Effects of C and Mn Contents and Heating Rate on Recrystallization Texture of Al-killed Sheet Steels

Abstract

Al-killed steels containing various amounts of C (6 to 580 ppm) with two levels of Mn, and extra-low C, high Al and N steels containing various amounts of Mn (0.15 to 0.78%) were cold rolled and annealed at a heating rate between 20°C/h and 50°C/s for the investigation of recrystallization textures. The following conclusions were obtained:
(1) When steels were annealed at a slow heating rate, there existed an optimum C content which resulted in a large elongated grain structure and weak {110} and {100} and strong {111} texture components after recrystallization. The optimum C content shifted to a lower level with increasing heating rate, and was thought to be related to the optimum heating rate.
(2) The optimum heating rate for obtaining large elongated grains became higher with decreasing C content. Two new empirical formulas, dependent on the Mn content, relating the optimum heating rate with the chemical compositions of C, Mn, Al and N were proposed. These formulas can also be applicable to the case of rapid heating, such as for continuous annealing.
(3) Under the optimum heating condition, the large elongated recrystallized grain structure was always accompanied by weak {100} texture component but that was not always accompanied by weak {110} and strong {111} texture components. Therefore the essential role of AlN precipitates during heating at the optimum rate is to inhibit the recrystallization of {100} deformed matrices.