INVESTIGATION OF METAL STRUCTURE BY NON-DESTRUCTIVE ULTRASONIC METHOD

The results of ultrasonic testing of metal before and after the operation of pipelines of thermal power plants are presented. Based on the metallographic analysis data, the frequency of ultrasonic waves was selected for research 10 and 15 MHz. It was found that the smallest effect of the surface roughness of the tested samples from the 12X1MF (Ra = 0.07…3.50 microns) was observed at a frequency of 15 MHz. It is shown that on the rough surface of samples Ra = 1.17…2.50 microns, the ratio of the amplitude of the 3rd bottom echo to the amplitude of the average noise level decreases to 17 dB at a frequency of 15 MHz with a metal operating time of 300 000 hours. The specified parameter is proposed to be used in metal structroscopy by ultrasonic method. It is shown that the shape of the pulse and its spectrum are subject to the greatest distortion at a frequency of ultrasonic waves equal to 15 MHz.