HIGH-STRENGTH STEEL HAVING SUPERIOR CORROSION RESISTANCE AND FATIGUE CHARACTERISTICS FOR SPRING, AND MANUFACTURING METHOD THEREFOR

摘要

PPROBLEM TO BE SOLVED: To provide a high-strength steel for a spring, which is manufactured by using mainly scrap for a raw material, and has superior corrosion resistance and fatigue characteristics; and a manufacturing method therefor. PSOLUTION: This high-strength steel comprises, by mass%, 0.45-0.7% C, 0.15-2.5% Si, 0.3-1% Mn, 0.015% or less P, 0.015% or less S, 0.3-2% Cu, 0.01-0.1% sol.Al, 0.1% to less than 0.5% Cr, 0.005-0.1% Ti, 0.1% or less Sn+Sb+As while satisfying (Sn+Sb+As)/Cu 0.05, one or more elements among Ni, Mo, V and Nb while satisfying Ceq 0.90%, and the balance iron with unavoidable impurities. The manufacturing method comprises: heating the above steel at such a temperature as to satisfy 950TT', wherein T'=1083-ä1509*(([%Sn]+[%Sb]+[%As])/[%Cu])SP2/SP+535*(([%Sn]+[%Sb]+[%As])/[%Cu])}, while [%Sn], [%Sb], [%As] and [%Cu] represent mass%; hot-rolling it; and then quenching and tempering it. PCOPYRIGHT: (C)2006,JPO&NCIPI