Quenching Microstructure And Mechanical Properties Of Rolled Supercooled Austenite

The quenching and tempering microstructures and the mechanical properties ofsupercooled austenite of a low-carbon Si-rich alloy which was deformed at differenttempreatures then quenched in water and tempered at different temperatures was studiedin this paper.The alloy steel was austenitized at900℃for30minutes then heated for10secondsin the salt bath furnace of370℃,400℃and430℃respectively. Then rapidly rolled ofreduction30%and rapidly cooled in water to room temperature. The steel was reheated to200,300,400and500℃in Muffle furnace for two hours. Mechanical properties such ashardness, tensile test and impact test of quenching and tempering state samples weremeasured.Results of the experiments show that lath martensite structure was obtained by thedeformation of the supercooled austenite and martensite has a preferred orientation byrolling deformation of the supercooled austenite and smaller angle of the martensitic lathwas obtained. The lathe size was from157±19nm to104±15nm by the deformation. Withthe increase of tempering temperature, the martensite lath size decreased.The hardness of the quenching state from rolled supercooled austenite is increasedobviously. While there is little difference about the hardness with the differ rollingtemperature. As the tempering temperature increased slowly, the hardness will decreased.A large number of dislocations are introduced and refinement of martensite lath size isachieved with the rolling process. The impact toughness, tensile strength and yieldstrength of warm-rolled steels all were improved. The improvement of the yield strengthwas the biggest. The yield strength was first increased then decreased following theincreased tempering temperature, while the tensile strength was decreased. Theimprovement of the strength by rolling deformation was not obvioused when thetempering temperature was at400℃.