Chemical composition
Carbon C: 0.47 ~ 0.55
Si Si: ≤ 0.40
Manganese Mn: 0.70 ~ 1.10
Sulfur S: ≤ 0.030
Phosphorus P: ≤ 0.030
Chromium Cr: 0.90 ~ 1.20
Ni-Ni: ≤ 0.35
Copper Cu: ≤ 0.25
Vanadium V: 0.10 ~ 0.25
Mechanical properties
Tensile strength σb (MPa): ≥ 1274 (130)
Yield strength σs (MPa): ≥ 1127 (115)
Elongation δ5 (%): ≥ 10
Reduction of area ψ (%): ≥ 40
Hardness: hot, ≤ 321HB; cold-drawn + heat treatment, ≤ 321HB
Standard heat treatment and microstructure
Standard heat treatment: quenching 850 ℃ ± 20 ℃, oil cooling; tempering 500 ℃ ± 50 ℃ (special needs, ± 30 ℃).
● Delivery status: hot-rolled steel to heat treatment or heat treatment delivery, cold-drawn steel with heat treatment delivery.