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Abstract

A method for manufacturing steel, by quenching and tempering a seamless pipe for use as a material of a hollow spring, where the seamless pipe including predetermined components is subjected to a heat treatment which is performed to satisfy quenching conditions (1) and tempering conditions (2),

(1) quenching conditions:26,000≤(T1+273)×(log(t1)+20)≤29,000900° C.≤T1≤1,050° C.,10 seconds≤t1≤1,800 seconds,  formula (1)where T1 is a quenching temperature (° C.), and t1 is a holding time (seconds) in a temperature range of 900° C. or higher, and(2) tempering conditions:13,000≤(T2+273)×(log(t2)+20)≤15,500T2≤550° C., andt2≤3,600 seconds,  formula (2)where T2 is a tempering temperature (° C.), and t2 is a total time (seconds) from start of heating to completion of cooling.

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