Study of mandrel wear during billet piercing on the MISiS-130D screw rolling mill

Piercing represents one of the key processes in the production of hot-rolled pipes on screw rolling mills due to its determinative effect on the quality of the resulting bloom. The main factor affecting the quality of hot-rolled pipes is the wear resistance of the working tool. The work equipment frequently fails due to high wear of the surface. It is known that the mandrel affects the quality of the inner surface of the resulting pipes and the accuracy of geometric dimensions. In addition, increased wear of piercing mandrels leads to a decrease in the productivity of industrial units. In this paper, the mandrel wear was studied during the piercing of billets, made of 12Kh18N10T corrosion-resistant steel, into pipes on a MISiS-130D pilot-industrial screw rolling mill. Using the SolidWorks software package, the process of piercing blanks with a diameter of 60 mm and a length of 400 mm was simulated in order to assess the wear of mandrels using the QForm software package. The modeling of piercing processes was carried out by varying the rolling conditions: rolling speed, feed angle, and ovalization factor of the deformation zone. It is concluded that the distribution of the wear value along the length of the mandrel is uneven; the dependence of the mandrel wear value on the variable technological factors of the piercing process is revealed. The dependence of the wear depth of piercing mandrels on the temperature of their working surface and the duration of rolling was studied. Methods for increasing the wear resistance of piercing mandrels based on the selection of rational rolling modes are proposed.