Welding spatter is not only visually unappealing, but it also impacts the efficiency of a welding operation. In most cases, the spatter must be removed to pass a company’s quality checks. Companies also have to factor in the cost for purchasing grinding equipment and abrasives to remove the spatter, as well as maintenance and the associated safety risks of using grinders.

Anti-spatter compound can prevent spatter from accumulating on a part; however, it should be a last resort. Anti-spatter compound adds to an operation’s expenses and has the potential to introduce weld defects like porosity. It is also notoriously messy and can adhere to equipment, tools and the floor, which poses a slipping hazard.

There are several ways to reduce spatter that result in better-looking welds and greater efficiencies without the use of an anti-spatter compound.

No. 1: Adjust wire and welding parameters.

The diameter of wire used, along with the power source settings —particularly voltage — impact spatter generation.

For example, larger diameter wires operating at lower or colder welding parameters (less voltage), are prone to creating higher levels of spatter. In this situation, the combination of wire type and size, along with certain corresponding welding parameters, will operate in a short circuit transfer. In this mode, the welding wire makes electrical contact as it touches the base material repeatedly per second. Or the combination may move toward a globular transfer mode, causing large droplets of weld metal (larger than the wire diameter) to transfer across the arc. Both can cause spatter.

When welding with less than ideal settings with a larger wire, it may be beneficial to go down to a smaller size — for instance, from an 1.2mm to an 1.0mm wire. A smaller wire with more optimal settings allows for spray transfer mode that sprays tiny droplets of weld metal across the arc. The result is a smoother arc that reduces spatter.

Shielding gas selection also factors into the ability to achieve a smooth spray transfer mode. When welding with solid wires, it’s necessary to use a minimum of 80% argon in the shielding gas mixture. Tubular wires, like metal-cored wire, require a minimum of 75% argon with a CO2 balance. There is a tradeoff with higher argon levels; they produce deep, narrow joint penetration that may be less forgiving than a wider joint penetration. Welding operations will need to determine if that is more of an issue and a cost factor than dealing with
spatter.

No. 2: Avoid mill scale when possible.

The presence of mill scale or scale is a common problem in welding operations. This flaky surface found on hot rolled steel is made up of mixed iron oxides and melts off at a higher temperature than the actual base metal, essentially blocking electrical current to the arc during welding. The result is a colder weld deposit that tends to „ball up,“ as opposed to wetting out smoothly, and it causes welding spatter.

When possible, weld on base material that is free of scale. This can be achieved by purchasing plate that has already been cleaned or by grinding the mill scale off with a grinder or flap disc. Both add cost to the welding operation but can help avoid downtime for spatter removal.

If welding on scale-free material isn’t possible, be sure to ground the power source securely on a clean surface. Grounding over scale can cause interruptions to arc starting that leads to spatter. Using certain filler metals, like metal-cored wire, can also help minimize issues with mill scale and spatter.

No. 3: Consider metal-cored wires.

When possible and appropriate for the welding application, converting from solid wire to metal-cored wire is a good way to control spatter levels. As opposed to a solid wire that has a solid cross section, metal-cored wires are tubular and filled with metallic powders, alloys and arc stabilizers. These wires carry the current through the outside metal sheath, which creates a broader, cone-shaped arc for a wider penetration profile with little to no spatter.

Metal-cored wires also operate in the spray-transfer mode described earlier and can weld well through mill scale without pre-cleaning. Again, the combination reduces the opportunity for spatter.

No. 4: Follow proper welder training and best practices.

Less skilled welders can often produce welds with more spatter. As with any part of the welding operation, welder training and following some best practices are key.

Using the appropriate work and travel angles based on the application, wire type and joint configuration, as well as maintaining a proper contact-tip can also reduce spatter and should be instilled into training programs for new welders.

Also, using the proper consumables and replacing them when needed can help reduce spatter.

Taking steps to reduce welding spatter can help companies streamline their welding processes and be more efficient.

No. 5: Use pulsed MIG welding.

