MIG welding aluminum

Mar 31, 2003 12:00 PM, David Anderson

From everyday maintenance to construction on the farm, your wire welder has that go-anywhere, weld-almost-anything flexibility that makes it one of your favorite pieces of equipment. And although mild steel is a more common metal on a farm, the presence of aluminum, which is considered somewhat more difficult to weld, is growing. Stock trailers and irrigation systems are examples of standard farm equipment made from aluminum parts.

Over the years metal inert gas (MIG) arc welding of aluminum has become increasingly popular due to the advancement of welding technology. Because certain properties of aluminum are different from those of steels, some welding techniques and parameters are different.

Here are some tips for successfully welding aluminum with your all-in-one MIG wire welder:

• Set the power source for reverse polarity (DCEP).
• 100% argon shielding gas is generally used for MIG welding aluminum.
• Use a wire diameter appropriate for your application. Generally, thicker wire works better for thicker applications and vice versa.
• Use the appropriate wire type. ER4043 and ER5356 are the most common wire types for welding aluminum. However, they have different properties and melts at a different speed, which can affect your desired result.
• When installing the wire spool, check both the spool tension and the drive-roll tension. The spool tension should be less than what would be set for steel wire. Drive-roll tension should provide an even wire-feed rate. Too much or too little drive-roll tension can cause burnback.
• When installing the gun, be sure the liner extends from the outlet guide back into the drive roll and as far into the contact tube adapter as possible. If the liner is cut too short, it can cause the wire to tangle, creating what is called a bird nest.
• Because aluminum forms a hard oxide layer when exposed to air, it is necessary to brush the weld area with a stainless steel wire brush before welding. This will help break up the oxide layer. Remaining oxide will be burned off during the weld process.
• To ensure good arc starts, the end of the wire should be clipped. This removes any balled end that may have formed during welding.
• The travel speed for welding aluminum is faster than that for steel due to the high thermal conductivity of aluminum. If travel speed is not increased, excessive melt-through is likely on thin aluminum.
• Periodic inspection of the MIG gun and contact tip will prevent many of the wire-feeding problems associated with aluminum welding.
• Finally, store aluminum wire in a plastic bag to protect it from dirt and moisture.

Following these basic guidelines will help ensure quality welds on aluminum with the MIG process and your wire welder.

David Anderson is manager of retail sales for Hobart Welders, Appleton, WI.