Advantages and disadvantages of hot-rolled seamless steel pipe of large diameter

This improvement is mainly reflected in the direction along the rolling direction to a certain extent, the steel is no longer isotropic; pouring formed bubbles, cracks and loose, can be welded at a high temperature and pressure. Large diameter seamless steel pipe magnetic particle or penetrant testing can be an effective surface defects found in surface cracks, folding, heavy leather, hairline, pinholes. For ferromagnetic materials, magnetic particle testing method should be given priority, because of its high detection sensitivity; For non-ferromagnetic material, such as stainless steel seamless pipe, then using penetration testing method. When the ends of the reserve margin resection less, due to the structure detection means, both end detection may not be effective, and the terminal is most likely part of cracks or other defects. If the large-diameter seamless end there is a potential cracking tendency of the weld heat affected installation is also possible to make the potential of crack propagation. Therefore, it should be noted that after the detection of certain seamless steel tubes welded area, to detect defects in the expansion pipe ends. Online austenitic seamless carbon steel pipe, insulation is damaged or when the rain may have infiltrated the site, attention should conduct penetration testing to identify stress corrosion cracking or pitting corrosion and other defects.After hot rolling, the steel inside the non-metallic inclusions (mainly sulphide and oxide, and silicates) is pressed into the sheet, delamination (interlayer) phenomenon. Layered in the thickness direction of the steel tension performance deteriorated significantly, and there may be an interlayer tear weld shrinkage. Weld local strain-induced contraction of the yield point strain often reach several times larger than the load caused by the strain; residual stresses caused by uneven cooling. Residual stresses in the absence of external force from the internal equilibrium of stress, both hot-rolled steel section such various residual stress, the greater the cross-sectional size generally of steel, the residual stress is larger. Although the residual stress from equilibrium, but still has some influence on the performance of the steel members under loads. Terms such as deformation, stability, anti-fatigue effects may adversely. Hot-rolled steel products, poor control of the thickness and width of the edge in this respect. We are familiar with thermal expansion and contraction, since the beginning of the hot rolling out even the length, thickness are standard, and finally cooled or there will be some negative difference, this negative difference edge width wider, thicker the more obvious manifestations.