Application And Progression Of Analytic Technology For Seamless Steel Pipe Rolling Processing

The analytical technique of seamless steel pipe rolling has been widely used in finite element method (FEM) since the late 1980s. Recently, with the development of computer output, the analytical technique has evolved from two-dimensional to three-dimensional advanced deformation analysis. As a result, the dimensional accuracy and quality of steel pipe products and even welded pipes such as erw steel pipes have been improved. The representative analytical techniques are described below.

1. Extension rolling analysis technology
The mandrel mill uses mandrel and orifice rolls for rolling, so unlike plate rolling, there is a free deformation zone in the roll circumferential direction where the rolls do not contact the mandrel. Since the free deformation zone is rolled on the next frame, it is important to predict the deformation including the free deformation zone in order to correctly understand the integrated characteristics of the mandrel mill.

This complex deformation prediction cannot achieve high accuracy using the conventional cache implementation algorithm, and therefore requires high-precision analysis. Taking into account the shear deformation in the rolling direction, an approximate three-dimensional analysis is performed using ordinary expansion plane deformation analysis. The results show that the calculated values ??are in good agreement with the experimental values.

Recently, with the development of computer technology, the development of full three-dimensional finite element method analysis technology has been accelerated. It can also be used to analyze the influence of the tension between the frames and to analyze the speed difference between the rollers and the tube blanks.

2. Sizing rolling analysis technology

Since there is no tool on the inner surface when sizing rolling, the shape of the inner surface of the rolled material is not neat when rolling the thick-walled tube. When a three-roll mill is used, the inner shape of the rolled material is hexagonal. Through the analysis of the three-dimensional finite element method, the occurrence mechanism of the inner surface corner phenomenon and the countermeasures to be taken are clarified. 

A substantially uniform wall thickness can be obtained when using an aperture pattern with an ellipticity of approximately 0.986 which is close to a perfect circle, but a clear internal surface hexagonal corner is formed when a pattern having an ellipticity of approximately 0.960 which is close to a perfect circle is used. This analysis can predict the change in wall thickness during rolling with a stretch reducer, and clarify the effect of roll profile characteristics and the tension between the frames on the internal hexagonal corners.