1. Radiographic flaw detection method
Radiographic flaw detection is based on the fact that high-energy rays have a strong ability to penetrate the workpiece and produce a blackness difference after being absorbed in the material. It is more suitable for the flaw detection of medium and thin plate welds with relatively fixed workpiece positions. Single-wall single-shadow or double-wall single-shadow flaw detection methods are mostly used for pipe welds. However, for the material density test of straight and long seamless steel pipes, radiographic flaw detection is very unsuitable.
2. Ultrasonic flaw detection method
The ultrasonic flaw detection method of seamless steel pipes mostly adopts water immersion method or contact method. The flaw detection process is quite complicated and not as simple and convenient as eddy current flaw detection method. GB5777-86 "Ultrasonic flaw detection method for seamless steel pipes" clearly states: "The flaw detection method described in this standard is mainly to test the longitudinal or transverse defects of steel pipes, but cannot effectively detect delamination defects." Because it cannot detect defects in the annular direction or short and deep defects, which are precisely the defects that affect the density of steel pipes.
3. Magnetic particle flaw detection method
Magnetic particle flaw detection is only applicable to ferromagnetic materials and is suitable for detecting cracks and other defects on the surface or near the surface of the detection part. It cannot detect the deep-buried defects inside the workpiece, so it is not suitable for the density test of steel pipes.
4. Penetrant flaw detection method
The penetrant flaw detection method is suitable for the inspection of open defects on the surface of various materials, but cannot detect various defects inside the workpiece.
5. Eddy current flaw detection method
The eddy current flaw detection method is based on the principle of electromagnetic induction. It can detect surface defects or deeply buried defects, especially short and sudden shape defects. In addition, it has the characteristics of high speed, non-contact, and no coupling agent, so it is particularly suitable for pipe testing. This is why other non-destructive flaw detection methods cannot replace the density test of eddy current flaw detection.
