Rolled steel material for high-strength spring and wire for high-strength spring using same

Abstract

The purpose of the present invention is to provide a rolled steel material which is for use in a high-strength spring, which exhibits excellent wire drawability even when the amount of an alloying element added is reduced, and which exhibits excellent corrosion fatigue characteristics after quenching and tempering. A rolled steel material for a high-strength spring, characterized in that: the rolled steel contains C, Si, Mn, P, S, Al, Cu and Ni; the nondiffusible hydrogen content is 0.40massppm or less; the area fraction of ferrite in terms of percentage satisfies relationship (1); and the total area fraction of bainite and martensite is 2% or less. Area fraction of ferrite<{(0.77-[C]) / 0.77-[C] / 3+0.08}*100 ... (1) wherein "[element]" represents the content of the element in terms of mass%.

Description

technical field [0001] The present invention relates to a rolled material for high-strength springs and a wire material for high-strength springs using the same. Specifically, it is a rolled material and wire material useful as a raw material of a high-strength spring used in a quenched and tempered state, especially a rolled material with excellent wire drawing workability, and wire material processing Even if the final tensile strength is high strength of 1900MPa or more, it is a high-strength spring wire material with excellent corrosion fatigue characteristics. Background technique [0002] Coil springs used in automobiles, such as valve springs and suspension springs used in engines and suspensions, are required to reduce weight and increase strength in order to reduce exhaust gas and improve fuel efficiency. In the manufacture of high-strength wire, wire drawing is performed for the purpose of improving the dimensional accuracy of the wire diameter and making the stru...

AI Technical Summary

Problems solved by technology

However, in Patent Document 3, only emphasis is placed on the drawability under special processing such as strong drawing, and no consideration is given to hydrogen embrittlement resistance after quenching and tempering, which is most important in suspension springs and the like.

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