4140 hot rolled steel bar is a medium-carbon alloy steel that has a high hardenability. This grade is also widely used for forging. Hot rolled 4140 steel also has good fatigue and impact resistance after heat treating.
Standard “4140 Grade” Chemical Composition
| Carbon | 0.38-0.43 |
| Manganese | 0.75-1.00 |
| Phosphorus (max) | 0.035 |
| Sulfur (max) | 0.040 |
| Silicon | 0.15-0.35 |
| Chromium | 0.80-1.10 |
| Molybdenum | 0.15-0.25 |
Estimated Mechanical Property Ranges for “Grade 4140”
| Tensile strength (psi) | 95,000 – 105,000 |
| Yield strength (psi) | 65,000 – 75,000 |
| Elongation in 2” (%) | 20 – 30 |
| Reduction of area (%) | 35 – 45 |
| Brinell Hardness (BHN) | 200 – 230 |