● Features and application: Good mechanical properties and process performance, high hardenability, adding vanadium to steel the grain refinement, reduce heat sensitivity, increased strength and toughness, high fatigue strength, yield ratio is high, but poor welding, cold plastic deformation due to the low. Is a relatively high spring, as a large section of the important spring and high-load operating temperature <300 ℃ of the valve spring, piston spring, valve spring. ● Chemical Composition: C: 0.47 ~ 0.55 Si Si: 0.15 ~ 0.35 Mn Mn: 0.65 ~ 0.95 Sulfur S: ≤ 0.030 P P: ≤ 0.030 Chromium Cr: 0.80 ~ 1.10 Ni Ni: ≤ 0.35 Copper Cu: ≤ 0.25 V V : 0.15 ~ 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 ● heat treatment and microstructure specifications: standard heat treatment: quenching 850 ℃ ± 20 ℃, oil cooling; tempering 500 ℃ ± 50 ℃ (special needs , ± 30 ℃).