PURPOSE: To reduce pickling time by heating a steel sheet at the entrance side of a pickling tank, controlling the immersion time of the steel sheet by means of a sink roll in the pickling part, and discharging the acid liquid, scales and insoluble matters from the bottom of the tank.
CONSTITUTION: A steel sheet 1 is passed through a bridle roll 12, heated by a heating device 13, with the temp. controlled at 100-300°C by a thermometer 15, and pickled in a pickling tank 16 by way of a buckling preventing roll 22. The supporting angle of the steel sheet 1 is set at 30-60° against the level of the liquid into which the steel sheet 1 is immersed. The immersion time is controlled by the sink roll 1M. A hydrochloric acid solution with 4-8weight% is fed to the pickling tank 16 at the rate of 60-150kg per ton of steel sheets. The acid liquid is drained from the bottom of the tank 16 into a circulation tank 21. The concentration and the temp. of the acid liquid are adjusted in the circulation tank 21 with exhaust heat recovered by a heat exchanger 19 simultaneously. The steel sheet 1 is rinsed in a rinsing tank 20 and then sent to a succeeding process. Being heated and immersed in the tank 16, the steel sheet 1 is rendered to a nuclear boiling state, which causes minute cracks in the scales and enhances pickling effect.
KURIHARA MASANORI
ISHIGUCHI YUKIO
