I just ordered some bare Allstate 11 brazing rod and while I hope to tig braze with it, I also bought some powdered flux. In highschool, about a million years ago, I think that we just heated the rod a bit and dipped it into the jar of flux. But what is the proper technique? I gather from Ernie that you don't need flux when Tig brazing.
None flux with tig. As your age-addled brain recalls, flux with bare rod when gas welding.
With tig, use silicon bronze. I first tried to tig with bronze rod for gas welding. I thought I'd just bust off the flux coating and give the rod a buff to get it all off. The result was awful and included a zinc-like smoke and haze.
When you get the right bronze, you will really like tig brazing. Anyway, I do and am grateful for getting turned onto it by the folks here.
The only problem with using copper coated filler rods is if you are welding parts for nuclear (or as Bush says "Nucular") reactors. The copper particles in the weldment can retain radioavtivity if exposed to radioactive materials.
Other than that there is no problem with copper coated filler metals of any alloy. The purpose of the copper is to prevent rust.
Well, I "used" to believe that..............I've since found out, however, that copper and steel won't fuse. Like a copper heat sink, etc. I've read (you *are* a teacher, right?:), The experimental aircraft association recommends only uncoated wire for this reason. (OA on chrome-moly tubing). They say that the copper is there so it can be run through a die and for lubrication. Naturally, all this contaminates a weld. You're right however, in that it *does* work, I've used a bunch of it. Another thing is that breathing copper is worse than zinc, as it cumulates in the body.............
Now, I'm not trying to start something, but am just trying to sort through the information available. IF, copper is there strickly because the mfg is easier, then maybe I should just use 3/32 rod at the rem yard for filler....what say you?
Well ACTUALLY the best way to join Chrome-moly tube is with a TIG using ER80S-B2 filler rod. Gas welding works, but TIG is faster, cleaner and of equal strength.
Yes I am a teacher, and I read a LOT about welding research. Copper poses no threat to the strength of your welds, or your health unless you are eating chunks of it for lunch. The amount of copper on welding filler rod is absolutely tiny and almost all of it is vaporized in the gas flame or welding arc. If Copper weakened welds then the entire aerospace industry would only use bare rod. Bare rod is used, but usually only where there is a chemical interaction problem with copper and some alloying element in the steel, or the aforementioned problem with radiation.
I have welded a lot of 4130 a LOT of different ways. Bike frames, air frames, motorcycle frames, race car frames. The most important part about welding it is simple welding skill. Any decent TIG or gas weldor can weld chrome-moly. It is not voodoo, just proper technique.
If the experimental aircraft association wishes to live in the dark ages, gas welding 4130 and burning witches, I wish them the best of times.
Personally I like to do things in the most effective manner.
And yes I am sick and tired of 4130 being touted as such a difficult material to weld. It is one hell of a lot easier than titanium, and I have lots of fun welding that stuff too. For that matter welding food grade stainless tubing in breweries is about 10 times as hard as welding air frames.
Get good at your technique, stop woorying about copper contamination, and start making planes.
When I was learning to braze, I was told to watch for the flux to start flowing as this was an indication that you were near the proper temperature for brazing. I've watched plenty of people stick the brazing rod in before the flux is flowing and get it stuck. I was just curious how close to brazing temperature borax would flow.
Well, I got my Allstate 11 rod, only availabe here at least as a special order. Minimum quantity was 10 pounds. They shipped the right flux - Allstate 1113 - which I was really worried about, expecting some normal flux. What really got me was they shipped flux-coated rods, when I specifically and at great length ordered bare rods (why flux if the rods are already flux-coated?). I kept the flux, even though they were happy for me to return it when I called to chastise them for getting the order wrong. Maybe I'll make something where I want to braze into a lug or something, where that sort of flux will be a help.
Anyway, getting set up to repair my car chassis (all of this is to repair a bent rad support on the race car) took about an hour, unbrazing the bent tubes, straightening them, cleaning them, fixturing them to re-attach. Brazing them was getting the flame as low and soft as I could, low PSI on the gasses, gently heat the pieces, flow the braze material in, build up a nice fillet so that they look just like old-timey nickle bronze welds. Not overheating was key - back the torch away as soon as the material seems too hot. The welding took about 15 minutes, I really took my time and didn't rush.
Out of my 10 pounds of brazing rod, for which I paid about $300 Cnd, I now have 29.9 pounds left over - I used ONE rod. I now will be looking for projects that cry out for brazing, where I used to look for things to Tig weld...