PURPOSE: To produce products having good quality by charging plural pieces of temp. sensors into the vertical type induction heating furnace in the height direction of the furnace side walls in equal distance positions, measuring the surface temp. distribution of a slab and controlling heating to uniform the heating.
CONSTITUTION: Plural pieces of induction heating coils 5 are divided to plural blocks and are distributed and disposed vertically on the side walls 4 of the body 3 of the vertical type induction heating furnace and while the vertical direction of the hot slab 1 is erected in a vertical direction, the slab is imposed on a stand 2 and is charged into the furnace body 3 where the slab is heated. The furnace side walls 4 are constituted of refractory bricks 4a and refractory heat insulating materials 4b and notches 6 are provided in the inner side corner parts of the adjacent refractory bricks 4a. Water cooling tubes 7 are perpendicularly disposed in these notches. Plural pieces of the temp. sensors 8 are provided equidistantly from the slab 1 on the rear surface side of the coils 5 of the one side wall 4 and one piece of the temp. sensor 8 is provided on the other side wall 4. The temp. distribution on the surface of the slab 1 is measured by these sensors 8. The slab is thus heated by controlling the coils 5 until the vertical temp. distribution is uniformed.