when you braze steel, how hot are you getting, do you have to
apply any flux to the metal pieces you are joining?
BJ, you can buy brazing rods coated with flux, but I can't recommend
it because the coating tends to crack and fall off. In my opinion,
it would be better to do one of two things. Either buy the black
flux which is available at welding shops and is stable at higher
temperatures than the usual flux for silver soldering, or buy a can
of dry flux meant for brazing and dip your brazing rod into it
periodically as you are brazing.
As to how hot you need to get, in order to braze, check the melting
point of the brazing rod. The metal you are brazing must get at
least that hot, in the area of the braze. If you are brazing large
pieces of metal, you will need an oxy-acetylene torch, in order to
get and keep the metal hot enough for the brazing rod to flow.
Hope this helps--