Aluminum's higher conductivity of heat means that it heats up faster than steel. This fact combined with aluminum's lower-melting point means that it's much easier to completely melt an aluminum work piece than a steel work piece.
Select a Lincoln Electric welding machine with the proper voltage. Aluminum welding requires a higher voltage than welding steel of the same thickness. A Lincoln Electric welding machine with 115-volts is adequate for welding aluminum of up to 1/8-inch thickness. A 230-volts machine should be sufficient for aluminum of up to 1/4-inch thickness.
Set the Lincoln Electric welding machine to provide a constant voltage when welding aluminum. Aluminum is commonly welded by spray-arc welding which sprays a stream of molten metal onto the base metal. This technique requires that an electrical current with a voltage that doesn't vary.
Ensure that the electrode feeder for the Lincoln Electric welding machine has larger contact tips. Aluminum expands more than steel when it gets hot, so the contact tips for aluminum electrodes will need be correspondingly larger. The contact tips for aluminum electrodes will typically need to be 0.015-inch larger than the aluminum electrode.