Why does CO2 welding produce spatter?

The main causes of spatter in CO2 welding include the following:

Spatter caused by metallurgical reactions: This type of spatter is primarily caused by CO2 gas. During welding, carbon in the droplet and weld pool oxidizes to CO2. Under the high arc temperature, CO2 rapidly expands and increases in pressure, causing the droplet and weld pool to explode, generating large amounts of spatter.

Spatter caused by spot pressure: This type of spatter depends primarily on the polarity of the weld. When welding with positive polarity (positive electrode connected to the workpiece and negative electrode connected to the welding wire), positive ions fly towards the droplet at the end of the welding wire, creating a strong mechanical impact and forming large particles of spatter. In reverse polarity welding, the impact force of electrons flying towards the end of the welding wire is weak, significantly reducing the spot pressure and resulting in less spatter.

Spatter caused by droplet short-circuiting: This type of spatter occurs during the short-circuit transition and is more severe when the dynamic characteristics of the welding power source are poor. When a molten droplet contacts the weld pool, if the short-circuit current increases too quickly or the maximum short-circuit current is too high, the liquid metal at the constriction will explode, generating a large amount of fine particle spatter. If the short-circuit current increases too slowly, the short-circuit current cannot reach the required value in time. In this case, the constriction cannot break quickly, causing the wire extending from the contact tip to soften and break in sections under prolonged resistance heating, accompanied by a large amount of large particle spatter.

Spatter caused by non-axial particle transfer: This type of spatter is caused by the repulsive force of the arc during particle transfer. When the droplet is pushed to one side of the wire end by the combined effects of spot pressure and airflow pressure in the arc column, it is thrown out of the weld pool, generating large particle spatter.

Spatter caused by improper selection of welding process parameters: This type of spatter is caused by improper selection of welding process parameters such as welding current, arc voltage, and loop inductance. For example, as the arc voltage increases, the arc lengthens, the droplet tends to grow larger, and irregular oscillation occurs at the end of the wire, resulting in increased spatter. Increasing welding current reduces droplet volume, increases deposition rate, and reduces spatter.

Understanding these causes can help you take appropriate measures to reduce spatter and improve welding quality and efficiency.