Cold drawn pipe processing work hardening happened to some extent, in the cold drawn process of the metal in the plastic deformation, the crystal inside will have more than one slip system start, by cold drawn processing metal internal dislocation density increases, the dislocation mobility is reduced, is difficult to produce dislocation and difficult to mobile dislocation, and hardness, strength, improve the metal materials. This is the metal principle of cold drawn.
The key factors of cold drawn tube
Mainly in the production process of cold drawn tube based on the effect of hot rolled tube as the main material of processing of drawn together, in its operation of hot rolled tube material, specification, quality selection of appropriate or not directly affects the drawn and the finished product quality. The following points should be noted when selecting materials:
1． When selecting materials, the cold-drawn tube usually selects materials with low hardness and good plasticity under the condition of strength guarantee.
2． The specification of cold-drawn steel pipe should be selected according to the specifications of its finished products, so as to effectively ensure its elongation rate of 20 to 40 percent. The elongation rate is too small, and the strength of the finished product surface cannot be guaranteed.
3． Material surface can not have pit, crack, crack, fold, scar, ellipse and other serious defects
4． Had better choose 0.5 ~ 2 a placement after hot rolling steel tube, time is too short, steel pipe surface rust shallow, time is too long, steel pipe surface rust too deep, these can lead to inadequate steel tube surface pretreatment, thus affecting the surface quality of the product.
Mechanical principle of cold drawn tube
In the process of making cold-drawn tube, the main effect of force is the plastic deformation of the tube to a certain extent through certain shape, size and mould. At present, the production method of drawn can be roughly divided into three kinds: reducing tube drawn, subtract the outer wall tube drawn and reduction of wall tube drawn, cold drawn, the steel tube in the drawn force, friction force and the normal pressure, under the action of the corresponding deformation occurs, mostly through reducing, reducing wall and sizing three stages, and the corresponding stress is generated in the deformation zone of axial tensile stress, radial and circumferential stress, metal tube drawn process is always pull and two to the compressive stress state, this is the basic mechanical characteristics of cold drawn pipe deformation process.