Castings are widely used in machinery, construction, shipbuilding, aerospace, automobiles, locomotives and other fields due to their many advantages. In some important applications, non-destructive testing of the inherent quality of castings is essential, and can be used for quality testing of castings. Non-destructive testing techniques include penetration testing, magnetic particle testing, eddy current testing, radiographic testing and ultrasonic testing. Penetration testing is used to check various opening defects on the surface of castings, such as surface cracks, surface pinholes and other defects that are difficult to find with the naked eye. Eddy current testing is suitable for checking defects that are generally not more than 6 to 7 mm deep below the surface. The main disadvantage of eddy current inspection is that it cannot visually display the size and shape of the defect. Generally, it can only determine the surface position and depth of the defect. In addition, it is not as sensitive as penetrant inspection for detecting small opening defects on the surface of the workpiece. Magnetic particle inspection is suitable for detecting surface defects of ferromagnetic material castings and defects several millimeters deep below the surface. For internal defects, the commonly used non-destructive testing methods are radiographic testing and ultrasonic testing. Among them, radiographic testing can obtain intuitive images that reflect the types, shapes, sizes and distribution of internal defects, but for large-thickness large castings, ultrasonic testing is very effective, and the location, equivalent size and distribution of internal defects can be measured more accurately Happening.
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