1. The characteristics of the arc are unique (1) the effect of the weld quality and high melting slag isolation air protection is good, the main component of the arc area is CO2, the nitrogen content and oxygen content in the weld metal are greatly reduced, the welding parameters are automatically adjusted, the arc walking mechanization, the weld pool has long time, the metallurgical reaction is full, the wind resistance is strong, so the weld composition is stable and the mechanical properties are good. (2) the working conditions are good, slag arc isolation is conducive to welding operation; mechanized walking, low labor intensity. 2. The electric field strength of the arc column is higher than that of the gas shielded arc welding. (1) the equipment has good regulation performance. Because of the high electric field intensity, the sensitivity of the automatic regulating system is high, and the stability of the welding process is improved. (2) the lower limit of welding current. 3. The high efficiency of the welding wire is due to the shortening of the wire’s conductive length and the increase of the current and current density, which greatly improves the penetration ability of the arc and the melting rate of the wire, and the total thermal efficiency is greatly increased because of the heat insulation of the flux and slag, and the welding speed is greatly improved.