Patent ID: 9540704
Date: 2017-01-10
CPC Classifications: C21D,C22C

Claim:
1. A method for producing a high fatigue life quenched/tempered steel pipe, comprising quenching treatment: of keeping an unquenched starting steel pipe having a composition that comprises, % by mass, C: 0.1 to 0.4%, Si: 0.65 to 1.5%, Mn: 0.3 to 2%, P: at most 0.02% S: at most 0.01%, Cr: 0.1 to 2%, Ti: 0.01 to 0.1%, Nb: 0.01 to 0.1%, Al: at most 0.1% B: 0.0005 to 0.01%, and N: at most 0.01%, with a balance of Fe and inevitable impurities, at 900 to 1100° C. for 10 to 60 seconds and then cooling the pipe such that the pipe undergoes martensitic transformation, followed by tempering treatment of keeping it at 280 to 380° C. for 10 to 60 minutes.