Follow These Tips for Stronger, Safer Shop Welds

Having the right kind of welder in your farm shop can save time and money on repairs and fabrication. MIG welders have become common on the farm, but there’s still a place for stick welders – and TIG welders are also appearing for certain jobs. While this article focuses on MIG welding and general techniques and safety precautions, find tips for other types of welding at Agriculture.com/welding. 

MIG Welding

MIG (metal inert gas) welding, also known as FCAW (flux-cored arc welding), is the popular choice for many farmers because of its ability to produce clean welds on a variety of materials. 

6 Tips for Better MIG Welding Results

1. Clean. Then Clean Again.

The No. 1 failure of a MIG weld is porosity, and the most common cause of porosity is welding a dirty, oily, or painted surface. Contaminants become trapped in the weld, resulting in sponge-like holes. Other causes include inadequate shielding gas coverage or improper wire stickout. 

“Farmers commonly fail to adequately prepare metal before welding,” says John Leisner, service training manager for Miller Electric. “This includes removing paint, rust, dirt, and other surface contaminants, and it also means grinding out cracks.”

Hydrogen is the worst weld-destroying impurity and is a particular challenge for welders because it’s found everywhere (think water, dirt, rust, paint, manure, grease). Careful cleaning can help mitigate hydrogen’s presence in your weld, giving you a stronger and more attractive finished project.

2. Get Grounded.

A welding arc requires a smooth flow of electricity through a circuit, and while electrical current flows through any available path, the majority will seek the path of least resistance. If your ground is not placed near the arc, the current may find another path, resulting in poor welder performance. Firmly attach the clamp to bare metal as near as possible to the arc. 

If you’ve ever fired up your MIG welder and heard popping or crackling sounds, this could be due to a poor ground clamp, according to Jody Collier, welding educator at weldingtipsandtricks.com. Copper ground clamps are best, especially ones with strong springs. A good clamp makes for a good ground.

3. This Is a Stickout!

Wire stickout is sometimes misunderstood. According to the American Welding Society (AWS), it refers to the distance from the end of the nozzle to where the wire melts off. As a general rule, the wire should stick out from the end of the gun’s contact tip between ¼ and 3⁄8 inch. Too much stickout softens the arc, making the weld pile up; however, in certain situations, such as welding thin sheet metal, a longer stickout is useful.

4. Fine-Tune Your Technique.

“Use both hands when possible,” Collier says. “Rest the crook of the gun neck in one hand and hold the part with the trigger in the other hand.” He recommends heat-resistant, heavy welding gloves for protection. 

The most common method is to push the gun toward the direction of the weld, known as the forehand method. Forehand welding produces shallow penetration with a flat, wide, smooth surface. The backhand method – pulling the gun toward you – produces a deep-penetration weld that is narrow and high in the center. The best method to use is determined by the thickness of your metal and how deeply the weld needs to penetrate. 

When making out-of-position welds (vertically, horizontally, or overhead), use the smallest-possible wire diameter size and keep the weld pool small.

Take a look at your finished welding bead. A convex shape or rope-like bead often indicates your setting is too cold for the thickness of the repair and there isn’t enough heat being produced to penetrate the base metal. A concave shape bead can indicate too-high voltage, too-slow wire feed speed, or too-fast travel speed.

5. Evaluate Your Equipment. 

Make sure to match drive rolls, gun cable liners, and contact tips to the wire size you’re using. Trying to run .030-diameter wire through .035 rolls will have you constantly changing feed speed and never getting the setting right, as the grooves on the rolls are too large. The same goes for the gun cable liner and contact tip sizes. 

Clean the gun liner and drive rolls occasionally, and keep the gun nozzle clear of spatter. Replace the contact tip regularly, because worn tips can lead to an erratic arc, Collier says. If a tip enters the molten weld pool, replace it immediately. 

Over time, gun liners can become clogged with dust and copper from the wire. You can check the liner for feeding issues by turning off the machine, undoing the spring clamp tensioner on the rollers, and laying the gun lead on the floor, with the contact tip removed. You should be able to push the wire through without having to force it; if not, replace it. New liners are inexpensive and make a noticeable difference. 

Your welder should produce a steady buzz while welding. Hissing can indicate your voltage setting is too high, says Miller Electric’s Leisner. A loud, raspy sound can indicate the voltage is too low, while a constantly changing pitch or volume can indicate too long of a wire stickout.

