The process of drawing stainless steel seamless steel pipe has many factors affecting the drawing force. According to results from many scientists and practical consumer operators, some of them are beneficial to the stopping of the drawing process. On the other hand, the other elements add the difficulty of stretching.
The process of stretching and drawing, the performance of stretching metal, heat treatment, and the stretching speed of each pass. The friction between the waste pipe and the mold, the smoothness, the geometric size and the shape of the mold are all intimate.
Stainless steel seamless
The material of stainless steel seamless pipe is different in chemical composition and structure. Its mechanical properties are also different, which directly affects the strength of drawing. For example, the drawing force of No. 20 carbon steel and 36Mn2Si waste pipe must be much larger than that of No. 120 steel, mainly because of the different mechanical properties of the two materials.
The stainless steel seamless pipe produces work hardening during the drawing process, so that the deformation resistance increases and the plasticity decreases. When the difference continues to stretch, the drawing force continues to increase, which causes the internal stress of the waste pipe to increase, which is prone to cracks or crack defects, and the wall thickness is uneven.
The ridiculous pipe is not sensitive, in order to eliminate the internal stress of the barren pipe after stretching, it should be annealed in time. Stretching the shape of the mold, mainly to stretch the shape of the outer mold (ie, the width of the working belt and the size of the extension angle).
The effect of the width of the working belt on the drawing force is increased as the amount of deformation of the waste pipe decreases. Due to the small deformation amount, the waste pipe is mainly subjected to the compressive stress state of forced deformation and enters the working belt, and the external friction force between the waste pipe and the work belt increases the drawing force.
If the angle of the drawing is too large, the bending deformation of the waste pipe will increase and the deformation stress will increase accordingly, so that the pulling force will increase. Moreover, the stretching angle is too large to deteriorate the smoothing condition, and the increase of the friction coefficient also increases the drawing force.
If the difference angle is too small, the contact area increases when the angle is large, and the frictional force increases, so that the pull-out force increases. Therefore, the reasonable design of the extension angle is very only required, and the common angle is 12 to 13°.
Brightness and hardness
The effect of the brightness and hardness of the external drawing on the drawing force is ten. The mold should have sufficient hardness and good external brightness, which will reduce the friction between the contact surfaces and reduce the drawing force. small. Conversely, the poor mold does not have sufficient hardness and appearance brightness, which inevitably leads to an increase in friction. Promote the increase in extraction force.
Therefore, the preparation of the mold is a very important task, and the use of high-quality mold is one of the main conditions for obtaining high-quality steel pipes. The preparation of the former waste pipe (ie the pipe branch); the quality of the process such as pickling, washing and smoothing is extremely important. It is directly related to the friction during stretching.
A good preparation process greatly reduces the pulling friction. Correspondingly, the pulling force is reduced. This has created favorable conditions for the advancement of the deformation. The effect of the stretching speed on the drawing force is not obvious. It is proved by the research and theoretical experience of the former Soviet scientists and technicians; the drawing speed of the drawing and drawing process is slightly increased by about 4 to 8%, and the speed is poor.
Continued progress, the change in the force of extraction is not large, slightly increased, and the increase is relatively flat. This is sufficient to clarify that there is no relationship with the speed of stretching. It is possible to improve the speed of stretching and increase the output. In summary, the factors affecting the pull-up force are more numerous.
Due to the different operation modes in the consumption process, the drawing force of the waste pipe is likely to be completely different. In order to improve the drawing conditions and reduce the drawing force, the choice of the original data (ie, the waste pipe should have excellent materials and good mechanical properties, etc.) Reasonable preparation work (such as acid west, flushing, smoothing, heat treatment and other process quality), the distribution of deformation and the extension of the road are indeed necessary conditions for the consumption of high-quality steel pipe.