JPS569330A - Rolling method of austenite stainless steel ingot containing mo and nb - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cracks in the surface of a slab by a method in which an austenite stainless steel slab containing Mo and Nb is hot-rolled at a slow speed and then reheated during the rolling while regulating its reduction ratio per one pass. CONSTITUTION:An austenite stainless steel slab or the like containing any one or both of 1.0- 5.0% Mo and 0.5-2.0% Nb is soaked to 1,150-1,280 deg.C and then hot-rolled, where the hot rolling is performed by using a rolling mill of a low roll circumferential speed of 80m/min or less. Also, the rolling is conducted under the following initial period-low pressure and end period-high pressure; that is, with the reduction ratio of 5% or less per one pass for its overall draft of until 20% in the case of the thickness from the initial thickness before rolling to the finished thickness, the reduction ratio of 6% or less for 20-25%, the reduction ratio of 7% or less for 35-45%, the reduction ratio of 8% or less for 45-50%, the reduction ratio of 9% or less for 50-55%, the reduction ratio of 11% or less for 55-60%, and the reduction ratio of 15% for 60% or more. Also, when the rolling temperature becomes 900-1,050 deg.C during the period when the overall reduction ratio reaches 70%, the slab is reheated once or more to 1,150-1,280 deg.C to accelerate recrystallization.