Seamless tube is widely used in our days, can be said to be very common in daily life, but I do not know whether you have investigated, sometimes the appearance of seamless tube presents some horizontal lines, do not have any problems, so what is the reason?

If the deformation of thick-walled seamless pipe is small in the process of empty drawing, the additional stress of external pressure and internal pull will occur in the outer and outer layers. At this time, because of poor deformation permeability, the extension trend of the outer and outer layers is larger than that of the inner layer, so the compressive stress occurs in the outer and outer layers, and the stress occurs in the outer and inner layers.If the stress attached to the surface of the inner surface is large, the fundamental stress and additional stress added together during drawing will exceed the extent permitted by the strength of the thick wall seamless tube, resulting in transverse cracking of the inner surface.

Under the corresponding mechanical conditions, the various factors that reduce the plasticity of seamless tube will increase the time of internal transverse crack.Therefore, the annealing quality and elimination of hydrogen embrittlement are very important in the production of thick wall seamless tubes.

In addition to axial additional stress, there is tangential additional stress in the process of empty drawing.The longitudinal crack is caused by the additional tangential tensile stress during empty drawing.