TiG Brazing how-to?

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I want to try TiG brazing, but my first attempt on 1/4" thick cast iron was spotty.  I was using 1/16" lanthanated tungsten, 110 amps, and 3/32" filler rod.  Most of the time the filler stuck and could not be knocked off with a slag hammer, but the bead was ugly, not like an oxy/fuel braze.  I read the Weldcote data sheet on the rod, and they suggested more heat and a larger tungsten.  I bought some 3/32" tungsten today and will try  175 amps as suggested by Weldcote for the 3/32" rod.How long should I heat the metal before feeding the filler?  I am going to guess I don't want to melt the base metal.Chris
Reply:Did you use flux?You're correct in that you don't want to melt the base metal.  Once you do, its not brazing anymore.  You only need enough heat to make the filler wet out, but it won't do so without flux if you're using a normal brazing rod.
Reply:Supe,I don't ever use flux with TIG braze.  Given that you've got the gas flow from the torch, you don't need the flux to protect the joint, and in fact you can have a problem with the flux outgassing and contaminating the tungsten.  You will need to ensure you keep the end of the braze rod under the cup to prevent oxidation.Chris, what is the base metal, and what is the alloy you are trying to braze with?  What is it's liquidus temperature (you should have that from the data sheet)  You only need to heat the metal long enough to get the filler to flow, and as Supe said, not the base metal.  Heat the base metal, and "stroke" the joint with the filler metal until the alloy flows freely into the joint, then move along just as you would doing O/A brazing.I r 2 a perfessional
Reply:Sorry, re-read your original and saw you were brazing cast iron...that answers the question about the base metal, duh to me...If you're using a silicon bronze filler, you should be able to braze it with no flux, DCSP with argon shield gas.  Use a gas lens if you've got one.I r 2 a perfessional