What will affect the tensile strength of stainless steel seamless steel pipe?

What will affect the tensile strength of stainless steel seamless steel pipe?

There are many factors that affect the drawing force during the drawing process of stainless steel seamless steel pipes. According to research, some of these factors favor the drawing process. Conversely, other factors can make stretching more difficult. Drawing process and properties of drawn metal, heat treatment, deformation per pass and drawing speed. The friction, lubrication, geometric dimensions and mold shape between the waste pipe and the mold are closely related.

1. Waste pipe material

Different chemical compositions and organizational structures have different mechanical properties, which directly affect the tensile force. For example, the pulling force of No. 20 carbon steel and 36Mn2Si scrap pipe must be much greater than that of No. 120 steel. The reason is mainly due to the different mechanical properties and insulation properties of the two materials.

The tube blank produces work hardening during the drawing process, which increases the deformation resistance and reduces the plasticity. If you continue to pull, the pulling force will continue to increase, which will increase the internal stress of the blank tube and easily cause cracks or crack defects. Insensitive to rough pipes with uneven wall thickness. In order to eliminate the internal stress of the drawn waste pipe, it should be annealed in time.

2. Draw the mold shape

Mainly the shape of the outer mold of drawing (that is, the width of the working belt and the size of the drawing angle). The influence of working belt width on tensile force increases with the decrease of tube blank deformation. Because when the deformation is small, the waste pipe enters the work area mainly under the compressive stress state of forced deformation, and external friction is generated between the waste pipe and the work belt, increasing the tensile force. If the pulling angle is too large, the bending deformation of the waste pipe will increase, the deformation stress will increase accordingly, and the pulling force will increase. Moreover, if the drawing angle is too large, the lubrication conditions will deteriorate, the friction coefficient will increase, and the drawing force will also increase. If the difference angle is too small, under the same deformation conditions, when the ratio angle is larger, the contact area increases, the friction force increases, and thus the pulling force increases. Therefore, the reasonable design of the extraction angle is a very important factor. Generally, an angle of 12-13° is more suitable.

The surface finish and hardness of the drawing mold have a very obvious impact on the drawing force. The mold should have sufficient hardness and good surface finish, which will reduce friction between contact surfaces and reduce pulling force. On the contrary, inferior molds do not have sufficient hardness and surface finish, which will inevitably lead to increased friction. Promote the increase of pulling force. Therefore, the preparation of molds is a very important task, and using high-quality molds is one of the main conditions for obtaining high-quality steel pipes.

3. Preparations for waste disposal before evacuation

The quality of processes such as pickling, water washing, and lubrication is extremely important. It is directly related to the friction during stretching. A good preparation process can greatly reduce the friction of shooting. Correspondingly, the pulling force decreases. This creates favorable conditions for increasing the amount of tensile deformation.

The effect of pulling speed on pulling force is not obvious, which has been proven by research and practical experience. When the drawing speed increases, the pulling force during the drawing process increases slightly, about 4-8%. The differential speed continues to increase, and the pulling 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 can completely increase the drawing speed and increase the output.

To sum up, there are many factors that affect pulling force. Due to different operating methods during the production process, the pulling force of the waste pipe 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 material and good mechanical properties, etc.). Reasonable preparation work (such as pickling, rinsing, lubrication, heat treatment and other process quality), distribution of deformation and determination of drawing passes are all necessary conditions for the production of high-quality steel pipes.