STEEL FOR SPRING HAVING EXCELLENT PERMANENT SET RESISTANCE, STEEL WIRE FOR SPRING AND SPRING

摘要

PROBLEM TO BE SOLVED: To provide steel for a spring which enables the production of a spring exhibiting permanent set resistance in fatigue capable of sufficiently corresponding to required characteristics in recent years even when used in a high stress load condition as wire-drawn, a steel wire rod for a spring to be made into the stock for a spring, a spring which exhibits the above characteristics or the like. SOLUTION: The steel has a composition containing 0.5 to <0.8% C, 1.2 to 2.5% Si, 0.5 to 1.5% Mn, 0.05 to 1.5% Cr and 0.05 to 0.25% V. In ferrite in the pearlitic structure, the carbides and carbonitrides of V and Cr and the multiple carbides and multiple carbonitrides of V and Cr of <=50 nm are present by >=10 pieces/μm2 in total.