Cold-drawn tube processing has undergone work hardening to a certain extent. During the cold drawing process, its metal undergoes plastic deformation, and there are multiple slip systems inside the crystal. The internal dislocation density increases through 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.
Key factors for drawing cold drawn tubes
In the process of making the cold drawn pipe, the hot rolled pipe is mainly used as the main processing material. The selection of the material, specification and quality of the hot rolled pipe directly affects the operation. Drawing progress and quality of finished products. Pay attention to the following points when selecting materials:
1. When the cold drawn pipe is selected, the material with low hardness and good plasticity is generally selected under the condition of strength guarantee.
2. The specifications of the cold drawn pipe should be selected according to the specifications of the finished product, so that the elongation can be effectively guaranteed to be 20% to 40%; the elongation is too small, and the strength of the finished surface cannot be Guaranteed, too large, making drawing difficult.
3. The surface of the material must not have serious defects such as pits, cracks, cracks, folds, crusting, and ellipse.
4. It is best to choose a steel pipe with 0.5~2a after hot rolling. The time is too short, the surface of the steel pipe is rusted and shallow, the time is too long, and the surface of the steel pipe is too rusted. These will lead to insufficient pretreatment of the steel pipe surface, thus affecting the surface quality of the finished product.
Mechanical principle of cold drawn tube
In the process of making the cold drawn tube, the plastic deformation is mainly caused by a certain shape, size and mold. 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. The corresponding deformations are mostly through 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 stress, 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.