6. Take Steps for Safety.

A good auto-darkening helmet can make a huge difference in your final output. Moving even ¼ inch off the welding track when you nod your helmet down can screw things up. With a quality auto-darkening helmet, you can see where your wire is pointing before you pull the trigger. Leather footwear along with flame-resistant clothing without cuffs or open collars are recommended to prevent burns and eliminate places where sparks can hide and smolder. 

If you must use an extension cord, use the shortest length and biggest diameter possible. 

Ensure your welding equipment is on a flat surface away from flammable materials, including paper, cloth, rags, oil, and gasoline. Avoid working in damp or wet conditions. Keep the work area free from clutter and keep necessary tools nearby. Never pick up hot metal with your hands, even when wearing gloves – use pliers. 

Make sure your shop area is well ventilated to protect you from fumes, dust, and particles created during welding. You can use a fan to help pull fumes away from your breathing area.

MIG Gas Selection Tips

For MIG welding, an economic and efficient choice of gas is 100% carbon dioxide (CO2). However, when welding thin metal, CO2 may be too hot. Welding educator Collier suggests a mixture of 75% argon and 25% CO2 instead. 

There are other shielding gas mixtures, and for certain uses it may make sense to invest in something more expensive.

• Use 75% argon and 25% CO2 for nice-looking welds (100% CO2 produces a lot of spatter) and for welding at high amperages. 
• Use 85% argon and 15% CO2 for welding heavier-plate steel or for using on metal with considerable mill scale or rust.
• Use 90% argon and 10% CO2 for spray transfer welding and for heavy or thick sections of metal. 
• Use 100% argon or an argon/helium mixture for welding aluminum.
• Use 98% argon and 2% CO2 for stainless steel. 

For most farm shop needs, on-hand gas supplies should include CO2 and an argon-CO2 mixture.

MIG Wire Selection Tips

Although the most common welding wire diameters are .035 and .045 inch, a smaller-diameter wire can make it easier to create a good weld. Try an .025-inch wire diameter when welding material of 3⁄16 inch or less. A smaller-diameter wire produces more stable welds at a lower current, which has less tendency to burn through. 

While a lower current and smaller wire can mean greater success on thinner materials, be careful using that approach on materials 3⁄16 inch or thicker because a .025-inch wire may cause lack of fusion.

Aluminum Welding Tips

More ag equipment is incorporating aluminum, forcing the issue of needing to make repairs to the metal. Any wire welder can handle aluminum, and the process is fairly easy to learn, according to Lincoln Electric. Keep in mind a few things:

• Buy U-groove drive rolls that support the wire without crushing it. Keep drive-roll adjustment on the loose side.
• Replace the cable lining using a Teflon, nylon, or similar liner product. 
• Use only argon or argon-helium gas. 
• Select an aluminum filler wire that is 3/64 inch or 1/16 inch in diameter. These larger wires are easier to feed down the gun cable. 
• Employ a contact tip approximately .0015 inch larger than the diameter of the wire.
• Remove grease, oil, manure, and dirt by using an organic solvent such as acetone, a mild alkaline solution such as strong soap, or a citrus-based degreaser. Avoid strong alkaline or acid cleaners. 
• Brush the repair using a new stainless-steel wire brush (only used for aluminum welding jobs) to remove the oxidized aluminum that occurs naturally on the surface of the metal. Aluminum oxides melt at 3,700°F, while the base metal melts at 1,200°F. Oxides on the repair surface inhibit penetration of the filler metal. 
• Preheat the repair to no higher than 230°F to minimize cracking. Place tack welds at the beginning and end of the repair to aid in preheating and to prevent distortion. 
• Use a short gun and a straight cable. If you are doing a lot of aluminum welding, consider buying a spool gun. 
• Push into the weld to reduce contamination and to improve shield gas coverage. 
• Weld hot and fast using higher amperage and voltage settings and faster weld-travel speeds to prevent burn-through. 
• Fill the weld crater at the end of a weld. Craters are the leading reason aluminum welds crack. To fill the crater, continue to feed wire at the end of a weld, reversing your direction of travel back over the weld for about 1 inch. 
• If you aren’t welding the repair site immediately after cleaning, cover the welding joint with brown kraft paper to prevent dirt and grit from the air from settling into the weld area.