FEM-Based Comparison of Mandrel Wear Resulting from Elongation of Pipes Manufactured from Various Materials on a Two-Roll Screw Rolling Mill

The present article discusses the cylindrical mandrel wear change during rolling using MISIS - 130 D mill depending on the type of rolled billets materials used. The research on the mandrel wear of the screw rolling mill during pipes elongation was carried out using the finite element method (FEM). The results of the wear modeling showed that the depth of the metal removed on the mandrel surface during stainless steel pipes elongation was higher as compared to alloyed and carbon steel pipes. The significant wear of the mandrel during stainless steel pipe rolling can be explained by the rise in the applied metal force resulting from the introduction of alloying components such as chromium and nickel into rolled billets materials. Consequently, the obtained modeling results can allow predicting the service life of working tools.

Seamless Pipes Manufacturing Process Improvement Using Mandreling

The paper discusses the specific aspects of hot rolled seamless pipes manufacture using pipe rolling plants including screw-rolling mills. The method of accuracy enhancement of pipe dimensions, as well as external and internal surface quality improvement, is proposed. The article specifies the results of computer and physical modeling of the pipes mandreling process. The application of the mandreling process within the cage using different diameter mandrels is shown. We managed to decrease the typical mark caused by the metal deformation, due to the screw-rolling mill and to manufacture pipes with more accurate dimensions, as a result of the mandreling process modeling. The results of the physical experiment on mandreling the shell pierced at the screw-rolling mill showed a positive effect from the process of hollow billet cold treatment using the mandrel.

SCREW ROLLING OF PIPES IN A FOUR-HIGH ROLLING MILL

A model of four-high screw rolling mill was developed and manufactured with the help of additive technologies. The work rolls are installed: the main ones – by cup-shaped scheme and auxiliary – by mushroom scheme with an angle of rolling of ±7 degrees, with an unregulated feed angle of 15 degrees. The main and auxiliary rolls have a barrel length of 70 mm. Diameter of the main rolls in pinching is 50 mm, of auxiliary rolls – 36 mm. At the exit in cross section of the tube outlet from the rolls, their diameters are almost the same and are 72 mm. Each of the four rolls is driven by an individual drive with a 100 W motor-reducer and a rotational speed of 60 rpm by a mushroom scheme and of 83 rpm by a cup-shaped one, which minimizes the divergence of peripheral speeds in the deformation zone at different roll diameters. On the developed model of four-high rolling mill, rolling of liners from plasticine with a diameter of 25 mm with a wall thickness of 7.5 was carried out; 5.5 and 3.5 mm, corresponding to the ratio of diameter to wall thickness 3; 5 and 8. Pipe rolling was carried out on floating mandrels with diameters of 9, 13 and 17 mm. After rolling, measurements of the diameter and wall thickness of the pipes were carried out in 5 cross sections that were equally spaced from each other. In each cross section, the diameter was measured at 5, and the wall thickness at 10 points. The finite element method has been used to simulate the process of rolling these pipes in the QForm program. Assessment of the model adequacy was carried out by comparing the size of pipes and their accuracy after rolling with the results of computer simulation. When rolling at a four-high rolling mill, the wall thickness is significantly reduced.