Abstract: The present invention provides a method of manufacturing a steel product, comprising the step of heat treating a steel product having been subjected to quenching or accelerated cooling on a hot rolling line after hot rolling to pass the steel product through a plurality of induction heating apparatuses, which are installed on the hot rolling line, three times or more. The method of the present invention makes it possible to uniformly heat treat the steel product with high productivity.

Abstract: The heat-treatment apparatus for steel plate has a plurality of transfer rolls for transferring steel plate in the horizontal direction and at least one induction-heating unit for heating the steel plate. The induction-heating unit is positioned between specified adjacent transfer rolls. At least an induction-heating unit located at the most upstream side among the induction-heating units is provided with at least one pressing roll at outlet thereof to press the steel plate from above. At least the pressing roll located at the most upstream side among the pressing rolls is positioned above and facing the transfer roll located at outlet of the induction-heating unit. Owing to the heat-treatment apparatus for the steel plate, desired heat treatment can be given to the steel plate even with the induction-heating unit without adversely affecting the travel of the steel plate.

Abstract: The present invention provides a method of manufacturing a steel product, comprising the step of heat treating a steel product having been subjected to quenching or accelerated cooling on a hot rolling line after hot rolling to pass the steel product through a plurality of induction heating apparatuses, which are installed on the hot rolling line, three times or more. The method of the present invention makes it possible to uniformly heat treat the steel product with high productivity.

Abstract: A heat treatment apparatus includes a plurality of induction heating devices which heat a steel product, a correctional device which corrects the steel product, a computing device which computes supply predetermined electric power which is supplied to the induction heating device, on the basis of a size of the steel product, a conveying speed of the steel product, a heating target temperature of the steel product, and a predetermined temperature of the steel product at the previous stage of the induction heating devices, and a power supply unit which supplies the supply predetermined electric power computed by the computing device to the induction heating devices, and the computing device which computes electric power for uniform heating processing on the steel product or electric power for surface layer heating processing on the steel product.

Abstract: A heat treatment apparatus includes a plurality of induction heating devices which heat a steel product, a correctional device which corrects the steel product, a computing device which computes supply predetermined electric power which is supplied to the induction heating device, on the basis of a size of the steel product, a conveying speed of the steel product, a heating target temperature of the steel product, and a predetermined temperature of the steel product at the previous stage of the induction heating devices, and a power supply unit which supplies the supply predetermined electric power computed by the computing device to the induction heating devices, and the computing device which computes electric power for uniform heating processing on the steel product or electric power for surface layer heating processing on the steel product.