Frequently Asked MIG Welding Questions

By Randy Glassburn, Marketing, Lincoln Electric Company

Here are some of the most frequently asked questions that The Lincoln Electric Company receives regarding general MIG welding issues.

• Does my choice of MIG welding wire really affect the quality of the weld?
• Does shielding gas affect the quality of the finished weld?
• Are there any other tips you can provide for higher-quality MIG welding?
• How important is a good electrical ground in MIG welding?
• How important is the contact tip in MIG welding?

Q: Does my choice of MIG welding wire really affect the quality of the weld?

A:Yes. While there are many options on the market today for mild steel welding wire, we will concentrate on the two most popular for small shops or hobbyists.

Lincoln Electric offers several types of its copper-coated SuperArc® MIG wire, including the popular L-50 and L-56. Although both are 70,000-lb. tensile-strength wires designed for welding mild or carbon steels, it is the amount of “deoxidizers” found in the wires that sets them apart.

SuperArc L-50 (AWS classification ER70S-3) is a great general fabrication MIG wire and it usually allows you to make quality welds on clean steel. For production work, .035” and .045” are the most common diameters.

However, you may want consider SuperArc L-56 when you need to weld steels that have less-than-perfect surface conditions. In the same way you can upgrade gasoline for your automobile from regular to premium for enhanced performance, you can do the same for welding wire.

For this reason, SuperArc L-56 wire (AWS classification of ER70S-6) carries more deoxidizers in its chemistry. This means that it has more built-in “cleaning action” to handle contaminants of welding such as surface rust, oil, paint and dirt. With L-56, you may not be required to do as much cleaning of the steel before welding. This higher quality of cleaning offered by the deoxidizers usually translates into a higher-quality weld materials with less-than-stellar surface conditions. Most automotive manufacturers now mandate this type of wire for any automotive repairs. In addition, this wire is available in diameters ranging from .025” to 1/16” which meet the welding performance demands of thin sheet metal (24 gaige) to heavy plate welding.

Q: Does shielding gas affect the quality of the finished weld?

A: Yes. 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% argon to your CO₂ shielding gas mix.

Why? Argon is essentially 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. But, 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.

Common gas mixes for the home hobbyist and small fabricator would be:

• 100% CO₂ — Lowest price, generally greatest penetration, and higher levels of spatter. Limited to short circuit and globular transfer.
• 75% Argon - 25% CO₂ — Higher price, most commonly used by home hobbyist and light fabricator, lower levels of spatter and flatter weld bead than 100% CO₂. Limited to short circuit and globular transfer.
• 85% Argon - 15% CO₂ — Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and excellent penetration for heavier plate applications and with steels that have more mill scale. Can be used in short circuit, globular, pulse and spray transfer.
• 90% Argon - 10% CO₂ — Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and good penetration for a wide variety of steel plate applications. Can be used in short circuit, globular, pulse and spray transfer.

Try C-25 Shielding Gas (75% Argon, 25% CO₂ )

Q: Are there any other tips you can provide for higher-quality MIG welding?

A: Try a smaller-diameter wire. Although the most common diameters of welding wire are .035” and .045”, a smaller-diameter wire usually will make it easier to create a good weld. Try an .025” wire diameter, which is especially useful on thin materials of 1/8” or less. The reason? Most welders tend to make a weld that is too big, leading to potential burn-through problems. A smaller-diameter wire produces more stable welds at a lower current, which gives less arc force and less tendency to burn through. If you keep your weld current lower, you will have a greater chance of success on thinner materials. This is a good recommendation for thinner materials, but be careful using this approach on thicker materials (>3/16”) because there may be a risk of lack of fusion. Whenever a change like this is made, always verify that the quality of the weld meets its intended application.

Try SuperArc .025" L-56!

Q: How important is a good electrical ground in MIG welding?

A: In arc welding, an arc is established from the electrode to the workpiece. To do this properly, the arc requires a smooth flow of electricity through the complete electrical circuit, with minimum resistance. If you crimp a garden hose while watering the lawn, the flow at the sprinkler head is much reduced. Beginning welders often make the mistake of attaching the work clamp (or electrical ground) to a painted panel or a rusty surface. Both of these surfaces are electrical insulators and do not allow the welding current to flow properly. The resulting welding arc will be difficult to establish and not very stable. Other telltale signs of an improper electrical connection are a work clamp that is hot to the touch or cables that generate heat. Another key point to consider when attaching the welding ground is to place the welding ground on the piece being welded. A welding current will seek the path of least resistance, so if care is not taken to place the welding ground close to the arc, the welding current may find a path unknown to the operator and destroy components unintended to be in the welding circuit.

SO, FIRMLY ATTACH WORK CABLES TO CLEAN BARE METAL AND CLOSE TO THE WELDING ARC.

Q: How important is the contact tip in MIG welding?

A: Very important. Make sure the gun tip isn’t worn out or that weld spatter is not on the tip near the exit hole. The contact tip in the gun should be perfectly round and just a few thousandths larger than the wire itself. Worn tips are typically oval and can cause an erratic arc because of the random electrical connection and physical movement of the wire inside the worn tip. Genuine Lincoln® contact tips are precisely made from a wear-resistant copper alloy for superior welding performance. If the contact tip enters the molten weld pool, it should be immediately replaced. For most casual welders, a good rule of thumb to assure high-quality welding is to change the tip after every 100 lbs. of wire. Another point to remember about contact tips is that they should always be threaded completely into the gas diffuser and tightened prior to welding, to give a smooth flow of welding current.

IF THE CONTACT TIP LOOKS QUESTIONABLE, GET A NEW LINCOLN TIP, THREAD IT COMPLETELY INTO THE GAS DIFFUSER AND TIGHTEN.

Conclusion:

The Lincoln Electric Company offers a full range of MIG solutions. Take a look at our equipment like the mid-sized PowerMIG® 255, the Waveform Control TechnologyTM tour de force named the PowerWave 455, and rugged, adaptive Series 10 wire feeders capable of MIG pulsing. Even more importantly, try for yourself the consistent quality and feedability of Lincoln's SuperArc® copper-coated and SuperGlide® bare mild steel wires, the carefully crafted Blue MaxTM Stainless MIG wires, and the wide range of aluminum SuperGlaze® MIG wires now available.