25MnB

Alloy Steel

25MnB

Chinese GB steel grade 25MnB

Chemical Composition (%)

C0.23
SI0.17
MN1
CR0.3
TI0.04
B0.0005
P0.035
S0.035

Applications

Chinese national standard (GB) steel grade per GB/T specification.

Available Forms

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

Uses

Low-alloy engineering steel with enhanced hardenability and strength from alloying elements. Chromium (≈0.45%) improves hardenability, wear and corrosion resistance. Applied to gears, shafts, bolts, connecting rods, pressure parts and heavy forgings in automotive, energy and machinery sectors.

Heat Treatment

Typically normalized (880–920 °C, air cool) or carburized (900–930 °C) for case-hardening grades, then quenched and tempered at 150–200 °C.

Precautions

Weldable with standard procedures; preheat may be needed for thick sections or higher-carbon/ alloy grades. Protect from decarburization during heating (controlled atmosphere or protective coating).

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