Seamless precision steel pipe products have problems of uneven eccentric thickness, but what are the reasons? Many people don’t understand, today we will talk about how to produce eccentricity of seamless steel pipes such as cold drawn steel pipes, cold rolled steel pipes and hot rolled steel pipes. Rate, why the concentricity of seamless steel pipes is not so ideal? Eccentric steel pipes are the most easily produced in the production of hot rolled steel pipes, and most of the connecting rods are produced during the hot perforation process.
Through the anatomical analysis of the steel pipe after the automatic pipe rolling machine, it is considered that the vertical and horizontal wall thickness distribution of the perforated pipe after the automatic pipe rolling machine is rolled unevenly, and the characteristics of the perforated pipe are basically maintained. The wall thickness of the perforated pipe is unevenly distributed, that is, the pipe wall still has a spiral wall thickness non-uniformity after rolling, and the lateral wall thickness unevenness increases obviously.
First, the reasons for the uneven wall thickness of the automatic tube rolling machine are:
1. The shape and severity of uneven wall thickness of porous capillary directly affect the shape and severity of uneven wall thickness of steel pipe after rolling.2. When the steel pipe is rolled on the automatic pipe rolling machine, the wall thickness is uneven due to the bending of the ram, so that the position of the head is deviated from the center of the hole type, so that the position of the maximum wall thickness and the minimum wall thickness on the pipe section is deviated. The wall thickness and the tube head are almost fixed, and the wall thickness unevenness from the tail to the tube head is gradually increased, thereby reducing the residual bending of the ram. The axial force of the ram during low roll rolling has a significant effect on reducing wall thickness unevenness.
3. The larger the wall reduction, the more serious the wall thickness of the waste pipe is. When the wall reduction is small, the automatic pipe rolling machine has the effect of reducing the uneven wall thickness of the perforated pipe. The hole shape is not adjusted correctly. When the roll gap is not parallel, the wall thickness of the waste pipe will be intensified.Second, the seamless steel pipe plant carried out a Fourier transform on the measured wall thickness data of the Φ400mm automatic rolling pipe unit, perforation, secondary perforation (extension), automatic rolling pipe and equalizing four rolling processes, and obtained the wall thickness. The quantitative analysis of the mean and the reasons for its formation, and based on this, proposed ways to improve the wall thickness of the steel pipe:
1. After the secondary perforation (extension), the distribution of the uneven thickness of the spiral wall on the waste pipe is retained to the finished pipe, so improving the secondary perforation (extension) is the key link to improve the wall thickness accuracy of the finished pipe. The main measure is Improve the tool design to increase the concentricity of the ram and the head with the rolling line during the rotation.
2. Improving the uneven thickness of the capillary tube after perforation is an important part. The main measures are to improve the heating uniformity of the tube blank, improve the precision of the centering hole, lengthen the length of the entire belt and the length of the reverse cone, and improve the ejector and the head. Concentricity with the rolling line during the rotation.
3. Although the symmetrical wall thickness unevenness will occur during the rolling process, it does not have a certain effect on reducing the spiral wall thickness. Therefore, two tubes should be rolled during the rolling process, and the waste pipe should be turned over 90° between the passes.