At present, nondestructive testing includes ultrasonic testing, radiographic testing, penetrant testing, magnetic testing, etc.

① Radiographic inspection

radiographic flaw detection is a flaw detection method that uses the characteristics of penetrable materials and attenuation in materials to find defects. According to the different rays used for flaw detection, it can be divided into X-ray flaw detection γ Radiographic inspection and high-energy radiographic inspection. Due to the different methods of displaying defects, each radiographic inspection is divided into ionization method, fluorescent screen observation method, photography method and industrial television method. Radiographic inspection is mainly used to inspect cracks, incomplete penetration, pores, slag inclusions and other defects inside the weld.

② Ultrasonic flaw detection

when ultrasonic wave propagates in metal and other uniform media, it can be used to inspect internal defects because it will reflect on the interface of different media. Ultrasonic can inspect the defects of any weldment material and any part, and can more sensitively find the defect location, but it is difficult to determine the nature, shape and size of the defect. Therefore, ultrasonic flaw detection is often used in conjunction with radiographic inspection.

③ Magnetic inspection

magnetic inspection uses magnetic field to magnetize ferromagnetic metal parts to find defects. According to different methods of measuring magnetic flux leakage, it can be divided into magnetic particle method, magnetic induction method and magnetic recording method, of which magnetic particle method is the most widely used.

magnetic flaw detection can only find defects on the surface and near surface of magnetic metal, and can only make quantitative analysis on defects, and can only estimate the nature and depth of defects based on experience.

④ Penetrant inspection

penetrant inspection is to find and display defects by using the permeability and other physical properties of some liquids, including dye detection and fluorescent flaw detection. It can be used to check the defects on the surface of ferromagnetic and non ferromagnetic materials.