Standard silver brazing flux works fine on stainless steel, been
using it for years. It sounds like you are trying to use gold
soldering flux on stainless. I've done it in a pinch, but it took a
series of coatings and a lot of flux. In order to keep the
stainless from oxidizing quite so much, make sure the whole piece is
coated with the flux.
--- david thorp
I had a horse once whose mouth was too narrow for the snaffle I
wanted to use. I cut the stainless steel bit at one of the middle
joints and silver soldered it back together using green floron flux.
One day, while schooling in the indoor arena, the joint failed,
leaving me with half a bit in each hand, and the horse decided to
leave the building through a low door. I got plastered down low
enough in the saddle to keep from getting whacked by the top of the
door jam, and eventually got a hold of the bridle on the side of his
face and got him stopped.
The next day I tried again using paste flux for silver soldering and
the joint never failed again.
-- Spike Cornelius Portland, Or. RC ArtMetal