I used Ruby Fluid flux to solder #430 stainless steel and it worked pretty well.
I tried using two types of solder
- Chipquick RASWLF.015 and RASWLF.031 (SN-96.5% Ag-3.0% Cu-0.5%)
- Radioshack 60/40 rosin core solder (Sn-60% Pb-40%)
My process was as follows.
Scratch up the surface a bit. I used the stainless-steel tweezers at my workstation, but a bit of sandpaper would also work. Please note that I did some tests without scratching the surface and I couldn't get the solder to adhere. Scratching the surface appears to be essential.
Preheat the metal (either using a heat gun or the soldering iron)
Using a cotton swab apply the flux. This was Ruby-Fluid in my case.
Apply the solder using the iron.
The test samples appeared to come out good. I got good adhesion with both the silver-bearing solder as well as the regular tin-lead stuff. Once things cooled down, I could pull on the solder-samples quite a bit with my tweezers and the joints did not loosen at all.
I was actually surprised that the regular tin-lead solder worked. When I did some web searches on this in the past people were always saying that using silver solder was essential. But my test proved that non-silver-bearing solder can work also.
Also, if anyone was wondering, I made sure to clean off the soldering iron tip between soldering each test sample. Therefore, I am sure there was no significant amount of leftover silver on the iron when I soldered the tin-lead sample.