Magnetic particle testing or penetration testing of seamless steel tubes can effectively find surface defects such as surface cracks, folds, heavy skins, hair lines, pinholes, etc. For ferromagnetic materials, the magnetic particle detection method should be preferred because of its high detection sensitivity; for non-ferromagnetic materials, such as stainless steel seamless steel pipes, the penetration detection method should be used.
When there is less allowance for removal at both ends of seamless steel pipes, due to the structure of the detection device, the ends of the two ends are sometimes not effectively tested, and the ends are the most likely parts of cracks or other defects. If there is a potential crack tendency at the end, the heat effect of welding during installation may also cause the potential crack to propagate. Therefore, attention should also be paid to the inspection of a certain area of the seamless steel pipe after butt welding, and the extension of the defects of the steel pipe end should be discovered in time.
For on-line use of austenitic seamless steel pipes, when the insulation layer is damaged or where rainwater may penetrate, attention should be paid to penetration testing to find defects such as stress corrosion cracks or pitting corrosion. However, magnetic particle or penetrant testing can only detect the outer surface of the steel pipe, and cannot do anything about the defects on the inner surface. The inspection of the inner surface, especially the inspection of cracks, must be carried out by ultrasonic inspection.
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