Aluminum is a difficult metal to weld using standard hot welding techniques due to its high melting point, so it is important to know how to cold weld the material to effectively create a strong joint. According to PHLburg Technologies, although aluminum is 1.7 times less electrically conductive than copper, it is 3.4 times lighter in weight so it is an economically viable material to use as an alternative or welded together in combination. Producing the cold weld consists of a high pressure mechanical bond that causes a metallic flow between the two substrates and joins them together.
Wear clean protective gloves to prevent oils from your skin contaminating the surface of the aluminum. Due to the nature of metal flow in a cold weld, it is imperative to prevent oil, dirt and grease from touching the metal surface. Use a clean lint-free cloth dampened with mineral spirits to wipe the aluminum and remove all traces of dirt and grease.
Use an electric rotary tool with a fine steel wire brush attachment of less than 0.004-inch wire diameter. Position the wire brush on the aluminum surface where you want the weld, and abrade the metal to remove the layer of oxide. Repeat the procedure for the second piece of aluminum or metal.
Place the first piece of aluminum onto the mounting bed of a die punch. Position the second length of aluminum (or other metal, such as copper) over the end of the first piece. Create an overlap to the length you require for the cold weld.
Line up the overlap section so that it centers with the press head of the die punch. Clamp the aluminum into position using the die clamps.
Set the die punch to a minimum pressure of 10.5 x 103 kglcm2 or the equivalent of 16,000 psi. Activate the punch, and use one press of the die onto the overlap for a few seconds. Release the press to complete the cold weld procedure, and remove the single piece of metal. Increase the pressure to a maximum of 35 x 103 kglcm2 or 53,000 psi, in increments of 5,000 psi if the cold weld requires a higher pressure to join the aluminum effectively.
Apply a higher pressure to thicker aluminum and use lower pressures for thin aluminum, within the pressure range stated in Step 5.
Applying too much pressure to the aluminum will break it.