Chemical composition 
 Carbon C: 0.17 ~ 0.23 
 Silicon Si: 0.17 ~ 0.37 
 Mn Mn: 0.30 ~ 0.60 
 Sulfur S: Allow the residual content of ≤ 0.035 
 Phosphorus P: Allow the residual content of ≤ 0.035 
 Chromium Cr: 1.25 ~ 1.65 
 Ni - Ni: 3.25 ~ 3.65 
 Cu: to allow the residual content of ≤ 0.030 
 Mechanical properties 
 Tensile strength σb (MPa): ≥ 1175 (120) yield strength σs (MPa): ≥ 1080 (110) elongation δ5 (%): ≥ 10 Reduction of area ψ (%): ≥ 45 impact energy Akv (J ): ≥ 63 impact toughness the value αkv (J/cm2): The hardness of ≥ 78 (8): ≤ 269HB sample size: the sample blank size of 15mm 
 Heat treatment and microstructure 
 The specification of the heat treatment: quenching: the first 880 ℃, the second 780 ℃, oil cooling; tempering 200 ° C, water-cooled, air-cooled.