There are many factors affecting the drawing force in the drawing process of stainless steel pipes. According to the research, some of these factors are beneficial to the drawing process. On the contrary, other factors increase the difficulty of stretching. The drawing process and the performance of the drawn metal, heat treatment, deformation of each pass and drawing speed. The friction between the waste tube and the mold, lubrication, geometric dimensions and mold shape are closely related.
1. The material of waste tube
The chemical composition and organizational structure are different, and its mechanical properties are also different, which directly affects the pulling force. For example, the drawing force of No. 20 carbon steel and 36Mn2Si waste pipe must be much larger than that of No. 120 steel. The reason is mainly due to the different mechanical properties and insulation of the two materials.
The blank pipe produces work hardening during the drawing process, which increases the deformation resistance and reduces the plasticity. If the drawing is continued, the drawing force will continue to increase, which will promote the internal stress of the blank pipe to increase and easily produce cracks or crack defects. It is not sensitive to the barren pipe with uneven wall thickness. In order to eliminate the internal stress of the barren pipe after drawing, it should be annealed in time.
2. Drawing mold shape
It is mainly the shape of the outer mold for drawing (that is, the width of the working belt and the size of the drawing angle). The effect of the working belt width on the pulling force increases with the decrease of the deformation of the blank tube. Because when the amount of deformation is small, the waste pipe mainly enters the working zone under the compressive stress state of forced deformation, and the external friction force is generated between the waste pipe and the working belt to increase the pulling force. If the pulling angle is too large, the bending deformation of the waste pipe will increase, and the deformation stress will increase accordingly, which will increase the pulling force. Moreover, if the pull-out angle is too large, the lubrication condition will deteriorate, and the friction coefficient will increase, which will also increase the pull-out force. If the difference angle is too small, under the same deformation condition, when the ratio angle is large, the contact area will increase, which will increase the friction force and thus increase the pulling force. Therefore, the reasonable design of the pull-out angle is a very important factor, and it is generally more appropriate to adopt an angle of 12-13°.
The surface finish and hardness of the drawing mold have a very obvious influence on the drawing force. The mold should have sufficient hardness and good surface finish, which will reduce the friction between the contact surfaces and reduce the drawing force. Conversely, a poor mold does not have sufficient hardness and surface finish, which will inevitably lead to increased friction. Promote the increase of pulling force. Therefore, the preparation of the mold is a very important task, and the use of high-quality molds is one of the main conditions for obtaining high-quality steel pipes.
3. Preparations for waste management before pulling out
Such as pickling, washing, lubrication and other process quality is extremely important. It is directly related to the friction force during extension. A good preparation process greatly reduces the friction of shooting. Correspondingly, the pulling force is reduced. This creates favorable conditions for increasing the amount of stretching deformation.
The effect of the pulling speed on the pulling force is not obvious, which is proved by research and practical experience. When the drawing speed is increased, the drawing force in the drawing process increases slightly by about 4-8%. The differential speed continues to increase, and the drawing force does not change much, but increases slightly, and the increase is relatively gentle. This fully shows that it has nothing to do with the drawing speed, and it is entirely possible to increase the drawing speed and increase the output.
To sum up, there are many factors that affect the pulling force. Due to the different operation methods in the production process, the pulling force of the waste tube may be completely different. In order to improve the drawing conditions and reduce the drawing force, the selection of raw materials (that is, the waste pipe should have excellent materials and good mechanical properties, etc.). Reasonable preparatory work (such as pickling, rinsing, lubrication, heat treatment and other process quality), the distribution of deformation and the determination of drawing passes are all necessary conditions for the production of high-quality steel pipes.
1. The material of waste tube
The chemical composition and organizational structure are different, and its mechanical properties are also different, which directly affects the pulling force. For example, the drawing force of No. 20 carbon steel and 36Mn2Si waste pipe must be much larger than that of No. 120 steel. The reason is mainly due to the different mechanical properties and insulation of the two materials.
The blank pipe produces work hardening during the drawing process, which increases the deformation resistance and reduces the plasticity. If the drawing is continued, the drawing force will continue to increase, which will promote the internal stress of the blank pipe to increase and easily produce cracks or crack defects. It is not sensitive to the barren pipe with uneven wall thickness. In order to eliminate the internal stress of the barren pipe after drawing, it should be annealed in time.
2. Drawing mold shape
It is mainly the shape of the outer mold for drawing (that is, the width of the working belt and the size of the drawing angle). The effect of the working belt width on the pulling force increases with the decrease of the deformation of the blank tube. Because when the amount of deformation is small, the waste pipe mainly enters the working zone under the compressive stress state of forced deformation, and the external friction force is generated between the waste pipe and the working belt to increase the pulling force. If the pulling angle is too large, the bending deformation of the waste pipe will increase, and the deformation stress will increase accordingly, which will increase the pulling force. Moreover, if the pull-out angle is too large, the lubrication condition will deteriorate, and the friction coefficient will increase, which will also increase the pull-out force. If the difference angle is too small, under the same deformation condition, when the ratio angle is large, the contact area will increase, which will increase the friction force and thus increase the pulling force. Therefore, the reasonable design of the pull-out angle is a very important factor, and it is generally more appropriate to adopt an angle of 12-13°.
The surface finish and hardness of the drawing mold have a very obvious influence on the drawing force. The mold should have sufficient hardness and good surface finish, which will reduce the friction between the contact surfaces and reduce the drawing force. Conversely, a poor mold does not have sufficient hardness and surface finish, which will inevitably lead to increased friction. Promote the increase of pulling force. Therefore, the preparation of the mold is a very important task, and the use of high-quality molds is one of the main conditions for obtaining high-quality steel pipes.
3. Preparations for waste management before pulling out
Such as pickling, washing, lubrication and other process quality is extremely important. It is directly related to the friction force during extension. A good preparation process greatly reduces the friction of shooting. Correspondingly, the pulling force is reduced. This creates favorable conditions for increasing the amount of stretching deformation.
The effect of the pulling speed on the pulling force is not obvious, which is proved by research and practical experience. When the drawing speed is increased, the drawing force in the drawing process increases slightly by about 4-8%. The differential speed continues to increase, and the drawing force does not change much, but increases slightly, and the increase is relatively gentle. This fully shows that it has nothing to do with the drawing speed, and it is entirely possible to increase the drawing speed and increase the output.
To sum up, there are many factors that affect the pulling force. Due to the different operation methods in the production process, the pulling force of the waste tube may be completely different. In order to improve the drawing conditions and reduce the drawing force, the selection of raw materials (that is, the waste pipe should have excellent materials and good mechanical properties, etc.). Reasonable preparatory work (such as pickling, rinsing, lubrication, heat treatment and other process quality), the distribution of deformation and the determination of drawing passes are all necessary conditions for the production of high-quality steel pipes.
