METHOD FOR CONTROLLING TEMPERATURE OF HEAT TREATING INSTALLATION

PURPOSE:To maintain always constant the temp. of a steel strip in the outlet of the 2nd heating furnace in the stage of heat-treating the steel strip in the 1st heating furnace having fast responsiveness and the 2nd heating furnace having slow responsiveness by controlling the quantity of the heat input to both furnaces by the temp. of the steel strip in the outlet of both furnaces. CONSTITUTION:The steel strip 38 is heated to about 1,000 deg.C to burn the org. materials sticking thereto in the direct firing type 1st heating furnace 40 having fast responsiveness. Said strip is heated to about 1,200 deg.C in a reducing atmosphere and is thus annealed in the 2nd heating furnace 42 using radiant tubes 50 and having slow responsiveness. The temp. of the strip 38 in the outlet of the furnace 42 is measured by a thermometer 60 and if said temp. is lower than the target temp., the quantity of the heat input is increased by controlling the control valve 64 for the fuel supply pipe 46 of the furnace 40 with the signal thereof. The temp. of the strip in the outlet of the furnace 40 is measured by a thermometer 52 and the quantity of the heat input to the inside of the radiant tubes in the 2nd heating furnace is made higher as the temp. is higher so that the heating temp. of the steel strip by the 1st heating furnace having fast responsiveness and the heating furnace having slow responsiveness is maintained always constant.