Features :High-strength carbon-carbon structure in the steel, after quenching with high strength and hardness, the machinability of steel medium, cold plastic deformation is low, poor welding, heat treatment, no temper brittleness, but lower hardenability, the critical diameter of the water to 13 * 30mm, and the tendency to crack when water quenching. This steel is usually normalizing or quenching and tempering, or high-frequency surface hardening heat treatment before use.

Chemical composition
(Mass fraction,%) C 0.47 ~ 0.55, Si 0.17 ~ 0.37, Mn 0.50 ~ 0.80, P ≤ 0.035, S ≤ 0.035, Ni ≤ 0.30, Cr ≤ 0.15, Cu ≤ 0.25,

Mechanical Properties:
Tensile strength σb (MPa): ≥ 630 (64)
Yield strength σs (MPa): ≥ 375 (38)
Elongation δ5 (%): ≥ 14
Reduction of area ψ (%): ≥ 40
Impact energy Akv (J): ≥ 31 (4)
Impact toughness αkv (J/cm2): ≥ 39 (4)
Hardness: no heat treatment, ≤ 241HB; annealed steel, ≤ 207HB
Sample Size: Sample size is 25mm.