Strength and hardenability steel more than 30 high, medium welding, cold deformation, the plastic medium, good machinability, usually used in normalizing the state, for the manufacture of bolts, nuts, leverage, and high-stress work in small parts.
     Chemical composition:
     Carbon C: 0.27 ~ 0.35
     Si Si: 0.17 ~ 0.37
     Manganese Mn: 0.70 ~ 1.00
     Sulfur S: ≤ 0.035
     Phosphorus P: ≤ 0.035
     Chromium Cr: ≤ 0.25
     Ni-Ni: ≤ 0.25
     Copper Cu: ≤ 0.25
     Mechanical properties:
     Tensile strength σb (MPa): ≥ 540 (55)
     Yield strength σs (MPa): ≥ 315 (32)
     Elongation δ5 (%): ≥ 20
     Reduction of area ψ (%): ≥ 45
     Impact energy Akv (J): ≥ 63
     Impact toughness αkv (J/cm2): ≥ 78 (8)
     Hardness: no heat treatment, ≤ 217HB; annealed steel, ≤ 187HB
     Sample Size: Sample size is 25mm
     Heat treatment and microstructure specifications:
     Heat treatment specifications: normalizing, 880 ℃; quenching, 860 ℃; tempering, 600 ℃.
     Delivery status: no heat treatment or heat treatment (annealing, normalizing or tempering) the status of delivery. Demands heat treatment delivery should be specified in the contract, not indicated by no heat treatment delivery.