Mechanism & Prevention Measures of Roll Spalling in Cold Rolling Process

by "Nobuharu Yasutake, Masanori Kobayashi"

Publisher - KOBE STEEL, LTD., Japan

Category - Engineering & IT

"In the cold rolling process, the spalling of work roll, explosive shattering and fragmentation of the roll, is sometimes observed after rolling operation. The spalling is attributed to an initial crack on the roll surface and its propagation during the cold rolling operation. For both safety and productivity, such spalling should be prevented. This report describes the mechanisms of the spalling and preventive measures against spalling accident. The mechanisms were investigated by inspecting the fracture of the broken roll and verifying fatigue crack growth rate with the Paris law. The mechanism of the spalling is considered as follows. First, a crack on the roll surface is initiated by the thermal stress due to a slip between the roll and the material at the emergency stop of the rolling operation. Then, the crack propagates during the rotation of the roll under the stress from rolling load. Finally, the spalling occurs during cool down after the rolling operation. The treatment method of the work roll after the emergency stop of the mill has been decided on the basis of the result of this investigation. The explosive shattering due to the spalling is prevented and the safety in the cold rolling operation is achieved."

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