Reasons for uneven wall thickness of ms seamless pipes

Reasons for uneven wall thickness of ms seamless pipes:

The finished product of ms seamless pipe will have the problem of uneven thickness and eccentricity, but how does this happen? Many people don't understand. Today we will talk about how the eccentricity of ms seamless pipes such as cold-drawn steel pipes, cold-rolled steel pipes, and hot-rolled steel pipes occurs. Why is the concentricity of ms seamless pipe less than ideal?

Steel pipe eccentricity is most likely to occur in the production process of hot-rolled steel pipes, and most of the links occur during hot piercing:
 
Based on the anatomical analysis of the steel pipes rolled by the automatic pipe rolling machine, we believe that after the perforated capillary tube is rolled by the automatic pipe rolling machine, the uneven longitudinal and transverse wall thickness of the steel pipe basically retains the uneven distribution characteristics of the perforated capillary wall thickness. . That is, the uneven spiral wall thickness still exists in the steel pipe after rolling, and the uneven transverse wall thickness increases significantly.

We performed Fourier transform on the measured wall thickness data of the 400mm automatic pipe rolling unit, piercing, secondary piercing (extension), automatic pipe rolling, and uniform pipe rolling, and obtained quantitative analysis and analysis of uneven wall thickness. The reasons for its formation, and based on this, methods to improve the uneven wall thickness of steel pipes are proposed:

①After the secondary perforation (extension), the uneven distribution of spiral wall thickness on the waste pipe is retained until the finished pipe. Therefore, improving secondary perforation (extension) is a key link in improving the wall thickness accuracy of finished pipes. The main measure is to improve the tool design and improve the concentricity of the mandrel and head with the hole profile line when rotating.
② It is an important link to improve the uneven capillary wall thickness after perforation. The main measures are to improve the uniformity of heating of the tube blank, improve the accuracy of the centering hole, lengthen the uniform belt length and reverse cone length of the ejector, and increase the distance between the ejector rod and the ejector rod. plug. Concentricity with the rolling line during rotation.
③Although serious symmetrical wall thickness unevenness will occur during pipe rolling, it has a certain effect on reducing spiral wall thickness unevenness. Therefore, the pipe should be rolled in two passes, and the waste pipe should be turned over 90° between passes.
④The leveling process can basically eliminate symmetrical wall thickness unevenness, but it has little effect on eliminating spiral wall thickness unevenness. Therefore, the ability of the leveling machine should be improved.
⑤ Fourier transform is an effective method to study uneven wall thickness in the cross-rolling process. This method can also be used to study uneven wall thickness in other steel pipe production units.

The reasons for uneven wall thickness of automatic pipe rolling machines are:

①The existence form and severity of uneven wall thickness of perforated capillary tube directly affect the existence form and severity of uneven wall thickness of rolled steel pipe.
② When rolling pipes on an automatic pipe rolling machine, due to the bending of the ejector rod, the position of the plug head deviates from the center of the hole shape, resulting in uneven wall thickness. The wall thickness unevenness gradually increases from the pipe end to the pipe head. Therefore, reducing the residual curvature of the ejector pin and reducing the axial force of the ejector pin during pipe rolling has a significant effect on reducing uneven wall thickness. .
③The greater the amount of wall reduction, the more serious the uneven wall thickness of the unused pipe. When the wall thickness reduction is small, the automatic pipe rolling machine has the effect of reducing the uneven wall thickness of the perforated capillary tube.

④ If the hole shape is not adjusted correctly and the roll gaps are not parallel, the uneven wall thickness of the waste pipe will be aggravated.