Development of Finite Element Analysis Model for Plug Mill Rolling

In the seamless pipe rolling process, the pipe wall thickness is largely determined at the mandrel mill or plug mill. It is possible to obtain the target thickness at these mills by defining the gap of a grooved roll and an inside tool such as a plug. However, the thickness of the free deformation part, which is not in contact with the roll and tool, had generally been estimated by experimental techniques. Although a number of analytical studies of mandrel mill rolling had been reported, few reports had examined plug mill rolling. Therefore, in this research, a finite element analysis model for plug mill rolling was developed by extending the rigid plasticity finite element model "Computational Rolling Mill (CORMILL)." Good agreement between the calculated results and experimental results was obtained for the wall thickness, and it was found that the thickness of the flange part decreases with reduction of the wall thickness at the grooved bottom. These results suggested that the wall thickness distribution of rolled pipes can be controlled by using a suitable inside tool and roll shape in each rolling pass, and the necessary shapes can be obtained by using the newly-developed model.