GB1321304A - Thermo-mechanical treatment of steel - Google Patents

Abstract

1321304 Altering physical properties; making sheets EXORS OF JAMES MILLS Ltd 10 May 1971 [9 May 1970] 22521/70 Headings B3A and B3V Physical properties of pearlitic or ferritic pearlitic steel are improved by austenitizing the steel, subjecting it to a first rolling or swing- forging stage while it is in the austenitic state so as to perform a major part of the reduction in area required of the complete process, cooling the steel or allowing it to cool until transformation of the austenite to pearlite or to ferrite/pearlite has substantially been completed, and in a second rolling or swing-forging stage reducing the steel by at least a further 60% commencing at a temperature below the temperature at which phase transformation from pearlite or ferritepearleit to austenite commences but not below 500‹ C., without re-heating or equalization during rolling or swing-forging and without any substantial retransformation of the ferrite/ pearleit or pearlite to austenite. After the first stage, the steel is cooled or allowed to cool to 690-500‹ C. for the second stage, or it may be stored at ambient temperature and then reheated for the second stage working. The steel is not removed from the mill between passes during the second stage reduction of 60-85% and is austenitized before the first stage by heating to 900-1300‹ C. The steel may have a carbon content of 0À2-0À7% and include Mn, S, Ph, Si, Ni, Cr, Mo, Cu and Sn, two examples being given. Cooled rolls may be used during the second stage and the steel may be cooled between passes by a water spray. After cooling, following the first state, the steel may be discharged into a soaking or equalizing furnace for equalizing the temperature before the second stage. A conventional mill may be provided with one outlet for conventional rolling and another for rolling according to the invention, via a soaking furnace.