637M40

Alloy Steel

637M40

British BS 970 637M40 alloy steel for gears, shafts and high-strength parts.

Chemical Composition (%)

C0.15
MN0.6
CR0.3
MO0.1
P0.035
S0.035

Applications

International high-end steel grade for aerospace, oil & gas, defense or engineering machinery.

Available Forms

Bar, plate, sheet, tube, forgings, strip, wire, powder

Uses

Low-alloy engineering steel with enhanced hardenability and strength from alloying elements. Chromium (≈0.9%) improves hardenability, wear and corrosion resistance. Molybdenum (≈0.3%) raises high-temperature strength and prevents temper embrittlement. Applied to gears, shafts, bolts, connecting rods, pressure parts and heavy forgings in automotive, energy and machinery sectors.

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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