Welding spatter formation and elimination tips

Basic knowledge about welded pipe

In the welding process, molten metal particles and slag will fly around. The spatter in welding process is about short circuit splash, gas precipitation splash, free transition splash.

The spatter caused by electric explosion is normal short-circuit spatter, which is very small under small current. When the current is large, it will cause large electric explosion spatter, resulting in instantaneous short circuit and small loop inductance, which is easy to cause strong spatter of droplet and molten pool.

Under the condition of high current, thick welding wire and low voltage, the short circuit phenomenon occurs, and the molten steel in the molten pool will form spatter. Too fast arc striking or wire feeding will cause solid short circuit between the welding wire and the molten pool, and the welding wire may be broken by sections, causing spatter.

In the free transition, the CO2 arc shrinkage is concentrated at the bottom of the droplet, which causes the droplet to deviate from the wire axis, and the fine neck between the droplet and the welding wire explodes with a large current, causing splash.

Causes and reducing measures of spatter in CO2 welding

Spatter is one of the main technical problems in CO2 welding. There are two ways to produce spatter, one is caused by short-circuit small bridge electric explosion, the other is caused by metallurgical factors.

According to the test, when a large current passes through the short-circuit bridge, the short-circuit bridge will overheat and explode, forming spatter. This electric explosion spatter occurs between the welding wire and the droplet in the normal short-circuit (short-circuit time is more than 2 ms). When the bridge is damaged, a large amount of liquid is pushed to the molten pool, and only a small amount of small droplets become spatter. When the peak value of short-circuit current is small, the spatter is small, and vice versa, The spatter is large.

In the instantaneous short circuit, there is a short-circuit bridge between the droplet and the molten pool. The overheated explosion of the bridge will throw the metal droplet to the four sides and produce spatter, which will adhere to the surface of the workpiece and damage the surface finish of the workpiece. The way to reduce the spatter is to avoid the instantaneous short circuit, reduce the current in the early stage of the short circuit, reduce the current speed, and reduce the short-circuit current in the later stage, The small bridge is pulled off by the tension of the metal surface to reduce the spatter.

Another kind of spatter caused by gas escape explosion is related to welding metallurgy process. Deoxidized welding wire or welding wire containing aluminum and titanium can be used to reduce spatter, which can inhibit the formation of CO gas. Attention should be paid to the cleaning of welding wire and workpiece surface.