ELECTRODE WIRE FOR CO2 WELDING

CO₂ welding wire must have a special composition to withstand the oxidising nature of the CO₂ arc atmosphere. Though, CO₂ is not reactive at room temperature, but at the high temperature of the arc it is dissociated into carbon monoxide and atomic oxygen.

CO₂ = CO + O

Under these oxidising conditions, the carbon present in an unkilled weld pool would react with the oxygen and form carbon monoxide and thus form porosity. To prevent this from happening additions of deoxidisers are made to the CO₂ welding wire to lock up the oxygen. Most CO₂ welding wires are therefore added with silicon and manganese. The silicon and manganese remove the oxygen as a slag, which floats to the surface of the weld. Some wires also contain small additions of other deoxidisers such as aluminium, titanium and zirconium.

Solid wires for CO₂ welding are commonly available in diameters of 0.8, 1.0, 1.2 and 1.6 mm. The choice of wire diameter for a particular application is extremely important since this decides the current range which can be used and the ease with which the welder can control the weld pool. The most commonly used wire sizes are: 0.8 mm for sheet steel. This allows low current to be used. 1.2 mm wire for thicker material. This diameter is versatile since, at low wire speeds, it can be used down to 80 A for the welding of sheet metal or the positional welding, Whereas at higher wire speeds currents up to 350 A can be used to give high metal deposition rates and deep penetration.