Causes of Porosity Defects

During the welding of spiral steel pipes, gas voids can exist on or in the weld surface. This imperfection is known as porosity. The main reasons for porosity defects stem from inadequate surface preparation of the weld, where moisture or rust residues are present. During the welding process, due to the high temperatures generated by electric welding, impurities such as moisture begin to evaporate. However, because the evaporation of moisture or rust is relatively slow, cavities form within the molten metal. These cavities constitute the gas defects during welding. Especially during the groove welding process, inadequate cleaning of the groove can more easily result in the formation of gas defects. The existence of gas defects seriously impacts the welding quality of the weld, as it reduces the volume that should be welded, causing the weld metal to incompletely fill the weld seam. Consequently, the strength of the weld decreases, which can readily lead to weld cracking.