Friday, June 28, 2013

Advantages of hot-rolled large diameter seamless steel pipe

Large diameter seamless hot-rolled advantages: destroy the ingot casting organizations, grain refinement of steel and eliminate defects in the microstructure, so that the dense tissue steel, mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer certain extent isotropic; pouring bubbles formed cracks and porosity, but also in under the action of high temperature and pressure welding.

Large diameter seamless steel pipe magnetic particle testing or penetrant testing can effectively find surface cracks, folds, double skin, hairline, pinholes and other surface defects. For ferromagnetic materials, magnetic particle inspection method should be preferred, because of its high detection sensitivity; For non-ferromagnetic material, such as stainless steel seamless pipe, then a penetration assay.

Reserved resection margin when both ends is small, causes the detection apparatus, both ends of the head may not be effectively detected, and ends there is most likely the site of cracks or other defects. If large-diameter seamless steel pipe ends there is a potential tendency to crack, the installation of the weld heat affected also possible to make the potential crack. Therefore, it should be noted that certain areas of the welded steel tube detection, to detect defects in steel tip extensions. Use the online austenitic seamless insulation is damaged or when rain may have infiltrated the site, should pay attention to the infiltration testing to find stress corrosion cracking or pitting corrosion and other defects.

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