1. Expression form of pore defect
During the welding process, the gas in the molten pool does not escape in time, and the holes remaining in the weld are pore defects, as shown in the figure. In terms of shape, there are spherical stomata and striped stomata; In terms of quantity, there are single stomata and group stomata. Among them, group stomata can be divided into dense stomata and chain stomata. Some pores are produced on the weld surface, while others remain inside the weld. The harm of pore defect is as serious as slag inclusion defect, which needs the attention of welding operation and quality inspection personnel.
2. Main measures to prevent pore defects
In order to prevent the occurrence of pore defects, the following measures need to be taken:
① Firstly, the invasion of gas should be reduced. The groove of large steel castings should be cleaned and polished within 20 mm ~ 30 mm around the groove to ensure that it is metallic luster and free of impurities such as oil rust. If necessary, the water at the groove can be evaporated by preheating before welding before welding;
② The quality control of welding materials shall ensure that the welding materials are dried and stored according to the requirements of welding process, and the plug-in insulation barrel shall be used in the process of welding to avoid the damp of welding rod;
③ When using gas shielded welding, pay special attention to the inspection of welding gun, nozzle and gas pipeline to ensure that the welding equipment meets the requirements. In addition, special attention should be paid to the wind protection of the surrounding environment of the welding work area. Excessive wind speed can easily lead to the instability of the shielding gas in front of the welding gun nozzle into a turbulent state, thus losing its protective effect.