Main Factors Affecting the Welding Quality of CO2 Welding

Wire Extension length

The length of the welding wire extending from the contact tip is the wire extension length. In general, the pole extension length should be 10-15 times of the welding wire’s diameter, that means: L=(10-15) d. When standardized, slightly larger. Standardized hours, slightly smaller.

Wire extension too long: When the welding wire extends too long, the resistance heat of the welding wire increases, the melting speed of the CO₂ welding wire accelerates, and it is easy to cause the welding wire to melt in sections, with large splashing, shallow melting depth, and unstable arc combustion. At the same time, the gas protection effect is not good.

Wire extension too short: the contact tip is easy to burn. At the same time, the contact tip heats up and is prone to wire jamming. Splashes can easily clog the nozzle and result in too deep molten depth.

Table 1 Relationship between Current and Rod wire extension length

Gas flow rate

Gas flow rate L=[(10-12) d] L/min

Too big: generates turbulence, causing air infiltration and creating pores, especially for gas sensitive materials such as aluminum alloys, magnesium alloys, etc., which are generally internal pores

Too small: Poor gas protection (refer to the extreme condition where there is no protective gas, which can easily lead to honeycomb like pores).

It is not affected when the wind speed is ≤ 2m/s.

Measures should be taken when the wind speed is ≥ 2m/s.

① Increase the gas flow rate.

② Take windproof measures.

Attention: When gas leakage occurs, it will cause porosity in the weld seam. The leakage point must be treated and cannot be supplemented by increasing the flow rate. Pores cannot be repaired without removal, and will only increase with welding.

Arc force

When different plate thicknesses, positions, specifications, and CO₂  welding wires are used, different arc forces should be selected.

Too big: hard arc and large splashing.

Too small: Soft arc and small splashing.

Compression force

Tight: The CO₂ welding wire is deformed, the wire feeding is unstable, and it is easy to cause wire jamming and increased splashing.

Loose: Welding wire slips, wire feeding is slow, welding is unstable, and it can also cause splashing

Current and voltage

The empirical formula for the relationship between CO₂ welding current and CO₂ welding voltage in gas shielded welding is U=14+0.05I ± 2

The welding current should be selected correctly based on the thickness of the base metal, the form of the joint, and the diameter of the CO₂ welding wire. During short-circuit transition, while ensuring CO₂ welding penetration, try to choose a low current as much as possible, because when the current is too high, it can easily cause the pool to roll, resulting in large splashes and poor molding.

The welding voltage must be well coordinated with the current. Welding voltage that is too high or too low can cause splashing. The welding voltage should increase with the increase of welding current and decrease with the decrease of welding current. The optimal welding voltage is generally between 1-2V, so the welding voltage should be carefully adjusted.

Current too high: arc length, large splashes, a tactile sensation, excessive excess height, poor fusion on both sides.

Voltage too high: long arc, slightly large spatter, unstable current, insufficient residual height, wide weld joint, easy to burn the conductive nozzle during arc ignition.

The influence of welding speed on CO₂ welding

The welding speed has a significant impact on both the internal and external quality of the weld seam. When the current and voltage are constant:

Welding speed too high: Decreased melting depth, melting width, and excess height, resulting in convex or hump weld beads, and biting of the weld toe. When the welding speed is too fast, it will damage the gas protection effect and easily produce pores.

At the same time, the cooling rate of the welded joint will also be correspondingly accelerated, thereby reducing the plasticity and toughness of the welded metal. And it will cause an edge to appear in the middle of the weld, resulting in poor molding.

Welding speed too low: The molten pool becomes larger, the weld bead becomes wider, and the weld toe overflows. Slow welding speed can easily release gases from the molten pool. Due to overheating, the weld metal structure may become coarse or burn through.

The selection of CO₂ welding parameters should be based on the following conditions: the appearance of the weld seam should be beautiful, and there should be no defects such as burn through, undercutting, porosity, cracks, etc. Control the melting depth within an appropriate range. The welding process is stable with minimal spatter. I heard a rustling sound while welding. At the same time, it should have the highest productivity.