In the production process of cold-drawn seamless tubes, there are cold work hardening and hydrogen embrittlement, which are the main reasons for cracking of seamless tubes. This paper analyses two kinds of phenomena and puts forward some measures to prevent cracking of small diameter seamless steel pipe.


Analysis of Blasting Phenomenon Cold-drawn Seamless Pipe is formed by reducing the diameter of seamless pipe by drawing die. The processing route is generally annealing, pickling and wire drawing. In the process of drawing small diameter seamless steel tubes by drawing and cooling, cracks may begin to crack like bamboo ridges from the head to the tail. We call this phenomenon collective rupture.


The reasons for cracking are:
(1) Work hardening;
During cold drawing, the effect of work hardening on steel tube produces a lot of plastic deformation, which results in remarkable lattice deformation, thus increasing lattice energy and internal energy of metal, resulting in uneven internal stress and residual internal stress of metal. This increases the hardness and decreases the toughness of the metal. The higher the metal hardness is, the greater the residual internal stress is during cold drawing, and the more obvious the work hardening phenomenon is. When the residual stress reaches a certain value, the metal will tear along a certain grain boundary column and form cracks in the steel pipe.


(2) Hydrogen embrittlement.
Hydrogen embrittlement affects the reaction between phosphoric acid and iron, and releases hydrogen during acid scale removal. Hydrogen infiltrates into steel in the form of atoms or ions, forming a solid solution. The effect of hydrogen on mechanical properties of steel is usually hydrogen embrittlement.