If a welding operation has a power source capable of pulsed MIG welding or is in a position to purchase one, the waveforms it provides can help reduce spatter. Pulsed MIG welding operates by switching between a high peak and low background current approximately 30 to 400 times per second. As the switch occurs, a droplet of wire is pinched off during the peak current and propelled to the weld pool. The background arc is responsible for maintaining the arc during this process, but at a low heat input that prevents metal transfer from occurring.

Pulsed MIG welding pairs well with solid wire and metal-cored wire to reduce spatter and helps with out-of-position welding. Because metal-cored wire already produces little to no spatter, the benefit of spatter reduction is more noticeable when using pulsed MIG welding with solid wire.

Pulsed MIG welding is also relatively easy for new welders to learn, which is an added benefit to creating consistent welds with low spatter, and the process can often weld through mill scale.

Supporting productivity, quality and cost savings.

Taking steps to reduce welding spatter can help companies streamline their welding processes and be more efficient. This is particularly true for applications that require parts to be painted. By lowering or eliminating spatter, the part can be moved more quickly into that portion of the welding operation. Spatter reduction can also support weld quality, increase throughput and minimize unnecessary costs.

Article based on ITW Welding global experience and knowledge.

When it comes to choosing filler metals for critical applications, it’s essential to find ones with the right mechanical and chemical properties. Having the right properties can help provide the proper impact toughness for the application, which is especially important when welding high-strength, low alloy materials. It is also important for applications subject to:

– rapid loading

– cyclic loading

– low service temperatures

– seismic activity

So, what is impact toughness and why is it important?

Impact toughness defined

By definition, impact toughness is the ability of a weld to permanently deform and absorb energy before fracturing, after applying rapid stress to it. Simply stated, it’s how much rapid impact energy a weld can take before it cracks. The application of the stress is typically under one second. In the real world, impacts can result from any number of events, such as:

– high winds

– earthquakes

– intentional and unintentional collisions

– explosions

The value of proper impact toughness

Filler metals with proper impact toughness provide several benefits in critical applications found in structural steel, oil and gas industries, shipbuilding and more. These include:

1. Reducing the risk of brittle fractures in steel that are associated with the combination of impact and cyclic loading and loss of toughness at low service temperatures
2. Helping to arrest the propagation of a crack so emergency repairs can be made

Ideally, however, using a filler metal with good impact toughness and following proper welding procedures will help prevent cracking altogether.

Selecting a filler metal

Filler metal manufacturers follow strict standards for formulating their products, including those set forth by the European Committee for Standardization or American Welding Society (AWS) „A5“ filler metal specifications. These specifications provide testing criteria for the filler metal, along with minimum impact toughness requirements for each filler metal classification. For general purpose applications, select a filler metal that provides minimum impact toughness properties that meet or are better than the impact toughness requirements of the application.

Article based on ITW Welding global experience and knowledge.

Metal-cored wire can bring key benefits to your welding operation compared to using solid wire — namely, improved productivity, higher weld quality, and lower costs.

1. With the same welding wire size at the same operating parameters (amperage), metal-cored wire typically has a higher deposition rate, resulting in faster travel speeds for the same size weld.
2. Metal-cored wire welds have higher tolerance for mill scale, oil, and dirt on the base material, often meaning that cleaning operations can be avoided. This helps manufacturers reduce labor costs and optimize productivity.
3. The wire produces minimal spatter, so there is no need to apply anti-spatter and you can reduce post-weld grinding and cleanup.
4. By eliminating pre- and post-weld activities, you can reallocate labor to other areas of your welding operation where welders can help increase throughput.
5. Metal-cored wire provides good gap bridging and weld fusion to reduce the need for rework.
6. Metal-cored wire is easy to use, so it can simplify training for new welders. The welding technique is very similar to solid wires.

Overall, metal-cored wire produces high weld quality and can yield up to a 30 percent increase in productivity. Faster cycle times mean you can get more parts out the door and gain a better bottom line.

