Patent ID: 7857919
Filing Date: 2010-12-28
Classification: C21D,Y02P

Abstract:
1. A method of manufacturing a steel product comprising heat treating a steel product which has been subjected to quenching or accelerated cooling on a hot rolling line after hot rolling by passing the steel product at least once through a plurality of induction heating apparatuses, which are installed on the hot rolling line, wherein a number of times of passage of the steel product through the induction heating apparatuses is such that a heat treatment time becomes the shortest, the heat treatment time being determined from the number of times of passage, a transfer speed of the steel product and an amount of electric power for the induction heating apparatuses, and the heat treatment time being the time in which a surface temperature of the steel product and a thickness-wise center temperature of the steel product fall within a predetermined range, wherein a peak value of the surface temperature of the steel product is controlled so that the surface temperature does not exceed a maximum value of a predetermined temperature range, and wherein conditions in which the heat treatment time becomes the shortest are determined by the following steps: (a) determining the dimensions of the steel product and a necessary temperature rise of the steel product to be subjected to the heat treating, (b) determining the transfer speed and the amount of electric power for the induction heating apparatuses when the number of times of passage is one based on the dimensions and the necessary temperature rise of the steel product determined in step (a), (c) determining the transfer speed and the amount of electric power for the induction heating apparatuses when the number of times of passage is not less than two based on the dimensions and the necessary temperature rise of the steel product determined in step (a), (d) selecting a number of times of passage in which the heat treatment time becomes the shortest based on heat treatment times when the number of times of passage is one in step (b) and when the number of times of passage is not less than two in step (c), and (e) determining the transfer speed and the amount of electric power for the induction heating apparatuses for each passage of the number of times of passage selected in step (d).