Radiography, using X-rays or radioactive isotopes produced by X-ray tubes γ A non-destructive testing method for radiographic penetration of workpieces using film as a recording device for information. This method is the most basic and widely used radiographic testing method The principle of radiography is essentially the use of electromagnetic waves or radiation (X-rays and γ The energy of radiation. During the process of penetrating an object, rays interact with matter, weakening their intensity due to absorption and scattering. The degree of intensity attenuation depends on the attenuation coefficient of the material and the thickness of the ray penetrating through the material. If there are defects in the local area of the object (workpiece) being penetrated, and the attenuation coefficient of the material that constitutes the defect is different from that of the test piece (for example, in the weld seam, the attenuation coefficient of the air inside the porosity defect is much lower than that of the steel), the intensity of the transmitted rays in the local area will differ from the surrounding area. Place the film in a suitable position to make it sensitive to light through the action of radiation, and process it in a dark room to obtain the negative film After the ray penetrates the workpiece, due to the difference in transmission ray intensity between the defective and intact parts, there will be differences in blackness in the corresponding parts on the negative film. Radiographers can identify the location and nature of defects based on the differences in blackness of negative films by observing them Radiography is a method that can be applied to butt joints of various fusion welding methods in steel structures, as well as to inspect cast steel components. In special cases, it can also be used to detect fillet welds or other special structural workpieces. Radiography method for detecting wall defects in metal steel pipes The advantages of radiographic method (1) intuitive defect display: Radiography uses negative film as the recording medium, and by observing the negative film, the nature, quantity, size, and position of defects can be accurately determined. (2) It is easy to detect defects that form local thickness differences: there is a high detection rate for defects such as pores and slag inclusions. (3) The length and width dimensions that can be detected by radiography are on the order of millimeters and sub millimeters, or even fewer, respectively, and there is almost no lower limit for the detection thickness. (4) It is applicable to almost all materials and can achieve good results when used on metal materials such as steel, titanium, copper, and aluminum. This method does not have strict requirements for the shape and surface roughness of the specimen, and the material grain size does not affect it The limitation of radiographic method (1) is that the detection rate of crack like defects is affected by the transmission angle and cannot detect thin layer defects in the vertical irradiation direction, such as delamination of steel plates. (2) The upper limit of detection thickness is limited by the ability of ray penetration. (3) The radiographic method has a higher cost and slower detection speed. (4) Radiation can cause harm to the human body and protective measures need to be taken