# Continuous and synchronous calibration process of ovality and straightness for longitudinally submerged arc welding pipes with three rollers

## TL;DR

A new method for improving the shape and straightness of pipes during welding is introduced and tested successfully.

## Contribution

A continuous and synchronous calibration process using three rollers for LSAW pipes is proposed and validated.

## Key findings

- Residual ovality and straightness decrease with increased radial reduction and bending.
- Reciprocating bending reduces curvature differences and improves uniformity.
- Calibrated pipes achieved less than 0.2% residual straightness and 1% residual ovality.

## Abstract

A new process of continuous and synchronous calibration process of ovality and straightness for LSAW (Longitudinally Submerged Arc Welding, LSAW) pipes with three rollers is proposed. Specifically, the process is introduced from three aspects: roller-shape, loading parameters and axial and circumferential deformation paths. The process is verified by numerical simulation and physical experiments. Further, the stress-strain in the Sections Ⅱ and Ⅳ is analyzed. The relationship between the process parameters and the residual ovality and residual straightness by experiments is discussed. The calibration scheme of LSAW pipes is put forward by using the control variable method. The results show that the shear stress is the principal stress direction in the Sections Ⅱ and Ⅳ. The residual ovality and residual straightness decrease with the increase of the radial reduction and times of reciprocating bending. The reciprocating bending process can eliminate the difference of the initial curvature, make the curvature of each section tend to be uniform. After calibration, the residual straightness is less than 0.2% and the residual ovality is less than 1%, demonstrating a good feasibility of this process.