CK75 basic performance characteristics and scope of application: better hardenability, quenching in oil, the critical diameter of up to 100 ~ 150mm. For the production of very large springs, such as bulldozers Diego on a plate spring, a large ship and a large coil springs torsion springs. Carbon C: 0.56 ~ 0.64 Si Si: 0.17 ~ 0.37 Manganese Mn: 0.70 ~ 1.00 Sulfur S: ≤ 0.030 Phosphorus P: ≤ 0.030 Chromium Cr: 0.70 ~ 1.00 Ni-Ni: ≤ 0.35 Copper Cu: ≤ 0.25 Boron B: 0.0005 ~ 0.004 Mechanical Properties Tensile strength σb (MPa): ≥ 1225 (125) Conditions yield strength σ0.2 (MPa): ≥ 1078 (110) Elongation δ5 (%): ≥ 9 (for reference) section shrinkage ψ (% ): ≥ 20 [1]