ERW pipe forming process can be divided into two phases: the first stage of deformation; the second stage for reducing distortion. In both phases, the steel pipe inner layer is always affected by the circumferential compressive stress and compressive deformation. The outer layer of fine molding of the bending process by weeks to the tensile stress and extension deformation: in the fine shaping and sizing process. Steel outer layer of compressive stress and compressive deformation. And ERW pipes of different specifications, the outer layer of the final strain differences. This shows that the ERW pipe inner and outer layers in the pipe circumferential strain is inconsistent. Stress state and stress the size of change.

Common problems in manufacturing process of ERW line pipe:
(1) ERW line pipe manufacturing process will bend uneven deformation of the pipe week up there is a large residual stress, so take the necessary measures to reduce the negative impact of residual stress on the ERW line pipe manufacturing process.
(2) the study and control of ERW line pipe residual stress should not be confined to the detection and analysis of the residual stress of the final product, required to pipe forming process of ERW pipeline analysis, taken from the perspective of process control measures to reduce ERW pipeline the residual stress of the pipe, reduce the adverse effects of residual stress may cause the quality of ERW line pipe.
(3) Sizing is mainly to ensure the pipe diameter to meet the requirements, the hydrostatic test is to ensure that the density of steel pipe, but for the ERW pipeline in terms of pipe, Is also an important process to reduce the circumferential residual stress.