Phenomenon: The gas absorbed in the weld metal melted during the welding process cannot be discharged from the molten pool before cooling, and remains in the weld to form a cavity. According to the position of the pores, the inner and outer pores can be divided. According to the condition and shape of the pores, the presence of the pores in the weld will reduce the weld strength, stress concentration, and low temperature brittleness and hot cracking tendency.

Control Measures: Select qualified welding rods, and do not use welding rods with cracked, peeled, deteriorated, eccentric or severely corroded cores. Clean oil and rust spots near the welds and on the surface of the welding rods. The size of the current should be chosen to control the welding speed. Before the welding, the workpiece is preheated. When the welding is finished or stopped in the middle, the arc should be slowly evacuated, which is beneficial to slow down the cooling rate of the molten pool and the gas in the molten pool to avoid the occurrence of porosity defects. Reduce the humidity at the welding operation site and increase the temperature of the operating environment. In outdoor welding, if the wind speed reaches 8m/s, rainfall, dew, snow, etc., it is necessary to take effective measures such as windshield and rain canopy before welding.