Numerical Simulation And Spread Analysis For MPM Retained Mandrel Continual Tube Rolling Process

Seamless tube is one of the important raw materials in the national economy construction. MPM(Multi-Stand Pipe Mill) retained mandrel continual tube rolling mill has been the mainstream mill type of the hot rolling process for seamless steel pipes, and its production capacity and product quality directly affects seamless steel pipe production capacity and international competitiveness of our country.Currently, many companies have to increase the size of the product,reduce production costs and improve product quality to gain market competitiveness. Therefore, to analyze MPM rolling process and the broadened research, is of great practical value,for further analysis of steel rolling forming regularity, forecasting product dimensional accuracy and performance, is of great significance, to provide reference for further optimization of device parameters and improve product quality.Based on the practical rolling process of a certain factory, a three dimensional thermal-mechanical coupled finite element model of MPM was established in this paper, using the finite element software Marc. An experiment is completed based on the MPM equipment and experimental material which is billet tube. The tube outline size and rolling force were measured. Then, the simulated results were compared with measured date.The results show that the relative error of outer diameter is 0.22%, the relative error of thickness is 3.3%, the maximum error of the mean rolling force is 4.79%. The finite element model is verified to correct.The simulation results were comprehensively analyzed, including the tube shape through each roll, the temperature variation during rolling process, the stress and strain situation, and mantel flow law. The influence on rolling force and rolling torque for roller parameters(main radius of roller pass, eccentric of roller pass, radius of roller), friction coefficient(roller friction coefficient, mandrel friction coefficient), speed schedule(roller rotation speed, mandrel speed) were researched.Pass design is the core technology of milt-stands pipe mill. The spread of tube plays an important role in the pass metal cross section area calculation(which is an important part of pass design). Based on continual rolling model of different pass and different specifications, the steel tube spread rule, including the effect of elongation coefficient and void fraction on perimeter coefficient, the effect of elongation coefficient and reduction in diameter on wall thickness coefficient, and the effect of roller speed on perimeter coefficient and wall thickness coefficient, was studied in this paper.