CO2 gas welding and assembly of bevel form of more stringent requirements. Butt weld groove forms and dimensions include angles, blunt edges and assembly space. Bevel angle mainly affect whether the arc can penetrate to the root of the weld, so that the root penetration, and then get a good weld and welding quality. Ensuring the arc able to dive into the root of the weld premise due minus mouth small slope angle. The size of the blunt edge of the depth of penetration can directly affect the roots, blunt edge, the more difficult penetration. Blunt side of a small or no blunt edge for easy penetration, but the assembly gap is large, easy to burn.

Welding current is a major factor in determining the depth of penetration, when the welding current is too large, it is easy to burn the back seam, undercut, weld, and even severe spatter and porosity and other defects; current is too small, prone to incomplete fusion , incomplete penetration, slag and other defects forming bad. Test showed that: elected with a diameter of 1.2mm wire, the back side welding welding current is 85 ~ 100 A more appropriate. Thus, the size of the welding current has a direct impact of the forming and welding defects of the weld. In the case of short circuiting transfer arc voltage increases the arc length increases. When the arc voltage is too low, the wire will be inserted into the bath, the arc becomes unstable.

So be sure to choose the right arc voltage, welding current is usually small, the arc voltage low; current, the arc voltage. When the wire diameter, welding current and voltage is constant, penetration, weld width and height than with the increase of welding speed increases. If the welding speed is too fast, easy to damage the protective effect of the gas, the weld cools too fast, bad weld; welding speed is too slow, the weld width increased significantly, the heat bath too concentrated, easily burn or produce weld.

CO2 gas shielded arc welding pipe is open arc operation, good visibility of the pool, easy to grasp changes in the bath can be directly observed arcing melting hole, it is possible to control the size of the melt hole and consistent than manual in this regard superior multi-arc welding. In addition, the welding joints less difficult to produce defect, but improper operation also prone to defects. Therefore, special attention should be operating.

Stem elongation stability of the welding process is relatively large, the longer elongation when dry, the resistance value of the wire is increased, the wire segments from overheating melting, resulting in unstable welding process, splatter serious, do not weld good and gas protection of the weld pool is not good; if the dry stretch through short, the welding current is increased, shortening the distance between the nozzle and the workpiece, the welding line of sight is not clear, could easily lead to poor bead formation, and so that the nozzle overheating, causing spatter stuck or clogged nozzles, thus affecting the gas flow. Thus, dry elongation ten times the wire diameter generally choose the best dry elongation.

For the backing welding of erw steel pipe,joints should be minimized, if required connectors, wheels for grinding into the crater site gentle slope shape. When sanding be careful not to damage the edge of the groove, resulting in a partial widening gap welded to backing weld difficult. When fitting the top slowly dry elongation aligned welding when the arc burned to the gentle slope of the thinnest position, normal swing. Welded joints manner SMAW joints CO2 gas shielded arc welding is completely different. When manually welded joints, when the arc melt burn hole, down the arc, pause to connect; and CO2 gas shielded arc welding just normal welding, with its depth of penetration can be connected to the joint.