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04-03-2012, 09:11 AM #1
TIG weld/braze W Silicon Bronze filler
I'm about to attempt a crack repair on a cast iron piece. It was recommended to me to use a silicon bronze filler to essentially braze it together. (w/TIG) anyway... i did a test on some old angle iron to see how this filler works and it was no problem and after doing both sides it proved to be as strong as the metal. my question is after the brazing the filler appeared black. I sort of expected to see a shiny brass look. a quick hit with a wire wheel and there was the brass look. is that normal? or is my argon flow too little or too much?
04-03-2012, 09:51 AM #2
About 20 years ago my boss at the time did some investigative metallurgy on Tig/silicon bronze - he had the right connections to get it done. He told me more or less the molten metals intermixed at the boundary and it wasn't just a "wetting" action like soldering. That's all I recall from many moons ago .
04-03-2012, 10:24 AM #3
You don't need argon for this kind of brazing. You could use a carbon electrode in your stick welder to achieve the same result.
oldbikerdude37 liked this post
04-03-2012, 10:50 AM #4
Dont. I just tried. the tig braze was awfull. use a black flux and a torch. Harris stay-silv black high temp worked well for me. Petersons #2 for cast iron is supposed to be better.
I had plans to gently and with low power use the tig to heat sort of like a torch. but the arc isnt stable at low settings. and at high enough steeings it burns the cast and the flux and the rod up. I tried with just argon, and I tried with argon and flux.
I too had tried on steel samples. not the same. they are thin and heat properly. the cast wont. Although.... I have done this long ago and had I though better luck? But my recent attempt was awfull.
the tig is to locally hot. it cooks the flux. cooks the rod. it hardens and enbrittles the cast. I have did it, but it was awfull, and a lot of gringing back out and a crappy joint in the end.
this is my thread on the welding web.
Si Bronze on cast iron exahaust manifold repair - WeldingWeb™ - Welding forum for pros and enthusiasts
04-03-2012, 11:00 AM #5
didn't use any flux...worked well. I was just curious about the black initial appearance of the bead
04-03-2012, 11:11 AM #6
Prolly a little carbon or graphite out of the ci
04-03-2012, 11:15 AM #7
the test i did was just on regular steel still could be carbon i suppose..probably will be worse on CI then
04-03-2012, 11:22 AM #8
I have been running into that and the sales rep stated that some of the chinese are useing graphite to lude there drawing dies.
Might be in the tig wire
I ran into it with red brass pipe not tig wire as it showed up eaven with silver solder.
04-03-2012, 12:52 PM #9
04-03-2012, 01:12 PM #10
I realize that this is kind of a moot point since you have already fixed your problem but I have had to weld a lot of cast iron in my time and I think the very best way is to use a stick welder and nickel rods. I have an old buzz box I keep around just for doing cast iron. If you can preheat with a torch so much the better but the trick I have learned is to skip weld the crack and not use one long continuous weld. Then come back and fill in between the welds. I have welded cast iron using this method for many years and have had very good results. The rods are a bit pricey but worth every penny.
MichaelP liked this post
04-03-2012, 01:21 PM #11
we have a new miller tig welder we paid $5,000+ for it but I would just use a torch, a can of brazo flux and get it done.
I do lot of old school stuff, for example some old cracked diesel exhaust manifold. I clamp the whole unit to a semi flat plate. heat the whole thing nice and hot. then hit it with a torch and rod and its done real quick .
When it comes to cast iron tig is the last machine I use. that's just me, you can do it your way.
cg285 liked this post
04-03-2012, 01:42 PM #12
I've done some TIG and MIG brazing. It sounds like you're overheating it -- once you get the right temperature down, it just flows like honey.
This is aluminum bronze TIG brazed onto cast iron:
04-03-2012, 02:03 PM #13
04-03-2012, 02:40 PM #14
I've used spools of aluminum and silicon bronze as TIG filler rod. There was nothing special to it.
Running bronze wire in MIG is a little trickier -- if you run too hot, the wire explodes with a green *splat*. Too cold, and it balls up on the surface.
04-03-2012, 03:04 PM #15
Some old cast iron defies welding, especially exhaust manifolds, it can act like dirty steel wool when the arc hits it. I've welded plenty of cast iron with TIG and silicon bronze rod, it's easier than nickle rod. Sometimes you can splatter stuff together with nickle rod and a stick welder that you can't do with a nicer process but the result is nasty looking and not too strong.
04-03-2012, 04:51 PM #16
not moot yet ! that was just a test on some steel. I thought it flowed quite nicely and after i tried to break the weld by bending and only the steel around it bent, but not the joint. the black on the bead must be contamination of some sort but as far as i can tell it doesn't seem to hurt anything. ill just clean it off!
04-03-2012, 04:57 PM #17
FWIW i am now hooked on Cast Iron wire for my mig with Argon.
http://www.crownalloys.com/TechSheet...ew_Warning.pdf I welded my Geo Metro exhaust a few months ago it took aprox 35 seconds to weld and i have over 5,000 miles on the repair which is still perfect. I did it on the car took a die grinder to knock off the rust, drove it for 15 minutes to warm up the manifold, welded it uphill with about 30 overlapping tacks let it run for another 5 minutes and shut it down. I did it like that bacause thats the normal cycle of the manifold when driving. Well worth the 75 bucks for a 2# spool. Just my thoughts...BobBob Wright Metal Master Fab
Salem, Ohio Birthplace of the Silver and Deming Drill, all others are copies.
04-03-2012, 05:39 PM #18
this was a old exhaust manifold I was repairing this time. dirty steel wool about sums it up. but I had good results with the oxy torch.
04-03-2012, 10:42 PM #19
You can take a nickle ectrode and clean all the flux off of it and use it to tig weld cast iron. It gives great results too.
But I've always stick welded cast iron. Some cast will be a headache and some weld beautifully. The trick is to heat the area with a torch then weld short beads, then chip and peen. Keep welding short beads till you have it completed. If it doesn't flow very well grind it out and keep welding over it again untill it's starts flowing smoothly and looking uniform.
jackal liked this post
04-04-2012, 08:10 AM #20
In my experience with cast iron, ox-acetylene brazing and nickel 99 rod with TIG, it's all about heat and temperature control. I've pretty much used exclusively the nickel 99 and TIG for the last few years. The problem I've seen and pretty well learned to control is that at the right temperature everything works nicely on most cast iron. Too hot and the iron gets foamy on the surface and the filler won't stick. And of course, if the iron is too cool the filler won't stick either.
The only time I could absolutely not get it to work was on an old wood stove part that had been in the firebox for several years. No matter what I did the iron foamed and disintegrated before it got to the plastic stage. Still, I dabbed in the nickel rod and filled the joint. It looked pretty crappy and I didn't think it would hold much more than its own weight, but it made it through one heating season so far.
FWIW when I TIG it I use no flux. I just grind it out almost all the way through and then start puddling in the nickel.