Elaboration of a mathematical model and a computer program for calculation of energy-power parameters of reduction process of continuously casted billets at three-roll screw mills

For production seamless hot-rolled pipes, round continuously casted billets (CCB) are used, the diameter of which is restricted by the limit sizes of CCM moulds. The expansion of billets assortment necessary to provide pipe-rolling lines (PRL) by required diameters is possible through preliminary reduction of CCB, which is made mainly at three-roll screw-rolling mills having powerful drives. If a plant has no such mills, billets reduction can be accomplished at existing three-roll Assel’s mills being comprised by various PRLs. However, the possibilities of such mills are restricted by acceptable current loads for their drives, since they are designed to roll out pierced pipe stock, but not to reduce solid billet. To determine energy-power parameters of the process of pipe billet reduction at three-roll Assel’s mills, a mathematical model was elaborated accounting geometric, temperature, kinematic and deformation peculiarities by determination the volume of accumulated metal at each roll before rolling out, section of forming diameter of reduced pipe billet and temperature variation during the reduction. As a result, the software product “Reduction Motor Load 2020” (RML2020) was elaborated, which includes a computing kernel based on the elaborated mathematical model for determining the power parameters of the reduction process and a module for analyzing the initial data with a system of boundary conditions. The interface of the software product allows displaying the results of calculations and analysis both in numerical form and in the form of graphs. The elaborated software product contains a database of the main steel grades and allows calculating the current loads on the Assel’s mill drives during the reduction of billets made of various steel grades. The software allows also to accomplish analysis of the acceptable values of various initial parameters (diameters of the initial and reduced billets, temperature of the initial billet, feed angle and rotation frequency of rolls) to ensure the operation of the mills in the acceptable range of current loads. There is also a possibility of making a report in the form of an Excel document and collecting statistical data on the actual values of current loads. By application the RML2020 program, acceptable reduction modes of a pipe billet made of 15Х13Н2 steel (AISI 414) with a diameter of 156 mm into a billet with a diameter of 120 mm were calculated for screw Assel’s mills of PTL-1 of JSC VTZ.