Chances are if you have been looking for work as a pipe welder in the ship building industry, you have been asked if you can weld copper nickel or CUNI pipe. Well, the reality of this metal is that it welds almost like stainless steel with one exception. That is copper nickel is easier to weld than stainless steel because it takes the heat from the arc much better.
This metal uses almost the same amperage settings with one main issue. Cold lap can be a problem when welding because it is difficult to see penetration. The weld puddle looks like it is penetrating and the weld looks like it has flowed into the joint but there may be spots that have not. Copper nickel absorbs heat very well so it is fine to weld it on a higher amperage setting. Another common issue when welding CUNI is travel speed. The weld should have a copper color to it just like stainless steel. The actual weld puddle has the look and feel of stainless steel and aluminum at the same time. Many welders describe the puddle as “muddy” because if you travel too slowly the pipe will have a dirty appearance that is almost like a soot coating.
In the end, CUNI pipe is easy to weld and all of the big fuss recruiters make about welding experience is blown out of proportion. Most welders who have never welded this metal will be able to certify with just a few hours of practice.