Stratification of Seamless Steel Tube

Seamless Steel delamination crack direction: the roots-oriented cracks, the crack tip passivation. After passivation of stainless steel rod ends crack than the previous smaller ends of the hair, the crack tip opening. Ax the crack tip is smaller than the previous crack at the crack tip to produce a passivated smaller than the first section. Times delamination crack. Second delamination crack and the crack between the first layered material stainless steel rod to pull off, the main crack, breaking with the main crack propagation direction 450. Feng crack propagation along a straight line path will not be extended, between the delamination crack formation oblique shear failure surface. Master Ding main vertical crack crack crack layering direction, its expansion in the material need to consume more energy to make it more difficult to crack. Thus, by the weak pipeline delamination crack at the crack interface generated for the pipeline surface defects or cracks to penetrate the wall of the table and the expansion of thick-walled seamless evolution hinder effect on the formation of resistance I Bu Crack and leaky pipes have a beneficial effect. Regardless of how the orientation of the sample, were produced before the delamination crack crack thick-walled seamless abundance. In the fracture process, the stress state influence on the delamination crack crack tip is very large, and thus have an enormous impact on the fracture. In normal use, there is no feed pipe tree delamination crack, thick-walled seamless steel pipe delamination cracks in the fracture process only towel, and delamination crack fracture has no effect on the normal use of the pipeline. In addition, generated when the delamination crack fracture need to consume more energy, while the delamination crack crack penetrates the body to make it effective thickness decreases, the vertical stratification cracks and crack propagation direction of the surface crack body, all these factors make more difficult to crack, and the material toughness is improved. The main purpose of seamless steel is high-strength structural steel. Drawbacks delamination mechanism, the general view that the non-metallic inclusions in the tube will destroy the continuity and compactness of the pipe, even serious inclusions generated in the carbon steel pipe inner stratification. Another thought to be hydrogen-induced cracking, that due to the accumulation of hydrogen in steel metal internal gas pressure caused by excessive formation of white spots in the round tube, crack extension occurs during the rolling process, and ultimately the formation of layered defects. In addition, the stress exceeds the strength of two rolls of plastic rotary piercing uneven deformation can also cause delamination. In the case of smelting strict control, the control measures is improve the cleanliness of molten steel, reducing harmful inclusions; increase the proportion of the slab crystal axis, to reduce the center segregation and center porosity; using reasonable cooling system to avoid appearance of blooms the crack; billet or rolling slab to be taken offline slow cooling process, reducing internal stress, thus ensuring the microstructure and mechanical properties of the finished tube and pipe meet the technical standards. By measuring thermoplastic curve, choose the best heating temperature. Note also that there is enough heating tube holding time, in order to reduce the plastic deformation resistance and improved toughness. Roll speed is a critical parameter of the piercing process, the roll speed changes from low to high in the process, there is a critical start delamination roll speed. Lower roll speed, easy to form a tube bore; higher roll speed, and capillary tube formation of layered defects easily. In order to eliminate delamination defects and capillary tube, roll speed should be reduced to the start of the critical delamination roll speed less.