A study was made on fatigue layer of the backup roll surface by cyclic loading in rolling and its suitable dressing program in 4 high plate finisher mill at Keihin Plant, Nippon Kokan. An examination was also made on patterns and surface temperature of the work roll after rolling operation.
The results obtained were as follows:
1) The wear patterns of top backup roll were concave and those of bottom backup roll were almost flat.
2) The layer affected by fatigue of the backup roll surface was examined by X-ray reflection method. The affected layer of top rolls extended within 1.0mm depth from the surface, while that of bottom rolls somewhat deeper than 1.0mm. Hardness measurement of the roll surface is considered to be one of the suitable means to estimate the degree of fatigue.
3) The suitable dressing program of the plate mill backup roll is 2.0mm in dia. every time for top rolls and 2.0mm in dia. at initial 3 times and 8.0mm in dia. at 4th time for bottom roll.
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