40MnB
Alloy Steel40MnB
(GB/T 3077). Nominal values—confirm mill certificate.
Chemical Composition (%)
| C | 0.37 |
|---|---|
| SI | 0.17 |
| MN | 1.1 |
| B | 0.0005 |
| P | 0.035 |
| S | 0.035 |
Mechanical Properties
Tensile:≥980 MPa;Yield:≥785 MPa;Elong:≥10%;RA:≥45%;Akv:≥55 J
Chinese Standard
T 3077 40MnB
Available Forms
Bar,Plate
Uses
Medium-carbon grade for machine parts such as gears, crankshafts, axles, connecting rods, spindles and forgings that need a balance of strength, toughness and machinability. Commonly supplied as bar, plate, sheet, tube and forging.
Heat Treatment
Austenitize at 820–870 °C (oil or water quench depending on section) and temper at 400–650 °C to the required strength/toughness balance.
Precautions
Preheat and control interpass temperature when welding; post-weld heat treatment or stress relief is recommended to avoid hard-zone cracking. Use low-hydrogen electrodes. Protect from decarburization during heating (controlled atmosphere or protective coating).
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