4 Shielded Metal Arc Welding Copper Nickel Alloy Part 4 of 5

Section 4- Copper-Nickel Alloy- Shielded Metal Arc Welding

The Copper Development Association is pleased to present a series of video presentations covering the welding of copper-nickel alloy.  This video is the fourth in a series designed to provide welders with the principles of joining 90-10 and 70-30 engineering grades of copper-nickel. Here we consider Shielded Metal Arc Welding.
The shielded metal arc process is one of the oldest welding processes. However, inert gas processes are now used more extensively for copper-nickel welding.  The shielded metal arc process is an all-position process and is frequently used for fill-welding after a TIG root pass on larger diameter pipe. It may be used as the root pass for sheet or plate welds when the back-side will be back gouged. It is a good choice for field welding where the shielding gas can be blown away using the TIG and MIG processes.
Often the first thing a welder notices is that copper-nickel weld metal does not flow as readily as ordinary steel. It is more viscous or sluggish and does not flow as well. At first, this may be frustrating, but trying to correct this by increasing the amperage is not the answer. In fact, too high a current often leads to more problems and weld defects. The correct procedure is to stay within the electrode manufacturer's recommended current range, and accept the lower fluidity as being a characteristic of copper-nickel and nickel alloys.
Because of the lower weld metal fluidity, a more open weld joint should be used, for example by increasing the bevel from 30 degrees to 40 or 45 degrees for copper-nickel welds.
As with the bare wire used for the TIG and MIG process, the 70-30 copper-nickel filler metal is used to weld both the 90 -- 10 and 70 -- 30 alloys. The electrodes can be used directly for sealed containers without baking. The electrodes used in this video are 3.2 mm diameter.