| 摘要 |
PURPOSE:To improve remarkably the pickling and descaling rate of a hot rolled steel sheet including a high-temp. coil by working the hot rolled steel sheet to strain the surface thereof to a specific value or above then subjecting the hot rolled steel sheet to pickling while applying ultrasonic waves thereto. CONSTITUTION:The hot rolled steel sheet 1 having the thick surface scale layer is strained to at least >=0.2% with rolling or a tension leveler 5. The strained and heated sheet 1 is put into pickling tank 2, 3 and is thereby pickled. The pickling in the soln. having a high acid concn. is particularly effective and the ultrasonic waves 4 are applied to the steel sheet in the acid soln. Cracks are generated in the surface layer by the strain thereof and are grown by the ultrasonic waves, by which the acid soln. is penetrated down to the deep part of the surface layer. The surface layer is forcibly stripped by the oscillation. Even the hot rolled steel sheet having the thick surface oxide layer such as the high-temp. coil is thus satisfactorily descaled.
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