JPS5488859A - Hot rolling method for high toughness, high strength steel materials - Google Patents

Abstract

PURPOSE: To manufacture the hot rolled steel materials whose superior strength and toughness are expectable, by settling the reducing condition for the zone where the recrystallization of austenite progresses, in the rolling schedule, correspondingly to the variable to be fixed according to the rolling mill and the thickness of billet just before the rolling reduction.

CONSTITUTION: The billet is heated and is fed to the rolling mill for starting the rolling work; in such temperature zone as the static recrystallization of austenite is finished between individual rolling reductions, the condition of at least one rolling reduction is settled above the lower limit of the draft percentage and under the upper limit of the reduction temperature, correspondingly to the variable N√(R₀/H) which is obtained from the roll radius R_o of the rolling mill, the revolutional speed N of the roll, and the thickness H of the billet before the rolling reduction. This variable is thus takne into the consideraton additionally to the draft percentage and the reduction temperature; hereby, the grain size of the recrystallized austenite after the hot rolling work can be estimated, so that the manufacture of high strength, high toughness steel materials becomes possible. This method is also applicable to the caliber rolling and universal rolling of steel shapes, steel bars, rods, etc.

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