METHOD AND APPARATUS FOR ULTRASONICALLY DETECTING FLAW ON SURFACE OF CIRCULAR CYLINDER, AND METHOD OF GRINDING ROLL UTILIZING THE SAME

摘要

The invention is for ultrasonic testing using surface waves, and its object is to prevent false detection of primary cracks, to lower the level of structural noises from grain boundaries, and to improve the detectability in the ultrasonic testing. Concretely, in surface wave testing of hot rolling rolls, used is a surface wave probe 10 capable of transmitting and receiving a surface wave and provided with a piezoelectric element 10A, a resin wedge 10C disposed on the front surface of the piezoelectric element 10A and a damping block 10B disposed on the back surface thereof, and the surface wave probe 10 is driven to produce a short pulse having a pulse length of being at most 2.5 times the wavelength of the surface wave to be produced. In this, a coupling liquid medium is supplied to the probe 10 in accordance with the peripheral speed of the roll to be tested. Depending on the height of the reflected waves measured, the grinding allowance of the roll is determined, and the roll is ground according to the thus-determined grinding allowance. The roll may be tested while being partly ground, and the optimum grinding allowance of the roll may be determined. IMAGE