Braze welding.

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I'm curious if anyone has some pointers on braze welding mild steel with brass.I'm in the middle of a two week (not nearly long enough) welding class at my A&P school and Im stuck on a brazing project. I'll add that I have about an accumulated years worth of experience with silver soldering and an acetylene torch on brass, copper and silver from high school and that's about as extensive as my experience remotely related to welding goes. We're supposed to take two (maybe 1/16") 1-2"x4" mild steel rectangles and braze weld them together. I file the ends flat on a flat file and scrub the edges near the ends with a Brillo pad as far as prep goes. I can do tack welds on the ends fine but I can't get any penetration in the middle and Im having trouble getting the puddle started as I go across. I'm thinking maybe the middle is getting too hot (no more than a dull red) during pre heat and the gap in the center is getting too small for the brass to flow into. Also our tubes that hold the flux to dip the wire in are only about an inch deep so a large chunk of my time is focused on redipping the rod into the flux instead of focusing on my bead. Would it be a bad idea to just run the flux along the gap instead of bothering to go back and fourth with the wire?Edit: Were also using some pretty worn out torches and regulators. I'm using an O tip (though it's probably bigger than that from over zealous cleaning) with a slightly oxidizing flame.Last edited by AGreenSmudge; 08-14-2009 at 08:51 AM.
Reply:Some pictures would help, but you shouldn't have much trouble getting brass to flow thru the joint on 1/16" material.  Just for the record Brazing is not welding.  It is a bonding process just like solder is, and not a fusion process like welding.  How large of a gap are you using?  what size tip, and what size rod?I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Hammack, Actually the term "braze welding" does exist, and is different than "brazing". Braze welding is using a fillet of filler material for strength ( tee joints ) , while brazing uses lap joints and capillary action.
Reply:Originally Posted by makoman1860Hammack, Actually the term "braze welding" does exist, and is different than "brazing". Braze welding is using a fillet of filler material for strength ( tee joints ) , while brazing uses lap joints and capillary action.
Reply:Originally Posted by AGreenSmudgeI'm curious if anyone has some pointers on braze welding mild steel with brass.. . .Im stuck on a brazing project. I'll add that I have about an accumulated years worth of experience with silver soldering and an acetylene torch on brass, copper and silver... . . .I can do tack welds on the ends fine but I can't get any penetration in the middle and Im having trouble getting the puddle started as I go across. I'm thinking maybe the middle is getting too hot (no more than a dull red) during pre heat and the gap in the center is getting too small for the brass to flow into. . . . Would it be a bad idea to just run the flux along the gap instead of bothering to go back and fourth with the wire?
Reply:Originally Posted by Hammack_WeldingSome pictures would help, but you shouldn't have much trouble getting brass to flow thru the joint on 1/16" material.  Just for the record Brazing is not welding.  It is a bonding process just like solder is, and not a fusion process like welding.  How large of a gap are you using?  what size tip, and what size rod?
Reply:Originally Posted by denrepDoesn't take much flux. Good idea to  flow the flux out; then as you're tinning the joint, scrape the filler rod's tip through the flux with heavy pressure on the metal. Warm the filler rod some, but keep the rod mostly out of the flame. Heat the work just enough so that scraping the filler rod's tip on the work barely rubs off melting filler; then your temp is almost "there" for tinning and running the bead.Sounds like you may be overheating and "baking" the flux. Use the same tinning flow techniques as for solder. A heavy black residue on the areas that won't tin is a sign of too much heat.Good Luck
Reply:If its only turning a dull red you might not be getting it hot enough.  Since your trying to braze weld, you dont have to worry about not melting the base metal.Have we all gone mad?
Reply:It's probably obvious, but make sure you have a neutral flame.