Fabrication of copper-nickel alloys

Fabricating 90-10 and 70-30 copper-nickel alloys is straightforward; they are ductile and easily formed although they require a higher degree of cleanliness than for steels. Machinability is similar to that of aluminium bronze, phosphor bronzes and other copper alloys that do not contain free-cutting additions. They can be welded and brazed using most standard processes.

TIG welding 90-10 copper-nickel. Photo courtesy of Eucaro Buntmetall GmbH.

70-30 welding consumables are normally recommended for both alloys, as they offer superior deposition characteristics and the corrosion resistance is at least comparable to each of the base metals. Both flux-coated electrodes and bare wires can be supplied to recognised specifications and have added titanium to avoid porosity.
For welding copper-nickel to steel, 65% nickel-copper consumables are used so that the weld metal can absorb more iron dilution from the steel without cracking than copper-nickel weld metals. When brazing, silver–based brazing alloys should be used rather than phosphorus-bearing ones.

Rotary draw bending 90-10 copper nickel pipe using a mandrel. Photo courtesy of Eucaro Buntmetall GmbH.

No heat treatment is necessary after welding. Post-weld clean-up is not as critical as it is with stainless steels. All traces of spatter and slag should be removed and the weld may be cleaned using a stainless steel brush or rotating flap wheel to leave a bright finish.

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