In the right welding operation, metal-cored wire can provide process improvements and simplify training, particularly if you have less-skilled welders.

Metal-cored welding wire is a composite tubular wire that consists of a metal sheath with a core of metallic powders and alloys. In many situations, this wire can increase your welding efficiencies and reduce overall costs compared to solid wires.

When should metal-cored wire be used?

Metal-cored wire is especially effective when used in heavy equipment, automotive, and general manufacturing applications, and is a good alternative to solid wire when welding 3- to 6-mm thick mild steel.

It can also help if you are experiencing challenges in your welding operation, such as:

1. Poor fit-up, gaps or burn-through issues
2. Inadequate side wall fusion
3. High levels of scrap or rework
4. Excessive time and money for pre- and post-weld cleaning
5. Slow new welder training

To decide if metal-cored wire is right for you, it’s important to understand how the technology works and the key benefits it can provide.

Cost is always a factor when making a decision about your welding operation. Fortunately, the cost to change from solid wire to metal-cored wire is generally minimal — especially if you factor in the labor savings and increased productivity you can gain.

There are a four key steps to the process.

1. Welding operation study.  Your filler metal provider can study your operation on-site or recreate the part production in its lab using solid wire and metal-cored wire — comparing the difference in travel speed, deposition rates and the time to complete the part.  From there, the provider can prorate the welding cost savings using metal-cored wire on per-shift, monthly or yearly basis.
2. In-house trial. After reviewing the metal-cored wire data, you can trial the wire in a single welding cell, working with a filler metal specialist to optimize the parameters. Trials may run for a day, week, or even a month based on your preference.
3. Potential welding procedure requalification. You may need to requalify your welding procedure for use with metal-cored wires, and it may be possible to conduct the testing in-house. If you require additional mechanical property testing, you can work with a third-party testing lab to ensure that your choice of metal-cored wire is qualified to your application.
4. Conversion. Metal-cored wire can be implemented by changing over one cell or a group of cells at a time or during routine weld cell maintenance.

As with any change in the welding process, converting to metal-cored wire takes careful consideration. Consult with a trusted filler metal manufacturer or distributor to help with the process.

MIG Troubleshooting for Metal-Cored and Solid Wire

MIG welding (also known as GMAW) is a popular process because of the productivity, reliability and ease of use it offers. However, issues can arise if a welder doesn’t use proper technique and parameters or perform proper equipment setup and maintenance. To help reduce lost productivity and downtime costs, it’s important to know how to quickly identify and solve issues like porosity, undercut, excessive spatter and more. Here are tips to identify and correct problems associated with using both metal-cored wire and solid wire in the MIG welding process.

Issue 1: Porosity

The most common cause of porosity when MIG welding is poor shielding of the weld pool, leading to contamination by atmospheric gases. Poor shielding occurs when the shielding gas flow is restricted, turbulent or insufficient.

Environmental factors such as wind can displace gas flow. It is best to relocate to an area with less wind, but screens can be used if they can reduce wind velocity in the welding area to 8 kilometers per hour (kph) at most.

Spatter buildup in the nozzle can also cause a turbulent or restricted flow. Be sure to periodically check the nozzle for excessive spatter buildup; if present, remove this buildup with welder’s pliers. While the nozzle is removed for cleaning, ensure that the diffuser’s gas ports are unobstructed.

An insufficient flow typically results from setting the shielding gas flow meter incorrectly or using too small of a welding nozzle diameter for the weld pool being created. A flow rate of 15 to 22 l/min is often recommended when welding using a spray transfer. Welds that use higher amperages may require a higher flow rate. Be aware that excessive flow rates (especially relative to the nozzle diameter being used) and nozzle obstructions can lead to turbulence, which can introduce atmospheric gases into the shielding gas column.

Base metal contamination with oil, grease, mill
scale, rust or moisture can lead to welding porosity.
While metal-cored wire better tolerates base metal
contamination than solid wire does, it’s still important
to properly clean the material before welding.

