Copper phosphorus paste can be used in CAB furnace for boilers , copper phosphorus alloys can be used for
Copper or brass fittings can be brazed with copper phosphorus alloys, A.V.Saldature recommend special low-cost alloys and to use liquid flux provided by vaporizer (in some cases just as a protector flame), in this way you may avoid to use silver alloys that are much more expensive, and paste or powder fluxes that can be hard to remove.
CAB brazing furnace
Carbon steel resistance can be brazed in black furnace with copper paste, however this kind of resistance are not very common , stainless steel resistance can be brazed in brazing furnace (pure H2 or Na/H2) with special Ni Cr paste (9760M or 9760 M11WS – Ni 107) ,for alluminum resistance a an AlSi12 paste must be used
For manual brazing even if is possible to use brass alloys and flux in flame it is common to use a silver based alloy with an active flux as the D4P