JPS5711706A - Rolling mill line - Google Patents

Abstract

PURPOSE: To reduce the hardness dispersion in the direction of thickness of a rolled material, by installing a light reducing rolling mill between a hot rolling mill and a cooling apparatus, in a rolling mill line operated for improving the tenacity of steel through a forcible cooling process following to a rolling pass.

CONSTITUTION: A steel billet extracted from a soaking pit is rolled to reduce its thickness by a hot rolling mill 1, and is carried into a cooling apparatus 2 through a leveler 3. A light reducing rolling mill 4, provided with a rolling roll of diameter smaller than that of the main rolling mill 1, is installed in front of the leveler 3. This rolling mill 4 gives a great strain to only the steel surface before entering the cooling apparatus, in order to promote the γ→α transformation by the distortion stress and by fining grains, for preventing generation of such a hardened structure as martensite in the steel surface during the next forcible cooling process. If the said light reducing mill 4 is installed next to the leveler 3, it is more effective because the rolling strain is released and the recrystallization and grain growth are restricted thereby.

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