Ultrasonic flaw detection method for segregation defects of

Time : 2019-02-16 Author : Advanced Share :  
The structural parts used in some industrial equipment are made of aluminium alloy bars. The processing flow is sawing, warm extrusion forming, heat treatment (quenching, aging), roughing, finishing, anodic oxidation and appearance inspection. The structural parts bear high-pressure and high-speed movement in industrial equipment, so the quality of structural parts directly affects the overall quality level of industrial equipment. Small black spots were found on the surface of individual structural parts during the appearance inspection. Qualitative metallographic analysis showed that compound segregation was an impermissible quality defect in structural parts. In order to ensure the overall quality of industrial equipment, chemical segregation is effectively checked to remove structural parts with chemical segregation defects. The effective method is to detect and determine the segregation defects of compounds by ultrasonic testing.

The frequency of sound wave is controlled in the range of 0.5MHz to 25MHz by special instrument. At this time, the ultrasonic wave has linearity, beam property and strong directivity. When the ultrasonic wave is emitted to the tested material, the direction and intensity of the defect or other heterogeneous interface will be affected and reflected, refracted, scattered or absorbed during its propagation, so as to determine the size, physical properties, distribution mode and distribution position of the defect. The higher the ultrasonic frequency is, the better the resolution is and the smaller the size of defect particles can be found. According to the contact mode between probe and workpiece, it can be divided into direct contact method and water immersion method. Compared with the two methods, the water immersion method can eliminate the uncontrollable factors in the direct contact method, and has the advantages of improving the detection accuracy and speed. The ultrasonic flaw detection method is mainly suitable for detecting discontinuous defects. It is a relative detection method, not an absolute measurement method.

The ultrasonic flaw detection method can effectively detect the segregation defects of compounds in aluminium alloy structural parts, so that the product quality can meet the user's requirements. The application of ultrasonic flaw detection method provides a scientific basis for the implementation of ultrasonic detection of other defects that do not destroy the continuity of metals, and has the value of popularization.

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