METHOD FOR SPECIFYING SIZE OF MAXIMUM NONMETAL INCLUSION IN STEEL SLAB STAGE AND STEEL SHEET SPECIFIED IN SIZE OF MAXIMUM NONMETAL INCLUSION IN STEEL SLAB

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet ensured in the quality related to a nonmetal inclusion by rapidly and simply specifying the size of the maximum nonmetal inclusion present in a predetermined area in a steel slabe stage.

SOLUTION: In a process for manufacturing a steel slab by hot rolling or hot/cold rolling of a steel sheet, a part of a cross section cut at a right angle or almost right angle with respect to the rolling direction of the steel sheet after rolling in a process for manufacturing the steel sheet by hot rolling or hot/cold rolling of the steel slab is set to an inspection standard area and the length in the direction of the nonmetal inclusion present in an inspection reference area is microscopically observed and the size of the maximum nonmetal inclusion in the slab stage of the rolled plate is estimated from the maximum width direction length of the observed nonmetal inclusion. The size of the maximum nonmetal inclusion in the slab stage of the steel sheet is specified.

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