Glob or spray modes for thick steel

Most farmers may not realize that adjusting the volts, amps, and wire speed on wire welders can produce transfer modes fine-tuned to thick metal. The limiting factor with globular or spray modes is they can only be used on “metal ⅛-inch thick and thicker and only when making flat and horizontal fillet welds,” says Lincoln Electric's Karl Hoes.

Globular transfer (short arc): Voltage, amperage, and feed speed are higher than the standard short circuit mode. This results in large globs of wire expelling off the end of the wire to enter the weld puddle. This mode provides deep penetrating welds on thick material, but it produces a lot of spatter.

Spray arc transfer: The volts, amps, and wire speed are higher than in globular mode. It produces a stream of tiny molten droplets that spray across the arc from wire to metal. For true spray transfer, you'll need to use argon-rich gas. Spray arc allows the use of large-diameter wire, so a lot of metal is deposited, and you get a great-looking bead. It can only be used on flat or horizontal fillet welds; its puddle is very fluid. Be sure to change your gun's nozzle to a unit that is about 3 inches long or longer. 

Clean out impurities

“Farmers commonly fail to adequately prepare the metal before welding,” says Miller Electric's John Leisner. “This includes removing paint, rust, dirt, and other surface contaminants, but it also means grinding out cracks.” Leisner readily understands that metal prep is the last thing on your mind when a weld repair is needed at the height of the season or in the middle of feeding livestock.

“I'm not saying the repair area must be absolutely pristine,” he says, adding that aluminum welds are the exception (see tip number 6 on welding aluminum). “At the very least, hit the repair area with a powered wire brush to remove rust and dirt.”

Cleaning removes the impurities that get absorbed into the metal during weld; if they stay behind, they compromise the repair. If cleaning isn't possible, avoid mending a repair with a MIG welder. “Use a stick welder and a 6011 rod. Also, slow your travel speed down. This allows time for gas bubbles to boil out of the molten weld before these impurities are trapped inside the weld,” he says. 

Hydrogen is welding enemy #1

Hydrogen is the worst weld-destroying impurity around. Because it is everywhere (in water, dirt, rust, paint, manure, grease), hydrogen is a huge challenge for welders. What can be done to gun down hydrogen? Clean, clean, and clean some more. “Hydrogen, along with high-residual stress and crack-sensitive steel, may result in cracking hours or days after welding,” says Lincoln Electric's Hoes. “High-strength steels (commonly used on tillage implements), thick sections of metal, and restrained parts are more susceptible to hydrogen cracking.” 

Rules on angle, direction, and speed

One of the amazing aspects of welding is that even a novice welder can experience some success. However, Hose and Leisner caution that there are some hard-and-fast rules to produce a lasting welding repair.

Push or pull: Here the rule is simple. “If it produces slag, you drag,” says Leisner. In other words, you drag the rod or wire when welding with a stick or flux-core wire welder. Otherwise, you push the wire with metal inert gas (MIG) welding.

Work angle: With wire welding, hold the gun at a 10° to 15° angle into the direction you are pushing the weld. With stick welding, maintain a 20° to 30° lead angle in the dragging direction. With a fillet (tee) weld, hold the rod or wire (regardless of weld process) at a 45° angle between the two pieces of metal.

Arc spacing: Adjust travel speed so that the welding arc stays within the leading one-third of the weld pool. For wire (flux-core or MIG) welding, keep a work distance of ⅜ to ½ inch. With stick welding, look to keep that distance ⅛ inch between the rod tip and workpiece. “The arc length should not exceed the diameter of the core of the electrode,” Leisner says.

Speed: Watch the welding puddles and ridge (where the molten metal solidifies). When wire welding (MIG or flux-core), the ridge should be approximately ⅜ inch behind the wire electrode, Hoes says. A too-slow travel speed produces a wide, convex bead with shallow penetration that also deposits too much metal. On the other hand, a too-high travel speed creates a shallow weld that produces a narrow and highly crowned bead. Most travel speeds for various joints are well below 40 inches a minute.