MATTERS OF SPATTER
Weld spatter used to be an inevitable problem that you just had to deal with ? but with new technological processes being developed, this may not necessarily be the case.
Posted: April 12, 2010
Weld spatter is an all-too-common and persistent issue ? one of those things that you hate, but you figure you just have to deal with. But that's not necessarily true, because there are actually many ways to control it. Weld spatter consists of small balls of molten metal that are created near the welding arc that stick to the gas shroud of the weld gun and block gas flow. Resulting problems include the spatter sticking to work pieces and/or tooling, injuries to workers, clean-up, porosity and loss of material.
Even when using spatter-preventative methods, it eventually builds up inside and on the weld nozzle and nozzle tip anyway, restricting the inert gas flow and causing porous, brittle weld joints. Fortunately, there are many options for reducing, or even eliminating, this dangerous and costly nuisance.
What causes spatter? Well, according to Matt Brooks of OTC Daihen, Inc. (Tipp City, OH), a manufacturer of welding equipment, cutting equipment, torches, robots, positioning equipment, and standard and custom arc welding cells, there could be several causes. According to Brooks, the main factor is a disturbance in the molten weld pool during the transfer of wire into the weld, typically caused by voltage being too low or amperage being too high, which in turn means the arc is too cold to keep the wire and pool molten and causes a stubbing effect of the wire. Spatter may also occur because of the gas selected for use ? for example, CO2 creates more spatter than MAG welding.
Additionally, coatings are one way to go when looking to reduce weld spatter. For instance, ND Industries® (Clawson, MI), developer of fastening and assembly technologies, came up with a creative solution to help reduce their weld spatter problems. Their need for a spatter solution arose because they felt that cleaning spatter off a welding nozzle took too much time, and that most anti-spatter sprays or dips do not prevent spatter adhesion, must be frequently reapplied in order to be effective, and can be messy and even dangerous. In addition, the company wished to provide an alternative to procedures such as reaming, which they viewed as costly and inefficient, so they came up with Spatter-Nix, which is a new coating application. According to the company, this coating process helps prevent weld spatter accumulation, improves MIG gas flow and weld quality, reduces the frequency of nozzle cleaning, makes nozzle cleaning faster and easier, increases the lifespan of MIG weld nozzles and reduces the need for anti-spatter dips and sprays.
Ideal for thin metal automotive applications (0.7-1.0 mm) that employ a longer electrode, Spatter-Nix is a slick coating process that allows the spatter to be vibrated out. It coats the weld nozzle inside and out, providing maximum protection against spatter. (Internal coating length is dependent on the presence or absence of an insulator.) Even if the coating chips or flakes off outside of nozzle, the coating performance inside the nozzle and on the weld tip remains unaffected.
According to ND, the process has been garnering great response from welding companies. FIC America Corporation, a manufacturer of "stitched" welded muffler parts for Toyota, experienced improved productivity. Weld nozzle cleaning was reduced from every 15 minutes to every six hours, and weld nozzle cleaning was reduced from once every five cycles to once every 500 cycles. At one major automotive plant, Spatter-Nix was applied to two weld nozzles of robotic welders. Each robot performed six welds on each piece welded, averaging of 25 to 35 pieces welded per hour. The robots were employed continuously for two eight-to nine-hour shifts per day. Normally, operators found it necessary to clean the weld nozzles an average of three times during every eight- to nine-hour shift, but with this coating application, the robotic welders ran for six consecutive shifts without the need for cleaning.
In addition, a Tier 1 automotive supplier used Spatter-Nix on a robotic welder that performed seven-inch welds. The weld nozzle typically required reaming every four weld cycles. With the use of Spatter-Nix the robotic welder was able to complete 184 welding cycles without the need to ream the weld nozzle. What little spatter that did build up inside the nozzle was able to be removed with a gentle tap to the nozzle. Weld nozzle cleaning reduced from every six minutes to once every 100 hours. Also, a tool and die welding company implemented Spatter-Nix coated nozzles used in a heavy die repair application. In one application multiple welds were performed on steel pieces about five feet long and 3/4 in thick. The welding of one piece took, on average, 45 minutes to one hour. The hand welder found it necessary to clean his weld nozzle at least 10 times during the welding of one piece. Using a coated nozzle, the welder was able to weld 10 pieces without cleaning the nozzle.
As stated earlier, the type of gas used in welding may also contribute to spatter. According to Lincoln Electric (Cleveland, OH), Argon can be very useful in this area. According to the company, for most mild steel applications, CO2 will provide adequate shielding, but when you must have a flatter bead profile, less spatter or better wetting action, you may want to consider adding 75- to 90-percent argon to your CO2 shielding gas mix. Argon is inert to the molten weld metal and therefore will not react with the molten weld metal. When CO2 is mixed with Argon, the reactivity of the gas is reduced and the arc becomes more stable. However, Argon is more expensive. In production welding, selecting the perfect shielding gas can be a science of its own. Attributes such as material thickness, welding position, electrode diameter, surface condition, welding procedures and others can affect results. But fortunately, whether you decide to use a coating, try different gases, adjust your voltage, or try another solution, combating weld spatter is getting easier.
FIVE WAYS TO PREVENT WELD SPATTER:
(From robots4welding.com)
1. Up the Voltage. Cut down on spatter by adjusting your voltage. Voltage is closely tied to the welding arc's length and the heat input of the weld. Find the right balance, so the weld is being created with the right intensity.
2. Up the Voltage. Make Sure the Welding Surface is Clean. One simple way to avoid spatter is to keep your welding surface free from contamination. Substances like oil may trigger the welding power supply to alter parameter settings – creating spatter before and after the right adjustments are made. Anything that oxidizes the weld pool (such as rust) may cause bubbles – which burst, creating more spatter. It's best to clean the surface and avoid the mess. Remove buildup with an abrasive tool or chemical.
3. Up the Voltage. Secure the Welding Environment. In the fight against spatter, wind is an enemy. Make sure your shielding gas isn't being affected by air circulation. Another environmental problem that causes spatter, cable grounding, can be easily fixed. Make sure cabling is secure and on clean surfaces.
4. Up the Voltage. Find the Right Torch Angle. Angling your torch with the wire in front may make a nice, smooth weld, but it shoots spatter outward. A drag angle with the wire behind keeps spatter in the weld pool.
5. Up the Voltage. Pay Attention to the Shielding Gas and Wire. Make sure your shielding gas and wire are preventing spatter, not contributing to it. Argon gas can minimize spatter, but it can change other aspects of the weldment. Many wires have deoxidizing substances in them, which will decrease the amount of spatter. Flux cored wires are a good safeguard against spatter.
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