Heat treatment of centrifugally cast high carbon high vanadium high speed steel mill roll

The effects of austenitising temperature and temper treatment on the microstructure, hardness and abrasive wear resistance of a high carbon high vanadium high speed steel roll of composition 2·2-2·4C, 5·5-6·5V, 4·5-5·5Cr, 14·0-16·0(W+2Mo), 1·0-1·4Ni and 1·2-1·5Nb (wt-%) were investigated by light optical microscopy, scanning electron microscopy, backscattered electron image, X-ray diffraction and hardness and wear testing. It was found that the hardness increases as the austenitising temperature increases to a maximum of 1050°C, and then begins to decrease because of the increase in retained austenite. Moreover, retained austenite begins to transform into martensite with increasing tempering temperature. The retained austenite in the quenched structure leads to the temper hardening of the rolls, which promotes improved abrasive wear resistance. The roll life of high carbon high vanadium high speed steel compound rolls austenitised at 1050-1080°C and tempered at 540-560°C increased by 400% (single groove trials) compared to high nickel-chromium white cast iron rolls when the rolls were used in a K1 mill housing of a bar mill.