BASIC CHARACTERISTICS AND MICROSTRUCTURE OF HIGH-CARBON HIGH-SPEED STEEL ROLLS FOR HOT-ROLLING MILL

Work roll life of hot rolling mills is strongly affected by roll material. Recently, high-carbon high steel rolls have been developed to improve further work roll life. In this paper, relationship between basic characteristics of roll and microstructure in high-carbon high speed steels were investigated. After specimens with the several chemical compositions made by casting, forging, and powder process were prepared, wear test, friction test, heat crack test, flexure test were conducted. Consequently, it was revealed that basic characteristics of roll were strongly dependent upon the amount, shape, size of carbide, that is, wear resistance mainly increases with an increase in the amount of carbide, seizure resistance increases as the size of carbide is larger except at a large amount of carbide, heat crack resistance and toughness increase as the shape of carbide is the more spherical and the size of that is the smaller. Moreover, it became clear from the above results that 3.0wt%C-10.0wt%V high speed steel made by powder process is one of the most desirable roll material as has a large amount of fine spherical carbide. As a result of model rolling test, it was found that wear resistance of the above material is about five times that of high Cr cast iron.