Prediction and control of springback in setting round process for pipe-end of large pipe

• A quantificationally analytical method for the circle–oval process is built.
• The meshing idea in the finite element theory is used in the analytical method.
• A two-step control strategy is built, which can control the ovality within 0.5%.
• An equivalence relation and a similarity relation are given to support the strategy.

The setting round process for the pipe-end of LSAW (Longitudinal Submerged Arc Weld) pipes is one of the most important processes to assure the pipe quality. The process is a local elastic–plastic deformation process. Therefore, it is difficult to provide a quantificational analysis because of the influence of its rigid part. However, the springback law of the circle–oval process for the whole pipe can be easily predicted. First, the equivalence relation between the setting round process and the circle–oval process, and the similarity relation in the circle–oval process between the pipe-end and the short pipe are studied. Then the quantitative analysis of the circle–oval process of short pipe and its springback process is given, and experimental results match with the theoretical results. Finally, the two-step control strategy of pipe-end setting round process is established, and experimental studies show this strategy can control the residual ovality within 0.5%.