PREPARATION OF HIGH STRENGTH AUSTENITE STAINLESS STEEL EXCELLENT IN GRAIN BOUNDARY CORROSION RESISTANCE AND GRAIN BOUNDARY STRESS CORROSION CRACKING RESISTANCE

摘要

PURPOSE:To prepare a pipe excellent in grain boundary corrosion resistance and grain boundary stress corrosion cracking resistance, by applying cold processing to austenite stainless steel under a predetermined draft and, thereafter, applying heat treatment and final cold processing thereto under a specific conditions. CONSTITUTION:In preparing a pipe from austenite stainless steel, cold processing is applied to said stainless steel under a draft of at least 45% to mold a pipe which is, in turn, subjected to ageing heat treatment at 700 deg.C+t deg.C (t is 0-100 deg.C), that is, 700-800 deg.C. When the thickness of the pipe is 1mm., a heat treatment time is set to 10min or more at the time of t=0-50 deg.C and 5min or more at the time of t=50-100 deg.C. Next, softening annealing treatment is performed at 900- 1,050 deg.C for such a predetermined time that no grain boundary corrosion nor grain boundary stress cracking sensitivity appears after said annealing treatment and the succeeding final cold processing under a processing ratio of 15% or less and, after quenching, cold processing is succeedingly applied to the treated pipe under a processing ratio of 15% or less to finish the same.