| 摘要 |
PROBLEM TO BE SOLVED: To surely apply ultrasonic waves to a steel sheet surface and to uniformly and efficiently execute pickling by arranging an, ultrasonic vibrator transducer array perpendicularly to the transporting direction of the steel sheet in an ultrasonic pickling tank and bringing the vibration surfaces of the ultrasonic vibrator transducers into proximity to the steel sheet at a distance below a boundary layer thickness. SOLUTION: The hot rolled steel sheet 3 is immersed in the pickling tank 1 or rinsing tank and is transported therein, by which the steel sheet is pickled and descaled. The ultrasonic vibrator transducers 4 having the plane vibration surfaces are arranged in this tank 1 at the array of the length below the length of the tank 1 and the width below the width of the hot rolled steel sheet 3 and below the width of the tank 1 perpendicularly to the transporting direction of the hot rolled steel sheet 3. Further, the vibration surfaces of the transducers 4 are brought into proximity to the hot rolled steel sheet 3 at the distance below the thickness of the boundary layer formed by the transportation of the hot rolled steel sheet. As a result, the ultrasonic waves pass an acid liquid and are applied to the hot rolled steel sheet 3 through the liquid without being drifted or diffused by the accompanying flow of the boundary layer, by which the infiltration of the acid liquid between the base metal and the scale is accelerated and mechanical force is applied to the hot rolled steel sheet 3 to accelerate the scale removal.
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