Abstract
In Wakayama steel works of SMI, carbon steel and stainless steel billets are rolled by 2-stand 2-high reversing blooming mill.Ni-based alloy (57Ni-15Cr-16Mo-3W) billets have been produced by hot forging because of its high deformation resistance (from 3.5 t ingot to finished bar dia. 253 mm). Recently hot rolling of the alloy became possible. Two-heat rolling is used. The relatively low soaking temperature (1 230 °C) is applied for the first rolling to prevent a hot tear formation by a grain boundary remelting of the ingot due to segregation. After the first heat rolling, the intermediate bar is reheated at 1 250 °C to assure lower deformation resistance for the final rolling.Pass design and schedule are improved to reduce the amount of deformation at the final stages. The second bloomer housing design is modified to reduce stress concentration and to allow higher rolling load application.
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