Steam injection methods for producing seamless steel pipe, and

The present invention provides even at 350 deg.] C has a high yield stress of the steel for steam injection. Steam injection according to the present invention having a seamless steel pipe containing, by mass%, C: 0.03 ~ 0.08%, Si: 0.05 ~ 0.5%, Mn: 1.5 ~ 3.0%, Mo: greater than 0.4 ~ 1.2%, Al: 0.005 ~ 0.100% , Ca: 0.001 ~ 0.005%, N: 0.002 ~ 0.015%, P: 0.03% or less, S: 0.01% or less, Cu: 1.5% or less and the remainder consisting of Fe and chemical impurities. Steam injection seamless steel pipe is water cooled, quenched and tempered after hot working manufacture.