Standard: JIS G4401 SK5 Spring Steel sk5 spring steel spring steel rod sk5 Features and Scope: after quenching and tempering has high hardness and wear resistance, but low thermal rigid, poor hardenability, deformation, plasticity and low intensity . As a need to have a high hardness and wear resistance of a variety of tools, such as a simple mold and shape punch, metal cutting tools, drilling tools, woodworking cutters, cutters, axes, chisels, hand saws vertical and fitter assembly tools, dies and other minor rivet tool. Chemical Composition: Carbon C: 0.80 ~ 0.90 Si Si :0.10-0 .35 Mn Mn :0.10-0 .50 Sulfur S: ≤ 0.030 Phosphorus P: ≤ 0.030 Chromium Cr: ≤ 0.25 Copper Cu: ≤ 0.20 Note: Cr + Ni + Cu ≤ 0.40 Mechanical Properties: Tensile strength σb (MPa): ≥ 1127 (115) Yield strength σs (MPa): ≥ 980 (100) Elongation δ10 (%): ≥ 6 section shrinkage ψ (%): ≥ 30 Hardness: annealing, ≤ 187HB, indentation diameter ≥ 4.40mm; quenching, ≥ 62HRC Heat treatment and microstructure specifications: Heat treatment specifications: Sample quenching 780 ~ 820 ℃, water-cooled.