I am trying to resistance weld two 1100 aluminum ribbons together. one is .036 inches thick and the other is .063 inches thick. I have tried various settings such as 31000 amps, 4 cycles, and 850 lb. which seemed to provide a decent connection, but with varying lug sizes. I am looking for a consistant .20 inch diameter lug or larger. The weld is going to be souly an electrical connection, so deformation will not be an issue.

The electrode I used is copper 5/8 inches in diameter with a 2 inch radius. Truncated electrodes seem to have the same problems.

Can you help me determine the proper weld schedule/electrode to provide a minumium lug of .20 inches in diameter?

Thanks for your help.

Jeremie

-- Jeremie Buday (jeremie_buday@lincolnelectric.com), June 03, 2004

Answers

Dear Jeremie: By using our "Heat Clips" made of stainless steel you can weld aluminum. The stainless steel will increase the resistance by the tips without blowing a hole.

-- Lennart Naslund (datawelder@prodigy.net), June 03, 2004.

If you are getting a weld but it varies in size, one key would be aluminum surface treatment. Some aluminum surfaces are very unstable in the air and form an unstable oxide. A stable oxid is bohmite (I think that is the word but not sure of the spelling). An unstabel oxide is bayerite (again I think that is the word but not sure of the spelling). Processing of the aluminum forms a stable or unstable oxide. For example, hot water rinse in the aluminum mil will contribute to an unstable oxide. Where as cold water rinse will contribute to a stable oxide. Note that hot water rinse is often done to speed processing for drying off. Many other factors contribute to a stable or an unstable surface oxide. Handling of the aluminum ribbon can affect it. Many years ago, an aluminum weld variation in an aircraft application was found to be coincident with the menstal cycle of women material handlers.

Alodine 1200 was an example of a process used at General Dynamics that formed a stable oxide that was very weldable inspite of environmental effects. Today the aluminum companies have several methods for processing aluminum in preparation for resistance welding. If you have not already done so, contact your aluminum supplier mil to see if the preparation of the aluminum tape can be improved.

The previous suggestion using stainless is a good one. The starting current also has a profound effect on the formation of a uniform weld in aluminum. Some applications need a low starting current. An example is a weld bonding application on one of the military aircraft. Some need a robust starting current. One applicaton is the all aluminum lift gate in the GM suburban.

Only testing can reveal that answer. In addition, some weld controls have a variation in starting current that can contribute to weld variation. Some constant current controls start out at a value that is a function of the previous weld. That is a tough one to sort out without welding machine instrumentation.

We are coming out with a new book shortly that describes how to develop a weld schedule. It may provide some benefit in your case. It provides a procedure for weld schedule optimization.

If an unstable oxide occurs on the aluminum and you have tried a bunch of stuff such as above, I doubt if there is any weld schedule that will make repeatable weld sizes. That is the nature of aluminum.

Bo

-- bob szabo (bob@szabopublishing.com), June 15, 2004.