Features and key operating points of CO2 shielded welding

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Carbon dioxide shielded welding is the full name for arc welding protected by carbon dioxide gas. The shielding gas is carbon dioxide (sometimes a mixture of CO2 and Ar), primarily used for manual welding. Due to the special effects of the thermophysical properties of carbon dioxide gas, when a conventional welding power source is used, it is not possible for the molten metal at the wire tip to form a balanced axial transition; as a result, short circuits and droplet necking occur, which leads to more spatter compared to the transition process in MIG welding. However, by using a good welding machine and selecting appropriate parameters, a very stable welding process can be achieved, which reduces spatter. Due to the low cost of the shielding gas used, good weld shape is obtained when short-circuit transfer is employed; furthermore, the use of wire containing deoxidizers enables the creation of high-quality weld joints free from internal defects. Therefore, this welding method has become one of the particularly important welding methods for ferrous metal materials. CO2 shielded welding uses CO2 as a shielding gas to isolate the air; its concentration must be 95.5% with a water content of less than 0.05%. During welding, the wire melts when an electric current is applied, and this process falls under the category of arc welding. Features of CO2 shielded welding: 1. High production efficiency. Due to the high current density in CO2 welding, the heat from the arc is utilized more effectively, and there is no need to remove slag after welding; hence, it offers higher productivity compared to manual arc welding ； 2. Low cost: CO2 gas is inexpensive, and power consumption is low, reducing costs ； 3. Minimal welding deformation: The arc heat in CO2 welding is concentrated, resulting in a small heating area of the workpiece, and thus minimal deformation ； 4. Good welding quality: CO2 welding produces welds with low hydrogen content, good crack resistance, and excellent mechanical properties of the welds ； 5. It is easy to operate; during welding, the arc and molten pool can be observed, making it difficult to weld off-course. It is suitable for welding in all positions and is easy to master. Key points for CO2 shielded welding: 1. For joints with grooves in a vertical or inclined position, welding should be carried out from bottom to top; for thin-plate butt welds and fillet welds without grooves, welding can be done from top to bottom ； Leftward welding method can be used for vertical, horizontal, and overhead butt joints. Image 2. When working outdoors and the wind speed is greater than 1 m/s, wind protection measures should be taken. 3. A suitable welding sequence must be selected based on the structure of the workpiece to be welded. 4. Appropriate-sized arc-starting and arc-extinguishing plates should be installed at both ends of the connection. 5. The dirt inside the hose and the splashes from the nozzle should be cleaned regularly. 6. For grooved joint seams, especially multi-pass welds on thick plates, the welding wire should pause slightly on both sides of the groove while being moved; the zigzag motion of the wire should result in a layer thickness of no more than 4 mm, so as to ensure good weld fusion.