Characteristics of CO2 welding:

(1) CO2 will decompose into CO, O2 and O under the action of high temperature welding arc, which has a strong compression effect on the arc. As a result, the arc shape of the welding method has the characteristics of small arc column diameter, small arc heel area, and often difficult to cover all the droplets at the end of the welding wire. Therefore, the droplets are subjected to large transitional resistance (spot force), which makes the droplets coarser. The transition path becomes less axial and the spatter rate is larger.

(2) The welding area is well protected, the density of CO2 is the largest of the commonly used protective gases, and the volume of CO2 gas increases after heat decomposition, so the protection is better;

(3) The energy is relatively concentrated, and the penetration capacity is large;

(4) Low production cost and energy saving.

(5) The process and technology also have good visibility of the welding zone, easy to observe and operate; The welding heat affected zone and welding deformation are small. The size of the molten pool is small, the crystallization speed is fast, and the welding performance of all positions is good. Advantages of low sensitivity to rust.

Metallurgical characteristics: (1) oxidation of alloying elements when welding CO2, under the action of high arc temperature, CO2 will decompose into CO, O2 and O, under welding conditions, CO is insoluble in metal, and does not participate in the reaction, and CO2 and O have strong oxidation, so that Fe and other alloying elements oxidation. (2), deoxidation and alloying of weld metal? A certain amount of deoxidizer is usually added to the welding wire for deoxidation, in addition, the remaining deoxidizer is left in the weld as an alloying element to make up for the oxidation burning loss and ensure the chemical composition requirements of the weld.

Droplet transition: (1), short circuit transition (short arc, fine wire, small current) suitable for sheet all-position welding; (2), fine particle transition, thick wire, long arc, high current welding; (3), submerged arc drop transition (rarely used).

Scope of application: At present, CO2 gas shielded welding is widely used in locomotive manufacturing, shipbuilding, automobile manufacturing, mining machinery manufacturing and other fields. Suitable for welding low carbon steel, low alloy steel, low alloy high strength steel, but not suitable for welding non-ferrous metals, stainless steel. Although some data show that CO2 gas shielded welding can be used for welding stainless steel, it is not the first choice for welding stainless steel.