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Old 12-20-2015, 07:27 PM
Dave Z. Dave Z. is offline
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Question Silicon Bronze Tig Troubles

I just bought a new AHP Alpha Tig welder and been practicing to get the feel of it. I have a motorcycle fuel tank project that needs tig welding. I split the tank to narrow it and also cut out the filler hole to move its location. Here's my problem. I made a patch to butt weld into the hole I cut to move the filler neck. I first welded in with steel filler rod and hammered and finished the way I wanted. It looked good. For the heck of it I sprayed soapy water on the weld and blew compressed air from the underside to see if I had pin holes. Well I had a ton. I ground and tried to fix them and welded from both sides. Still no good. A friend said to try Silicon Bronze over the steel weld. I did...and that weld actually penetrated to the other side thru the pin holes...so..I thought I fixed the leaks. No Go. It seemed worse. I even have pin holes THRU the silicon bronze. I ground out all the silicon bronze and cleaned it all the best it could be and welded again. Same result. I'm between 15 and 20 on my flow meter. Was using 3/32 tungsten. Set at 60 amps and pedaled it as I thought I needed to. Nothing I do produces a leak free weld. I cant purge it because its open to air both sides. I plan to use the silicon bronze rod to put the remainder of the tank together but as it looks it wont be leak proof. I do plan to coat the inside with a sealer but Id like to get it leak free and not rely on coating. A welder friend said I'm welding to hot....I tried to lower my amps but the rod just balls up. I have to dwell and move very slow to get it to flow. This in turn heats the steel the same as if I used higher amps and moved faster. So...any suggestions from you folks out there? I'm not an experienced tig welder. I can weld stick and mig and do build up welds to re machine worn parts where I work. So I do understand a bit about welding. I also noticed crud floating in the weld puddle and the finished weld has a dark color and looks dirty. Any help will be appreciated! Thanks!
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Old 12-20-2015, 08:28 PM
AllyBill AllyBill is offline
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Hi Dave

Are you using old steel TIG rods? It's a very common mistake. They look OK but the copper coat is shot and you'll get a porous weld every time. Are you running plenty of gas? On concave shapes like tanks I usually tap the pedal to get the gas flowing but don't arc-up first time around just to be sure of getting plenty of pre-gas onto the job. Arc-up boldly, give it plenty of pedal and get the filler straight in, bringing the heat up slowly sometimes causes pin holes if the weld isn't back-purged. Get a helper to pop a screen on and back-purge your weld from behind with some shielding gas and a hose, though you shouldn't really have to do that if you're getting good penetration. Be especially careful on the stop-starts of your welds. make sure you keep plenty of heat in the weld pool when you stop and let the post gas do its thing and likewise when you arc-up again before moving off.
After all that you'll still probably have a pin hole or two so find them with soapy water then pop a 1/8th drill through them before filling.


Will
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Last edited by AllyBill; 12-20-2015 at 08:28 PM. Reason: Forgot to say Hi
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Old 12-20-2015, 10:26 PM
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Marty Comstock Marty Comstock is offline
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As mentioned, its likely you dont have SiBr as that stuff flows nicely as a get out of jail free card. Only times I had issues with it is when I was welding dirt to rust and i kept stacking problems on top of problems.

One other time was when I was welding very thin copper with it. Not sure why that gave me fits, perhaps because the previous repair might have been silver solder, or something equally odd.

For that particular fix, I cut out everything suspect, and started over with good known material. Zero problems from then on.

I don't recall overheating SiBr when welding to steel, sometimes it takes more energy input because of the mass and the properties of the filler material.

Pics might help?

Marty
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Old 12-20-2015, 10:29 PM
Dave Z. Dave Z. is offline
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Thanks for the info. I pretty much did all that except the back side purge. The rods are brand new. I just don't get the fact that the silicon bronze rod didn't fix the leaks in the steel. I puddled the sb back and forth and made a wide weld. When I tested with air I could see the bubbles coming from under the weld edge and also right thru the bronze itself. Its impossible to actually see where the hole is when it bubbles along the line edge of the weld. Its as if the weld isn't bonded to the metal totally. That sounds weird but it gives that impression. I'm at the point now that I welded and ground this thing to many times and its all hammered and warped and I'm going to have to cut out this area and make a bigger patch. A welder friend told me I should be using about 25 amps with the bronze rod but that just melts and balls up on the steel. At 40 amps I can run a bead on a flat piece of sheet metal but it sits high and tends to get breaks in the weld. Higher amps and heat flow out the bronze but it looks as I may be heating it to much. I'm sorta hung up on using the bronze because it seems easier for my skill level. I got the impression the bronze would weld leak proof also. Can any weld be porosity free and leak proof without purging? Thanks again for the info....Ill keep practicing till I scrap the tank!
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Old 12-20-2015, 10:32 PM
Dave Z. Dave Z. is offline
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Marty...yes...they are SiB rods...both those and the steel were just purchased new. The steel was clean. I'm stumped.
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Old 12-20-2015, 10:35 PM
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Marty Comstock Marty Comstock is offline
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I have used it numerous times on radiator tanks, oil pans, all sorts of interesting applications, and haven't had the issues you are having.

I would go and melt it right with the molten steel, rather than on top of it. Give it more energy input, its not brass, no zinc to outgas and cause you grief. I often start at 100 amps and let my footpedal do the rest.

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Old 12-20-2015, 10:42 PM
Dave Z. Dave Z. is offline
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So you say that the steel puddles also? The SiB flows into the steel puddle? I sorta think I did that by how the back side of my weld looked. There was bronze on the backside. But....with that much heat how do you avoid horrible warping?
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Old 12-20-2015, 11:11 PM
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Marty Comstock Marty Comstock is offline
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Yes, you can actually weld it with molten steel, the silicon acts as a deoxidizer, helping remove porosity from a poorly welded joint. Its now compromised, in the fact that its no longer steel and not as structurally strong, possible cracking if its a mounting flange subject to vibration for example.

You are now beyond the realm of warping, its use here trying to plug pinholes and not simply trying to join two panels together. Usually when used in this manner warping is the least of a user's concerns.

I am not a scientist on this, I too am learning and am applying both what I have read in journals and from what I have observed using SiBr in this manner. Others may have different experiences or knowledge I am not privy to.

With that being said, the methods I use to this point have not failed me. Yet.


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Old 12-20-2015, 11:25 PM
Charlie Myres Charlie Myres is offline
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In one of Ron Covell's DVD's, he mentions that he once bought a bottle of contanimated gas, which gave him all sorts of grief until he substituted another bottle and solved the problem.

Try another cylinder,

Cheers Charlie
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Old 12-21-2015, 01:14 AM
fciron fciron is offline
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Your issue with the discolored weld and the porosity does sound exactly like the stories I've heard of contaminated gas. (Pure argon, right?)

I got a tank that was only half full last week, so I find the stories of bad gas a little more credible now.
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