Mitsubishi Heavy Industries Limited

Jong Won Lee

Tsutomu Kawamizu

Akira Kaya

Junso Fukumori

Kyung Zoon Min

Woon Yong Choi

A system and a method are disclosed for preventing scale defects during hot rolling by hot rolling equipment having a scale breaker provided at an entry side of a finishing mill line composed of a plurality of rolling mills arranged in tandem. A descaler is provided between a first stage rolling mill and a second stage rolling mill of the finishing mill line. A cooler for cooling a hot rolled steel plate is provided between the second stage rolling mill and a third stage rolling mill of the finishing mill line. A control device is provided for controlling the descaler and the cooler to be selectively driven such that neither of the descaler and the cooler is actuated, one of the descaler and the cooler is actuated, or both of the descaler and the cooler are actuated, according to rolling conditions. Thus, the hot rolled steel plate is rolled, with its oxide film thickness at an entry side of the third stage rolling mill being restricted to not more than a limiting oxide film thickness of 5 &mgr;m. Consequently, scale defects are prevented, and overcooling of the hot rolled steel plate is suppressed, to improve the quality of a product.

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Tokyo, Japan

Jong Won Lee