When using solid wire with a short-circuit transfer process, welders can use lower flow rates — approximately 12 to 15 l/min — and still adequately shield the weld. The lower voltages and amperages of the short circuit transfer produce smaller weld pools that require less shielding gas to protect them from the atmosphere.

Base metal contamination with oil, grease, mill scale, rust and/or moisture can also lead to welding porosity. While metal-cored wire often better tolerates base metal contamination than solid wire does, it’s still important to properly clean the material of excessive contaminants before welding. Remember to store welding wires in a clean, dry place with a temperature similar to the welding environment; doing so minimizes the risk of condensation that can contaminate the material.

Issue 2: Undercut

Undercut can be created when the welder focuses the arc too much on the bottom plate and not enough on the top plate of the weld joint — in other words, when the welder uses an incorrect gun angle. Other common causes are excessive voltage and travel speeds that are too fast without using enough filler metal. If undercut is happening toward the end of the joints, arc blow (or arc wander) may be the cause.

Voltage influences arc force. When voltage is too high, it can cause the arc to want to push the molten weld pool out of the way. It also results in a more fluid pool with less surface tension that helps fight the pull of gravity to maintain an appropriate bead shape. Reducing the travel speed and increasing wire feed speed to ensure there is sufficient wire to fill the joint and areas gouged by the arc can help combat undercut. Pausing longer at each side of the weld bead when using a weave technique can also help.

To reduce the effects of arc blow, try moving the work lead clamp (often called the ground) to a different spot.

Issue 3: Weld spatter

A short-circuit transfer will always create higher spatter levels than a spray transfer. To generate minimal spatter levels and achieve maximum travel speeds, use sufficiently high voltages and wire feed speeds to obtain a spray transfer whenever possible. A voltage that is too low in relation to the wire feed speed is the most common contributor to excessive spatter levels, regardless of the transfer being used. Ideally, voltage should be high enough to minimize spatter, but not so high as to cause undercut.

The MIG welding process — whether it uses solid wire
or metal-cored wire — can be prone to common pitfalls.
To help reduce the downtime and costs associated with
troubleshooting, it’s important to know how to quickly
identify and solve issues.

MIG welding can tolerate some degree of base metal contaminants (particularly when using metal-cored wire) but the presence of base metal rust or mill scale increases the amount of spatter generated in addition to increasing the risk of porosity. Minimizing spatter is a matter of balancing the acceptable level against the time spent cleaning the base metal.

Spatter levels can also be influenced by shielding gas and wire selection. A 75% argon/25% carbon dioxide gas mixture typically results in less consistent transfer that generates more spatter than a 90% argon/10% carbon dioxide mixture. All other things being equal, metal-cored wire generally has a smoother arc that produces less spatter than solid wire.

An uncontrollable, erratic arc that generates high amounts of spatter repeatedly in one area of the weld/part is a typical symptom of arc blow. It can often be corrected by moving the work clamp or changing travel direction with respect to the work lead clamp.

Issue 4: Lack of fusion and poor penetration

Metal-cored wire typically provides a wider penetration profile than solid wire, making it easier to achieve fusion into the side walls of the weld and avoid lack of fusion in these areas. However, issues can still arise if the welding procedure and technique used are not optimized.

Welding current that is too low is the most common cause of lack of fusion. The amperages required to run a spray transfer mode with MIG welding typically help prevent lack of fusion. Stay out of the globular and short-circuit transfer ranges, which do not offer significant penetration.

„Riding the pool“ may be a cause, too. This happens when travel speed is too low for the wire feed speed and voltage selected so that the weld pool forms and/or flows significantly ahead of the wire. To prevent the issue, stay on the leading edge of the weld pool to maximize penetration and sidewall fusion. To stay on the leading edge without changing travel speed, reduce the wire feed speed. Conversely, to stay on the leading edge without changing the wire feed speed, increase the travel speed.

