HEAT TREATMENT OF FE BASE HEAT RESISTING ALLOY SUPERIOR IN CREEP RUPTURE PROPERTY

摘要

PURPOSE:To obtain Fe base heat resisting alloy superior in smooth creep strength, etc., by hot forging ingot of Fe base heat resisting alloy having a prescribed component compsn., then applying solid soln. heat treatment by homogenization holding, next the first step ageing treatment, then the second step ageing treatment from temp. higher than previously described temp. CONSTITUTION:Steel ingot of Fe base heat resisting alloy composed of, by weight % 0.002-0.12 C, =1.0 Si, =2 Mn, 12-18 Cr, 20-35 Ni, 1-2 Mo, 1.2-3.0 Ti, =1 Al, 0.001-0.015 B, 0.1-1 V and the balance Fe with inevitable impurity is hot forged. Next, the steel is soaked at 890-1,100 deg.C and solid soln. heat treated, then soaked at 650-720 deg.C for 5-35hr. Next, the steel is subjected to the second step ageing treatment in which it is heated to temp. higher than the soaking temp. by 20 deg.C, soaked for 5-35hr, then cooled, to obtain Fe base heat resisting forging alloy having previously described characteristics and superior in notch creep strength and rupture elongation.