AISI 4140 Steel Round Bar Sheet Plate, JIS SCM440, DIN 1.7225
AISI 4140 alloy steel round bar sheet plate has high fatigue strength and low notch sensitivity. Low-temperature impact toughness is also very high, no obvious temper brittleness. It is mainly used after quenching and tempering state. It is used to manufacture high-strength parts under impact loads and the fittings with large cross-sections and other stressed members. Such as the horizontal eccentric shaft of the horizontal forging machine, the crankshaft of the forging press, and etc. And the equivalent grade for it is DIN 1.7225 and JIS SCM440. 4140 Steel properties and chemical composition as below.
4140 Steel Mechanical Properties
| Properties | Metric | Imperial |
|---|---|---|
| Tensile strength | ＞1080 MPa | ＞156640 psi |
| Yield strength | ＞930 MPa | ＞134890 psi |
| Elongation at break | ＞12% | ＞12% |
| Reduction of area | ＞45% | ＞45% |
| Hardness | ≤217HB | ≤217HB |
Chemical Composition
The following table shows the chemical composition of AISI 4140 alloy steel.
| Element | Content (%) |
|---|---|
| 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 |
| Iron, Fe | Balance |
Physical Properties
The physical properties of AISI 4140 alloy steel are highlighted in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 7.85 g/cm3 | 0.284 lb/in³ |
| Melting point | 1416°C | 2580°F |
Mechanical Properties
The following table outlines the mechanical properties of AISI 4140 alloy steel.
| Properties | Metric | Imperial |
|---|---|---|
| Tensile strength | 655 MPa | 95000 psi |
| Yield strength | 415 MPa | 60200 psi |
| Bulk modulus (typical for steel) | 140 GPa | 20300 ksi |
| Shear modulus (typical for steel) | 80 GPa | 11600 ksi |
| Elastic modulus | 190-210 GPa | 27557-30458 ksi |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Elongation at break (in 50 mm) | 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 |
| Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only) | 13 | 13 |
| 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 coefficient (@ 0-100°C/32-212°F) | 12.2 µm/m°C | 6.78 µin/in°F |
| Thermal conductivity (@ 100°C) | 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
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.
Heat Treatment
AISI 4140 alloy steel is heated at 845°C (1550°F) followed by quenching in oil. Before hardening, it can be normalized by heating it 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 a lower tempering temperature. For example, a tensile strength of 225 ksi can be achieved by tempering at 316°C (600°F), and 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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