In the production process of ASTM A179 cold drawn seamless pipe, chill and hard brittleness occurred, which is the main reason for cold drawn seamless pipe cracking.
The ASTM A179 cold-drawn seamless pipe bursting phenomenon is analyzed. It is a small-diameter seamless steel pipe. It is cold-formed and cold-formed by drawing die. The process route is generally annealing, pickling and drawing. In the process of drawing, the cold-drawn small-diameter seamless steel pipe sometimes cracks like a bamboo piece from beginning to end, which we call a crack phenomenon.


The reason for cracking is:


Under the action of work hardening, the steel pipe generates a large amount of plastic deformation during cold drawing, which causes obvious lattice deformation, increases lattice energy, increases the internal energy of the metal, leads to uneven internal stress of the metal, and uneven residual stress. . pressure. This will increase the hardness of the metal and reduce the toughness. The higher the hardness of the metal, the greater the residual internal stress during cold drawing and the more obvious the work hardening phenomenon. When the residual stress reaches a certain value, the metal will tear along a certain particle interface to form a steel pipe crack.


The effect of hydrogen embrittlement, in the process of acid descaling, sulfuric acid and iron react to form hydrogen. Hydrogen penetrates into the steel in the form of atoms or ions to form a solid solution. The effect of hydrogen on the mechanical properties of steel is a typical hydrogen embrittlement phenomenon.