Cause of Porosity Defects

During the welding process of spiral steel pipes, gas spaces may exist on the surface of the weld or within the weld, and this defect is known as porosity. The main cause of porosity defects is due to unclean surface treatment of the weld, with the presence of moisture or rust. During the welding process, under the influence of high welding temperatures, impurities such as moisture begin to evaporate. Due to the slow evaporation of moisture or rust, cavities form in the molten metal, and these cavities constitute gas defects in the welding process. Especially during bevel welding, incomplete cleaning of the bevel can more easily lead to the formation of gas defects. The presence of gas defects will seriously affect the welding quality of the weld, as it reduces the volume that should be welded, causing the welding metal to not completely fill the weld, which decreases the strength of the weld and easily leads to weld cracking.