● Features and application: to highlight the advantages of good hardenability, while thermal processing properties, mechanical properties, good resistance to decarburization performance is also a large section of a variety of important springs, such as cars, motorcycles large spring, spiral spring. SUP9 spring steel with high strength, ductility and toughness, good hardenability, heat-sensitive than the low-manganese, silico-manganese steel decarburization tendency than the small, temper brittleness. SUP9 spring steel used for cars, tractors and industrial production of heavy load, stress and a larger spring diameter larger coil spring. ● Chemical Composition: C: 0.52 ~ 0.60 Si Si: 0.17 ~ 0.37 Mn Mn: 0.65 ~ 0.95 Sulfur S: ≤ 0.030 P P: ≤ 0.030 Chromium Cr: 0.65 ~ 0.95 Ni Ni: ≤ 0.35 Copper Cu: ≤ 0.25 V V : 0.10 ~ 0.20 [1] ● mechanical Properties: tensile strength σb (MPa): ≥ 1225 (125) conditions yield strength σ0.2 (MPa): ≥ 1080 (110) elongation δ5 (%): ≥ 9 (for reference) cross-section shrinkage ψ (%): ≥ 20 hardness: hot, ≤ 321HB; cold-drawn + heat treatment, ≤ 321HB