Computational simulation of continuous pipe rolling on a FQM mill in the Deform-3D program

Modern continuous mills such as PQF (Premium quality finishing) and FQM (Fine Quality Mill) are high-performance units that ensure high quality of seamless pipes of various grades. This equipment uses a long-held mandrel, which has a certain speed of movement in the center of deformation. A three-mill extractor is used to extract the mandrel at the end of the technological cycle of rolled products. It is possible to form surface defects on the draft pipe due to the high-speed and deformation conditions of this process. We set and solved the problems of numerical simulation of the continuous rolling process of pipes on the FQM mill in this paper. The solution of the problems allowed us to assess the nature of the influence of the deviation of the rolling axes of the continuous mill and it is extraction due to poor retention of the mandrel by gabions between the stands on the quality of the draft pipe. It was found that the accuracy of pipe sizes decreases with increasing deviation from the rolling axis, based on the results of numerical simulation of the continuous rolling process. When the deviation is 3 mm, the deviations in diameter and wall thickness from the nominal values are (ΔD/DN)•100 = 7,19 %, and (ΔS/SN)•100 = 19,45 %, which makes the geometric dimensions of the pipes beyond the normative values of any standard. There is an increase in the time of removing the mandrel from the pipe and peak loads on the mandrel, which may indicate that the process of removing the mandrel is not stable and its strong impact on the inner surface of the pipe. It leading to the appearance of a visible defect. The results of solving the problems allowed us to formulate technical recommendations aimed at reducing the probability of surface defects in the production of pipes at the FQM mill.