抄録
The quality of work rolls that come into direct contact with the steel product has a direct effect on product quality and mill operation. A forged steel with a chromium content of 5 mass% has been conventionally used to meet the requirement of metallurgical structure homogeneity and high hardness for work rolls in cold rolling. Rolls having improved performance are strongly demanded. The authors develop the rolls of high speed steel type by using a continuous pouring process for cladding (CPC process). The characteristics and benefits of the new rolls are summarized as follows. (1) Precipitated hard carbides are utilized to attain a fine cast structure. (2) Low-frequency progressive induction hardening and high-temperature tempering are employed to provide a high hardness of HV 800 or more, a stable structure at elevated temperatures and low residual stress. As a result, the new rolls are improved in dent resistance and crack resistance. (3) When used in rolling operation, the new rolls retain a stable friction coefficient in the roll bite and allow continuous rolling of a large tonnage since their surface roughness decrease is small. (4) The wear of the new rolls is extremely small. A schedule-free rolling operation can be done when the work rolls are lubricated with rolling oil. In this way, high speed steel rolls manufactured by the CPC process exhibit high wear resistance, surface roughness retentivity and crack resistance.
