C: 0.12 ~ 0.20; Mn: 1.20 ~ 1.60; Si: 0.20 ~ 0.55; Tensile strength: 470 to 660 N / mm; yield strength: 275 to 345 N / mm; elongation: 21%. Specific values ​​of the steel according to the thickness or diameter of the above data corresponding to the thickness or diameter of the steel: 16 ~ 100mm