| 摘要 |
PURPOSE:To stably maintain an atmosphere in an annealing furnace and to suppress decarburization so as to permit easy descaling by keeping the pressure in the furnace set at a positive pressure, the total oxygen concn. in a specific range and the temp. of a heating stage at an adequate temp. respectively at all times. CONSTITUTION:Steel products 18 are passed through a heating stage and a furnace cooling stage and are thereby annealed while the steel products 18 carried into the furnace body 1 consisting of a heating zone A consisting of a heating-up part A1 and a holding part A2 provided with burners 7 for heating and a furnace cooling zone B from a charging port 2 provided with a shutter 41 are transferred by a conveyor 5; thereafter the steel products are ejected from a take-out port 3 provided with a shutter 42. The pressure in the furnace in the furnace and cooling stage of the direct firing type combustion furnace for annealing constituted in the above-mentioned manner is kept always at the positive pressure by pressure control burners 8 to prevent the suction of the air. An air supply source 12 is controlled by an oxygen concn. sensor 9, air-fuel ratio control part 17 and the 2nd control part 152 to maintain the total oxygen concn. in the furnace at 0.5-2.5% at all times to grow the generation of scale. A fuel supply source 11 is further controlled by a temp. sensor 10, a temp. control part 16 and the 1st control part 151 by which the in-furnace temp. of the heating stage is set at <=750 deg.C to control the growth of scale.
|