Running too small of a wire diameter can be another cause of fusion or penetration issues. Smaller wire diameters typically form narrower arc cones that may be too narrow and unable to spread out the molten filler metal. Larger diameter wires have lower deposition rates for the same amperage compared to smaller diameter wires, but offer a wider arc cone that assists fusion into the sidewalls. Larger diameter wires also allow welders to weld at higher currents with good arc stability; this is helpful if the current can no longer be increased while maintaining good weld quality when using a smaller diameter wire.

Welder technique and travel angle can also affect weld fusion. With solid and metal-cored wires, a push angle is typically used, but an excessive push angle can reduce penetration. Poor penetration in MIG welding can also be caused by joint design. It can help to open up the bevel angles of the joint or use a wider root opening.

Remember to store welding wires in a clean, dry place
with a temperature similar to the welding environment;
doing so minimizes the risk of condensation that can
contaminate the material.

Issue 5: Overlapping (cold lap)

Overlapping, also called cold lap, happens when the filler metal doesn’t fuse into the base material at the weld toes.

As with many other welding defects, this problem is often the result of multiple simultaneous factors. Overlap may be caused by riding the weld pool while adding too much filler and having insufficient voltage to spread the weld pool to the appropriate width. This problem can be remedied by increasing voltage and travel speed and reducing wire feed speed. Remember, it’s important to always stay on the leading edge of the weld pool for optimum weld penetration and quality.

Proper angle can also help eliminate cold lap. Welders should be sure to distribute the arc cone equally between the two base plates of a weld joint, assuming there is equal material thickness. One benefit of metal-cored wire is that the wider arc cone helps spread the weld metal out, so it’s more forgiving to variations in work angle than solid wire, which can help minimize the risk of cold lap.

Issue 6: Weld cracking

Both metal-cored and solid wires generally have low hydrogen levels and are resistant to moisture pickup that can contribute to hydrogen-induced weld cracking. However, cracked welds can be caused by numerous other factors, too. These include insufficient weld size, excessive joint restraint, poor joint design or a rapid weld cooling rate. Cracked welds can also result when the filler metal chemical composition is incompatible with the base material or the tensile strength and ductility of the filler metal doesn’t match the base metal or the application demands.

Adjustments can be made to weld procedures to obtain higher weld ductility and help prevent cracking. Shielding gas selection, for example, impacts ductility. Shielding gases with higher argon content (example: 90% argon/10% carbon dioxide) tend to offer smoother arc characteristics than lower argon shielding gas mixtures. They also tend to increase tensile strength, which can reduce weld metal ductility.

Addressing common MIG welding issues — whether porosity,
spatter or lack of fusion — can often be done with some
simple changes to joint design, welding technique or parameter
settings.

It is important to adjust the weld size to match the part thickness, reduce the weld cooling rate through the use of preheat, and reduce joint restraint through proper design. Very narrow, deep joints on thicker materials increase crack sensitivity, whether using solid wire or metal-cored wire.

Issue 7: Distortion

Welding distortion can be caused by many factors, but one likely culprit is part design or faulty joint preparation that requires additional weld volume. Making changes to design can help reduce distortion. For instance, instead of tack welding a 90-degree T joint, tack weld the parts slightly off square. This incorporates distortion during welding into the as-designed dimensions. Fitting the part to compensate for the distortion is often called presetting the joint. Intentionally bending parts before welding to compensate for distortion is often called precambering the joint.

Heat input is reduced when amperage and voltage are decreased and/or travel speed is increased. Minimizing heat input can help limit distortion. Metal-cored wire offers advantages over solid wire because it can provide a lower heat input (due to lower amperage) for the same wire feed speed.

MIG welding troubleshooting

Addressing common MIG welding issues — whether porosity, undercut, spatter or lack of fusion — can often be done with some simple changes to joint design, welding technique or parameter settings.

In addition, using metal-cored wire rather than solid wire in the right applications can deliver numerous benefits that help address some of these basic MIG welding problems. In either case, knowing how to quickly identify and solve problems can help keep the welding operation on track — in terms of quality, productivity and costs.