During the production of ASTM A179 cold-drawn seamless steel tube, there are cold hardening and hydrogen embrittlement phenomena, which are the main causes of cracking of cold-drawn seamless steel tube.


The cracking phenomenon of AM9 cold-drawn seamless pipe is analyzed. The diameter of the seamless pipe is smaller by cold forming with drawing die. The process route is generally annealing, pickling and drawing. In the process of drawing cold-drawn small diameter seamless steel tubes, sometimes cracks occur from beginning to end like cracks in bamboo, which we call cracks.


The reasons for cracking are:
Under the influence of work hardening, a large number of plastic deformation occurs during cold drawing of steel tubes, which results in obvious lattice deformation, which increases lattice energy and internal energy of metals, resulting in uneven internal stress and residual stress of metals. 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, forming steel pipe cracking.


In the descaling process of acid, sulphuric acid and iron, hydrogen embrittlement will precipitate hydrogen. Hydrogen penetrates into steel in the form of atoms or ions to form solid solutions. The effect of hydrogen on mechanical properties of steel is a typical feature of hydrogen embrittlement.