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Causes of automatic hot rolling machine occurrence uneven wall thickness of seamless pipe
- Dec 08, 2017 -

According to the anatomical analysis of the seamless steel pipe after the hot rolling mill, it is considered that the uneven distribution of the wall thickness of the perforated capillary tube is basically retained in the form of the pipe rolling by an automatic pipe mill, which means that the wall thickness of the steel tube is still uneven and the transverse wall thickness is not all increased obviously. The reasons for the uneven wall thickness of the automatic pipe hot rolling mill are: ①The existence form and severity of the perforated pipe wall thickness will directly affect the uneven thickness of the steel tube after hot rolling. ② During process of seamless pipes on automatichot rolling machine, due to the top bar bending,the head position deviated from the hole-type center, resulting in uneven wall thickness, the maximum wall thickness and the minimum wall thickness position of the tube and the cross-section of the pipe head are almost fixed, and wall thickness of the tube end to the pipe head is gradually increased, so reduce residual curvature and axial force of the top bar has a significant effect on reducing the uneven degree of wall thickness.③ The larger reduction to the wall thickness,the more serious uneven the wall of the tube, the smaller reduction to the wallthickness, the more the automatic pipe hot rolling mill has the effect of reducing the  uneven wall thickness.④ hole type adjustment is not correct, when the roller seam uneven, the wall thickness of the pipe will increase.

Baogang group makes a Fourier transform of the measured wall thickness data of the φ400mm automatic rolling mill unit, perforation, two times perforation (extension), automatic rolling pipe and 4 rolling process, and obtains the quantitative analysis of wall thickness uneven and its forming reason. Based on this, the ways to improve the uneven thickness of steel pipe are put forward. The distribution characteristics of the spiral wall thickness uneven on the ① two times perforation (elongation) are kept to the finished pipe, so the improvement of two perforation (elongation) is the key link to improve the precision of the finished pipe wall thickness, the main measure is to improve the tool design, Increase the concentricity of the top bar and the head in the rotation process with the rolling line. ② improving the wall thickness of the capillary after perforation is an important link, the main measures are to improve the heating uniformity of the tube billet, to improve the precision of the centering hole, to increase the length of the head and the length of the back cone, and to improve the concentricity of the top rod and the head in the process of rotation with the rolling line. Although the ③ rolling pipe will produce serious asymmetry of the wall thickness, it has a certain effect on reducing the wall thickness of spiral shape. Therefore, the rolling pipe should be rolled in two ways, the road between the pipe should be overturned 90 °. The ④ process can basically eliminate the symmetry wall thickness uneven, but to eliminate the spiral wall thickness uneven effect is very small, therefore, should improve the ability of the whole machine. ⑤ Fourier transform is an effective method to study the uneven wall thickness in skew rolling process, which can also be used in the study of wall thickness uneven of other pipe production units.