Selecting solder

Steel and cast steel:

All silver solder can be used for soldering steel. For soldering tool  steel, the usual preference is to use as low a bonding temperature as possible, and we recommend starting with silver solder S-44 or S-55.

Stainless steel:

Silver solder S-55 is recommended for soldering stainless steel, since it is a good colour match and has a low working temperature.

Nickel and nickel alloys:

Use silver solder S-44 or S-55.

Copper and copper alloys:

All solders are usable. For soldering pure copper, use S-2-K (Heating and plumbing solder) or S-5-K, (the silver content improves the flow, fluxes are required only for soldering copper alloys such as brass).
For brass, the easiest method is to use silver solder e.g. S-44 or S-55 FC.