Radiography:radiographic testing RT for short, its basic principle is that when the ray beam with uniform intensity penetrates the object to be tested, if there is defect or structure difference in the local area of the object, it will change the attenuation of the object to the ray, so that the intensity of the transmitted ray in different parts is different. In this way, using a certain detector to detect the intensity of the transmitted ray can determine the internal defects and material distribution of the object. As one of the five conventional nondestructive testing methods, radiographic testing is widely used in industry. It is not only used in metal inspection, but also in non-metal inspection. The defects that may occur inside the metal, such as pores, pinholes, inclusions, looseness, cracks, segregation, lack of penetration and fusion, can be detected by the method of ray inspection.