Ultrasonic Testing On PbSbSn Casting Alloy

The method of ultrasonic testing for casting of PbSbSn alloy is mainly studied in this paper. Its acoustics parameters are measured and the special focusing ultrasonic transducer is studied and made for testing. With optimizing testing parameters, ultrasonic testing to PbSbSn casting alloy is realized by direct contact method and water-immersion C-scan imaging method. The result of contrast test with radiography shows that ultrasonic imaging testing has higher sensitivity and reliability.Acoustics parameters of PbSbSn casting alloy was measured. Its longitudinal wave sound velocity is 2.346 km/s and its acoustic impedance is 24.39 × 106 kg.m-2/s. Its acoustic attenuation coefficient is 0.507±0.07 dB/mm which is measured with 2.5MHz longitudinal wave.The focusing transducer with spherical acoustic lens is studied and made. Its nominal element size is 20mm and its nominal frequency is 2.5MHz. Its focal distance in water is 25mm and its focal spot size is 2mm. The focal distance and focal size is batter than that of the transducer bought.The result of the ultrasonic testing to artificial defect on plate block shows that through compensating and controlling the coupling attenuation, three defects in PbSbSn alloy can be detected with direct contact method by improving impulse voltage to increase acoustic energy and decrease the effect of attenuation to testing depth and defect signs. Through optimizing ultrasonic testing parameters and using focusing transducer, the artificial blat-bottom hole with 1mm dimension can be detected with ultrasonic C-scan imaging system.It is known from the contrast test result between ultrasonic C-scan and radiography that the shape and the distribution of defects in PbSbSn alloy, thethickness of which is within 3mm, can be obtained with these two testing methods. Not only obtained images are similar which prove the testing method of ultrasonic C-scan imaging is reliable, but the depth of defect can be measured accurately with ultrasonic C-scan imaging method. When the thickness of PbSbSn alloy is beyond 3.5mm, the penetrating ability of X-ray detection apparatus is limited and only ultrasonic testing method can be used.