Patent ID: 6136110
Filing Date: 2000-10-24
Classification: C22C

Abstract:
A process for producing a ferritic heat-resistant steel comprising:providing a steel having a composition comprising, in terms of weight percent,C: 0.05 to 0.15%,Mn: more than 0.50 to 1.5%,Mo: 0.10 to 1.15%,Nb: 0.005 to 0.05%,Si: 0.10 to 0.80%,Cr: 0.5 to 1.5%,V: 0.005 to 0.30%,B: 0.0002 to 0.0050%,and the balance of Fe and unavoidable impurities;softening said steel by the steps of first normalizing said steel at a temperature within the range of 950 to 1,010.degree. C.; and immediately after said normalizing, carrying out tempering while keeping a T.P. value, expressed by the following formula, within the range of 18.50.times.10.sup.3 to 20.90.times.10.sup.3 :T.P.=T(20+log t)whereT: tempering temperature (K),t: tempering time (hr);thereby providing said steel with a structure comprising not greater than 15% by area of pro-eutectoid ferrite and the balance of bainite.