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The main parameter that determines the quality of rolled products is the accuracy of geometric dimensions. The accuracy of the pipe wall thickness is characterized by the nominal value and the range of permissible values, i.e., the tolerance range. To obtain the nominal values of the pipe wall thickness in the rolling mill, the same roll profile (groove system) and a limited pool of diameters of cylindrical mandrels are used. Based on the diameter of rolling mandrels selected from the existing database and the need to obtain the nominal thickness of the pipe wall, the position of the rolls in the stands of the finishing group is determined, which determines the actual accuracy of wall thickness. The article presents an algorithm for calculating the rational diameters of cylindrical mandrels and provides some results of pilot testing of this technical solution. [ABSTRACT FROM AUTHOR]

The main trend in the world's pipe rolling production is the use of a continuous longitudinal rolling mill in a pipe-rolling line. In such mills, shells are rolled into pipes using long cylindrical mandrels, which are subject to severe temperature and force conditions. In addition, mandrels are the most expensive tool of continuous mills. The wear of mandrels during rolling, producing different wall thickness with a mandrel of the same diameter, and producing the same wall thickness with mandrels of different diameters necessitate adjusting the position of the rolls in the mill stands. The adjustment of the position of the rolls in the stands of a mill is known to lead to changes in the wall thickness and the formation of defects on the surface of the mother pipe, which affects other parameters of the process. This necessitates experimental study into the process of longitudinal rolling of pipes in order to evaluate the effect of the mandrel diameter on the accuracy of pipes, the angle of contact between the mandrel and the metal, and the overfill of the groove. The defects caused by the irrational choice of the diameter of a cylindrical mandrel are characterized. Lead was used as a model material for making samples during the study. [ABSTRACT FROM AUTHOR]