How Can I Reduce My Spatter? (Part 1 of 2)
By Matt Brooks
January 11, 2008
Spatter that occurs in gas metal arc welding (henceforth GMAW) applications can cause a number of headaches that range from the inconvenience of sweeping up a dirty/dust covered work cell to a full surface grind and repair welding. In the most extreme situations, weld spatter can even cause harm to welders by burning through clothing and skin. In most situations, weld spatter can typically be reduced and save a fair amount of money and time by reducing the required repairs or clean up.
This article explains some of the simple techniques used to reduce spatter, helping you create a more ideal production environment.
This is part 1 of a 2 part series.
Technique #1 - Increasing the Voltage
Increasing the welding voltage is one of the quickest and typically most effective ways to reduce spatter. The reason this works so well is that the voltage directly controls the arc length and heat input for a weld. (The same effect is accomplished by reducing the arc current. However, when the current is reduced the amount of wire put into the weld will also be reduced.)
In short arc welding, increasing the voltage reduces both the chance the wire will stub into the molten pool, as well as the number of shorts per second (both of which are causes of spatter generation). In pulse and spray welding, increasing the voltage increases the spray transfer strength, which reduces the number of shorts that may occur. Generally speaking, with spray or pulse methods, increasing the voltage reduces the droplet size since the wire is melting faster and results in a reduced driving force of each individual droplet.
Figure 1: An example of incorrect weld settings causing excessive spatter
However, the welder needs to be careful when increasing the voltage, since almost every adjustment can have negative side effects.The primary drawbacks to increased voltage are:
- Overall heat increases, resulting in a widened heat affected zone (HAZ).
- Increased occurrences of burn through.
- Decreased contact tip life.
- Welding undercut may occur.
The welder must keep a good balance between the current and voltage to create optimal welds. If these side effects occur then another method for reducing spatter may be suggested. It is also possible when changing the parameters to slip into a globular mode, which results in very large droplets that can cause excess spatter. Globular transfer is the range between short arc and spray and can easily be recognized and avoided through readjustment of the parameters.
Technique #2 - Clean the Material
Another major cause of spatter is surface contamination. This can come from rust, oils, water, paints or scale from internal elements. The contamination has two effects on the weld that create spatter. The first effect is that the contamination can cause variation in the welding feedback system, and the welding power supply may try to over compensate for this. For example, when welding over a section of oil, the resistance fluctuates and the power supply receives inconsistent information. This causes the power supply to change its parameters to compensate during and after the oily sections.
Fig. 2: A difficult surface to weld
During this change period, the parameters may not be optimal and result in wire stubbing or weld pool agitation, resulting in spatter generation. This is usually seen as a popping of the welding arc as it welds these sections as it tries to compensate. One advantage to our D-series welding power supplies is that they are much faster (compared with conventional models) and can reduce the time required to make adjustments, almost to the point where the welder may not even notice the changes.
The second and more prevalent factor is that the contamination mixes with the weld pool itself. For example, a rusty surface (which contains oxides) will add oxygen to the weld pool, thereby reducing the effects of the shielding gas. The oxygen mixes with the weld pool to form pockets or bubbles of material with slightly different compositions than the weld pool. The result are small amounts of bubbles in the weld pool (known as porosity) which will pop within the weld pool and generate spatter.
Removing the surface contamination is usually very simple. The welder can either physically remove this with a grinder or wire brushes, or apply chemical solvents such as acetone. However, this results in additional steps to the welding preparation process and may not be cost effective.
A better suggestion is to prevent contamination before it starts by protecting the material from weather or damp conditions. In the case of aluminum materials, weld the material as soon as possible when it is processed or received. This will reduce the oxide layer, which grows over time from the instance the aluminum is introduced to the air.
Where to go from here
The best thing for you to next is to stop and evaluate your existing processes: are you currently using these methods discussed above? If not, then now would be a great time to develop your own implementation into your existing welding programs. Experiment with the techniques listed above by trying different combinations, and carefully examine the results you get back.
Also, be sure to check out the continuing part 2 of this article, now available in Tech Tips!
