Copper and copper-nickel alloys are commonly welded using the manual metal arc technique which uses a stick electrode that has been coated with flux. This is a generally inexpensive welding process, but it requires using a metal inert gas which is faster and a tungsten inert gas that when used will produce strong welds.
You will want to use a 70 – 30 copper-nickel filler when welding alloys that are at least 70 percent copper. The high nickel content will produce a much stronger weld than other types of filler metals. In order to measure the strength of the weld that will created, you can use a longitudinal bend test. This will help you see how the integrity of the weld will hold up once your weld is completed.
Next you will want to thoroughly clean the material that is going to be welded. This needs to be done in order to remove any contaminants that can cause the weld area to crack. It is important that all traces of lead, phosphorous and sulfur be removed from the copper prior to welding. These contaminants can commonly be found in cutting fluids, grease, oils and paints. Copper-tin-zinc alloys have been proven to contain these elements and should not be used when welding to copper-nickel alloys.
When welding copper-nickel that is less than 3 mm it is suggested that a square butt be used to prepare the weld materials. If you are going to weld copper-nickel that is larger than 3 mm it is suggested a beveled preparation be used. If you are going to be working with carbon steel you should make the included angle wider, typically more than seventy degrees. The weld metal does not become as fluid as that of carbon steels and typically requires more manipulation with the electrode to make it fuse with the side walls of the weld area.
If possible, when welding copper, you should weld down-hand. This allows for a greater rate of deposit and is a better technique for beginner welders. If the piece that you are working on is larger than normal, sub-assemblies should be used for down-hand welding instead of welding in a less favorable or more dangerous position.
It is possible to perform flawless welds when working with copper, all you need is practice and finding the best technique that works for you. Welding copper can be a tricky undertaking, but it can be done when the proper guidelines are followed.