連続焼鈍ライン通板材の延性に及ぼす張力とロール曲げの影響

Abstract

Unlike the steel strip annealed in the laboratory, the strip processed on continuous annealing and processing line (C.A.P.L.) contains considerable dislocation. Such dislocation, or plastic strain, is considered to deteriorate the ductility of continuously annealed material.Since the strip near the soaking furnace is softened, the effect of strip tension is considerably large. Therefore, assuming that C.A.P.L. also functions as a tension leveler, the relationship is obtained between the amount of plastic strain, which is imparted to the strip, and the strip tension with respect to roll diameters. As a result, the strip is stretched each time it passes between rolls. The experiment shows that the amount of strain imparted to the strip is proportional to the degree of deterioration in the total elongation.In order to improve the mechanical properties of continuously annealed material, it is effective to reduce strip tension and increase roll diameters. In particular, if the strip tension : σt is maintained below the certain value obtainable by the next equation, σt≤Dσe2/2hE, where D : roll diameter, σe : yield stress, h : thickness of strip and E : modulus of elasticity, there exists a condition which practically enables no-strain annealing where strain does not accumulate even when the strip passes between rolls.