductility. It can be formed using conventional techniques in the annealed condition. It requires more pressure or force for forming because it is tougher than plain carbon steels.
Welding AISI 4140 alloy steel can be welded using all conventional techniques. However, the mechanical properties of this steel will be affected if it is welded in the heat treated condition, and post weld heat treatment should be performed.
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AISI 4140 Alloy Steel (UNS G41400)
AISI 4140 alloy steel is heated at 845°C (1550°F) followed by quenching in oil. Before hardening, it can be normalized by heating at 913°C (1675°F) for a long period of time followed by air cooling.
Forging AISI 4140 alloy steel is forged at 926 to 1205°C (1700 to 2200°F)
Hot Working AISI 4140 alloy steel can be hot worked at 816 to 1038°C (1500 to 1900°F)
Cold Working AISI 4140 alloy steel can be cold worked using conventional methods in the annealed condition.
Annealing AISI 4140 alloy steel is annealed at 872°C (1600°F) followed by slowly cooling in the furnace.
Tempering AISI 4140 alloy steel can be tempered at 205 to 649°C (400 to 1200°F) depending upon the desired hardness level. The hardness of the steel can be increased if it has lower tempering temperature. For example, tensile strength of 225 ksi cab be achieved by tempering at 316°C (600°F), and a tensile strength of 130 ksi can be achieved by tempering at 538°C (1000°F).
Hardening AISI 4140 alloy steel can be hardened by cold working, or heating and quenching.
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