Q390B

Alloy Steel

Q390B

Low-alloy high-strength structural steel. (GB/T 1591; equiv GB Q345 / EN S355 / ASTM A572 Gr50). Nominal values—confirm mill certificate.

Chemical Composition (%)

C0.2
MN1.7
SI0.55
P0.035
S0.035

Mechanical Properties

Tensile:470-630 MPa;Yield:≥345 MPa

Chinese Standard

T 1591 Q390B

Equivalent Standards

GB Q345 / EN S355 / ASTM A572 Gr50

Applications

低合金高强度结构钢。,"Plate

Available Forms

Section"

Uses

Carburizing (case-hardening) steel with low carbon core for toughness and a hard, wear-resistant surface after carburizing. Used for gears, camshafts, pinions, spline shafts, bushings and transmission parts subjected to fatigue and surface wear.

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. Carburize 900–930 °C, direct/intake quench, temper 150–200 °C; useful case depth 0.5–1.5 mm.

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). Machine the core stock before surface hardening; leave grinding allowance for the hardened case.

Request a Quote Back to category

Comments 0