Finite element simulation of pipe straightening in a 3-pair cross roll machine with symmetrical and asymmetrical profiling of the outer rolls

Abstract

To enhance competitiveness of domestic metal products, in particular, pipes, it is necessary to ensure their compliance with international standards on basic quality indicators. The pipe straightening process provides such quality indicators as straightness and crosssectional shape. Cross roll pipe straighteners are the most common and most effective machines for straightening pipes of small and medium diameters. Six-roll (3-pair) pipe straighteners with special roll profiling are the most modern machines, they provide two types of straightening: in the groove of profiled rolls and at the pitch between the roll cages. However, the lack of knowledge about the forming process regularity is holding back the widespread introduction of such machines. The finite element model has been developed in the work, and with its application it has been studied how straightening process parameters in profiled rolls with symmetrical and asymmetrical profiling of the outer rolls pairs affect the indicators of pipe straightening and straightening force. Based on the results of their implementation, it is found that straightening in the groove and at the pitch makes it possible to reduce almost three times the residual curvature of the pipe, with the overlap of the middle rolls relative to the outer ones being 2.5 times smaller. At the same time, the force on the most loaded middle rolls has increased almost twofold, which should be taken into account considering the potential out-ofroundness of the thin wall pipe section. The use of additional asymmetric profiling of the outer rolls with pitch adjustment has virtually no effect on the quality of straightening in the groove, increases the quality of straightening at the pitch by up to 15% with a 5-7% decrease of the maximum straightening force. The developed finite element model allows determining the rational values of the roll overlaps to ensure the minimum residual curvature of the pipes.