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  • Cangzhou Steel Pipe Group (CSPG) Co., Ltd.
  • ADD:No.92 Jiefang East Rd., Cangzhou City, Hebei Province, China
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  • Principle of cold drawn tube
    Oct 29, 2018

    1. Principles of metallography

    It is the work hardening of the cold drawn steel pipe. The metal is plastically deformed during cold drawing, and multiple slip systems are started inside the crystal. The dislocation motion intercepts each other, many dislocations are pinned, causing dislocation accumulation, and the dislocation source stops. The above series of processes leads to a decrease in the mobility of dislocations and a significant increase in dislocation density in the crystal. When the plastic deformation occurs further, the stress increases enough to cause the dislocation of the pinning to start moving, the screw bit is misaligned and slipped, and the blade dislocation cannot be slipped, so that the dislocation is intercepted, and the degree of immobility is increased.

    Therefore, by increasing the internal dislocation density of the metal by cold drawing, the dislocation movability is lowered, and it is difficult to generate dislocations and it is difficult to move dislocations, so that the hardness and strength of the metal material are improved. This is the metallurgical principle of cold drawing.

    2, the mechanics principle

    When cold drawing, the steel pipe is plastically deformed by a mold of a certain shape and size under the action of force. At present, the extraction method in production can be roughly divided into three types: reduced diameter extubation, reduced outer wall extubation and reduced inner wall extubation. When cold drawn, the steel tube occurs under the action of drawing force, positive pressure and friction. Corresponding deformations are mostly subjected to three stages of diameter reduction, wall reduction and sizing, and corresponding stresses are generated inside the deformation zone, wherein the axial direction is tensile stress, the radial direction and the circumferential direction are compressive stresses, and the metal is always in the process of extubation. Pulling and two-direction compressive stress state, which is the basic mechanical feature of the cold drawn tube deformation process.