High speed steel type cold rolling mill roll by continuous pouring process for cladding

Because strip rolling work is performed through the roll, the quality of a roll which contacts a product directly influences product quality and productivity. The improvement in roll performance has been intensely needed. The authors developed the high speed steel roll manufactured by the CPC process (Continuous Pouring process for Cladding) in order to provide a fast improvement in a life of roll. The feature and the obtained result of the new roll are summarized as follows. (1) It has a fine casting microstructure with the hard eutectic carbide; (2) High hardness over 800HV, the stable structure at high temperature and low residual stress are achieved because of the application of progressive low frequency induction hardening process and high temperature tempering. As a result, the resistance to roll marks and cracking in incident is improved; (3) When rolling operation is presented, the developed roll maintains the initial surface roughness much longer and holds the stable friction coefficient within a roll bite. The rolling campaigns have been greatly improved 3 to 5 times comparing to the conventional 5 mass% chromium forged steel roll; and (4) Wear loss of a roll is also very small and the width inversion (schedule-free) operation in using oil lubricants is attained. Thus, this roll demonstrates a high performance in wear resistance, small fall of surface roughness, and the resistance to incident, and eases the restrictions conditions of a roll reason sharply in a cold rolling field. In addition to the improvement in productivity, a flexible rolling operation, the simplification and laborsaving of roll management, and the increase in efficiency of a physical distribution are expected.