In the production process of cold-drawn steel pipe, it is generally necessary to do some deformation treatment in order to make better use in the subsequent application process. Then how to do deformation treatment for cold-drawn steel pipe? When the punch drops and contacts with cold-drawn seamless steel pipe, the cold-drawn steel pipe bends at the beginning and at the rounded corner of the punch. Expansion and hardening occur in the site material. There are two kinds of deformation possibilities for cold-drawn seamless steel pipe when the punch continues to drop. One is that the blank at the bottom of the punch will elongate under two-way tension stress, the general product will increase and the thickness will decrease, i.e. the bulging deformation; the other is that the blank at the flange sector will straighten through the round corner of the concave die under tangential compressive stress and radial tension stress. The wall flow, general area reduction, thickness increase, that is, deep drawing deformation.
When the deformation resistance of cold-drawn steel pipe is equal to that of bulging deformation, the bulging at the bottom will proceed simultaneously with the drawing at the flange. If the drawing deformation resistance is less than the bulging deformation resistance, the blank at the bottom and the wall will not deform. The blank at the flange will transfer to the straight wall to form the cylinder wall, and the drawing deformation will proceed smoothly until the deformation is completed. If the deformation resistance in deep drawing is greater than that in bottom or joint, the bulging deformation will occur.
Because the expansion deformation level of cold-drawn steel tube is limited, the change of deformation means the beginning of splitting. Therefore, the normal drawing process is the deformation process of bending, bulging and deep drawing. Otherwise, it is a process of bending, bulging, drawing, bulging and splitting. Bending deformation always exists in the process of deep drawing. Bulging deformation exists either in the initial stage of deformation, or in the whole process of processing, or in the process of substitution with deep drawing deformation melon until the end of deformation or cracking of parts.
In the process of processing cold-drawn steel pipe, there are also some drawbacks, so it requires us to pay attention to the production process of cold-drawn steel pipe and try to reduce the occurrence of some defects.