Microstructure Evolution in an Austenitic Stainless Steel during Wire Rolling

Abstract

A wire rod block at Fagersta Stainless AB, Sweden, consists of eight pairs of rolls with consecutive round-oval-round grooves. Test bars of an austenitic stainless steel of type AISI 304L that had been preheated to 930±70°C were manually fed into the wire block. By entering a guide after one of the roll pair, the bar was led out from the block into a water-filled tube for rapid quenching. The guide was moved successively from the first to the last pair of rolls and test bars were collected after each roll pair. In order to characterize the original structure one bar was preheated and directly water quenched without rolling. The aim of this study was to characterize the microstructure evolution during the wire rod rolling using electron backscatter diffraction. The size evolution for all grains, the recrystallized grains and for the subgrains in the deformed grains has been estimated and the fraction of recrystallized grains has been determined. During the first 3 passes almost no recrystallization is observed and strain accumulates. Partial recrystallization then occurs and for the last 3 passes the recrystallization is almost complete and the texture is nearly random.