In the production process of ERW pipeline, as long as welding, the surface of ERW pipeline will produce stress and deformation, but to varying degrees. The welding stress and various deformation of ERW pipe during welding process often cause the quality of welding products to decline and even cause cracks. The welding deformation caused by the change of weld size and shape may be unrelated to other pipes or the processing allowance is insufficient to cut if the change exceeds a certain value. Now let's talk about pressure and deformation.


The first is the surface stress of ERW pipeline. When the material can not produce displacement under external force, its geometry and size will change. This deformation is called strain. When a material deforms, it produces the same size, but the direction of reaction force is opposite to that of external force. The distribution of internal force at the concentration point is called stress. Stress and micro-area products are internal forces, or the internal force resists the interaction between different parts of the body due to the deformation of external factors (stress, temperature change, etc.). The function of this external cause is to try to return the object from the deformed position to the pre-deformed position.


From a mechanical point of view, deformation is a change in the shape of a structure (or part of it). Any structure is made of deformable solid material, which will deform and displace under external force. In the pipeline production process, even if it can be corrected, such as mechanical or flame correction, it not only consumes time and labor, but also increases the additional stress of the pipeline, which is not conducive to the use of construction. Therefore, we must understand the causes of welding stress and deformation, size and how to reduce and avoid welding stress and deformation.