Mitsubishi Materials Corporation

Kimura Chuzosho Co., Ltd.

Kouichi Mabuchi

Toshitake Kanno

Jun Iwahashi

Noriyuki Kakehashi

Noriaki Miwa

Naoshi Yamashita

A combined roll is provided which offers excellent resistance to thermal shock. In this combined roll, an external ring portion is formed of a cemented carbide, and an internal ring portion is formed of a ductile iron metallurgically bonded to the external ring portion by means of casting. The external ring portion is formed of a cemented carbide containing, as binder phase-defining components, Co: 5-27%, Ni: 2-12% and Cr: 0.3-3% and WC as substantially all of the balance and as a hard phase-defining component. The internal ring portion is formed of a ductile iron composed of C: 3 4.5%, Si: 1.5-4.5%, Mn: 0.1-2% and Mg: 0.02-0.2% and, as the balance, Fe and incidental impurities. The internal ring portion may also contain 0.1-5% of one or more of Mo, Cu, Cr, V, W, Sn and Sb. The internal ring portion contains a cored spheroidal graphite structure dispersed in a mixed phase of either perlite, beinite and martensite phases with a ferrite phase. The cored spheroidal graphite structure has a spheroidal graphite core formed during casting and a periphery deposited around the core during thermal treatment.

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Gifu-ken, Japan

Kouichi Mabuchi