| The whole structure, parameters and working mechanism of the ultrasonic on-line testing equipment was completely analyzed and recognized. The key part of the equipment is the probe system that contains transverse and longitudinal probe brackets, steel plane testing pot, probe adjusting pot and serving pot. The whole equipment can realize the automatic testing and controlling by 5 computers and a Programmable Logic Controller.Some defects such as delamination, impurity and crack found during the ultrasonic automatic detection were also analyzed through metallographic analysis with high and low magnification, it have been verified that the size detected by both methods for same defect also identical.The probe system was calibrated and equalized by preparing three series of standard compared samples used for probe testing. Through the equalizing of (DAC) curves, (TCG) curves can be formed which are suitable to the practical use in factories. After gain calibrating and spot sensitivity adjusting, the fluctuation amount of the dB in the TCG curve got from the equalization of different type of steel planes was lower than 1dB. The adverse effect of changes in thickness as the steel planes on the testing result was cleared up.The dynamic on-line testing results of the compare samples showed that the calibrated and equalized probe system can accurately detect the all 15 defects in the dynamic compare samples. The detecting ability of the equipment can reach the national standards and international related standards.Using the ultrasonic automatic testing system, the detecting time was shortened from 98s/sheet to 18 min/sheet, the error rate was reduced from 11.2% to 0.5%.
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