Where Does Weld Spatter Come From?
A very common occurrence in gas metal arc welding (GMAW) is the creation of what welders call “spatter”, which is essentially little droplets of molten material that are generated at or near the welding arc. Spatter is generally regarded as a nuisance and is a critical factor that needs to be taken into consideration when developing an application.
First, let's look at some of the problems associated with spatter.
Problems Associated with Spatter
Spatter can cause a lot of problems in most manufacturing processes, the most common problems are:
- Spatter balls sticking to work pieces or tooling.
- Spatter burning workers clothing and skin.
- Loss of material from the arc and weld.
- Excessive clean up of spatter.
Most manufactures strive to reduce the amount of spatter generated, if not eliminate it all together. To eliminate a problem you have to know why the problem is occurring, in this case what causes spatter.
Where Does Spatter Come From?
Spatter is caused by several factors, the main factor being a disturbance in the molten weld pool during the transfer of wire into the weld. Typically this is caused by the relationship between amperage and voltage. This is usually seen when the welding voltage is too low or the amperage is too high for a given wire and gas combination. In this situation, the arc is too cold to keep the wire and pool molten and causes a stubbing effect of the wire. This can occur at both high and low current ranges.
Continuing on the last point, spatter may be generated as a result of the gas selected. In GMAW, the use of CO2 increases the arc energy and is very cost effective yet creates more weld spatter. Argon is commonly used to counter balance the spatter generated from CO2. Figure 1 gives a comparison of CO2 welding to MAG welding at different current levels.
Figure 1: Spatter generation comparisons for CO2 and MAG welding.
Figure 1 also shows that increasing the amperage increases the amount of spatter generated by amplifying the forces in the arc that cause spatter.
Other Spatter Generation Patterns
The following are some other patterns which result in spatter generation.
- In a short arc process, the weld droplet contacts the weld pool and scatters the base metal before fusion.
- When fusion occurs after short-circuiting and the weld bead heats due to a large increase in current. This is essentially the problem described above where the amperage becomes too excessive for the given welding wire. This is also what most welders like to refer to as the “arc explosion” or the popping that causes spatter.
- An arc repulsion force causes the weld bead to break off and scatter
- Splashing occurs when a weld droplet falls into the molten pool. This is very common in a globular transfer mode.
- When the weld bead is affected by the magnetic repulsion force of the short circuit in the weld pool.
Most of these factors can be controlled or restricted through various techniques. Recent research conducted by DAIHEN Corporation has led us to new technological developments that has greatly improved the ways of curbing welding spatter levels.
Other Factors That Influence Weld Spatter
Additionally, there are a number of other factors that can worsen spatter generation amounts. Some of these conditions are consumable related, some are torch related, and others are production environment related.
- Poor quality welding wire.
- Incorrect gas mixtures.
- Poor welding surface conditions (such as oily parts, paint, rust, etc.).
- Improper torch angle.
- Wire stick-out length.
- Grounding location.
- Wind / loss of shielding gas.
- Moisture in the atmosphere.
Usually, combinations of these factors cause an imbalance in the amperage and voltage. For example, oil on the parts being welded may cause a welding power supply to receive inconstant feed back and result in the power supply over or under compensating. To counter this, our D-Series come equipped standard with filtering systems to ensure a constant output of welding characteristics to control this relationship.
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