O/A welding aluminum

I've got a busted (H-D motorcycle) transmission case , cast aluminum . It's busted too bad to repair and use , but will be a good practice piece for me to learn on . I recall dad telling me that special goggles are needed , to see the al as it reaches the proper temp without melting the whole thing . What kind of lenses do I need ? I also need a recommendation on filler rod , and anything else y'all can think of that I need to know . One thing I have learned here is that oxidation is a major problem with al , and cleanliness (oils, etc) is extremely important . Not likely I will do this very much , but it would be a valuable addition to my skills . Might even get good enough to weld up and retap that stripped spark plug hole in my rear head . Inserts are a pain ...

Snag,
One way to clean up a casting is to bake it. This outgasses the oil and other contaminants that may be in the aluminum. Big problem with cast aluminum is the alloying components (silicon, copper etc.) can come to the surface just when you are trying to lay in some aluminum rod. Another issue is sand contamination, but you can usually get past this with some serious grinding. I've always used TIG to weld aluminum as I think it is easier to see what you're doing and I can get more localized heat where I want it.
Let me know if you get Oxy-Act to work. I'd test it to destruction to see how good of a weld you produced.
Bart
Bart D. Hull snipped-for-privacy@inficad.com Tempe, Arizona
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Snag wrote:
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Bart D. Hull wrote:
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I'd love to get a tig set-up , but it just ain't in the cards right now . Saving my pennies for a set of aftermarket cylinder heads ... Thanks for the advice , I understand now why the guy who welded some stripped holes on another bike /part baked it a couple of hours .

"Snag" wrote: (clip) What kind of lenses do I need ? I also need a recommendation on filler rod , and anything else y'all can think of that I need to know . ^^^^^^^^^^^^^ I used to use cobalt blue lenses, but they are illegal now, since they do not protect the eye from UV. I don't know what has taken their place. In welding aluminum with oxy/acetylene, the lens cuts out the bright yellow from the flame, which makes the weld hard to see. You need flux that is specifically made for aluminum. You need to make sure your work is supported, because as it approaches the welding temperature, it becomes "hot short." This means that it will fall off without warning.

Leo Lichtman wrote:
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This is what dad was talking about , the "hot short" situation . Is part of the solution to use a filler with a slightly lower melting point than your workpiece ? I thought the blue goggles were to enable you to see that you were approaching the melting point of your workpiece ...

"Snag" wrote: This is what dad was talking about , the "hot short" situation . Is part of the solution to use a filler with a slightly lower melting point than your workpiece ? ^^^^^^^^^^^^^^^ If your rod melts at a lower temperature than your workpiece, you are *brazing.* That is a way out, and is what I do when the workpiece is so delicate that I'm afraid that when it starts to melt it will be destroyed. However, welding castings, like cylinder heads, you ought to be able to bring the edges of the weld up to temperature while the bulk of the metal supports it. ^^^^^^^^^^^^^^^^ I thought the blue goggles were to enable you to see that you were approaching the melting point of your workpiece ... ^^^^^^^^^^^^^^^^^ When you apply the flame to the aluminum, the almost colorless bluish flame starts to go bright yellow, making it hard to see anything else. The cobalt blue goggles (or whatever is used today) filters out this blinding yellow light. But this is not how you know the metal is about to melt. With aluminum, that's a little tricky. You can't go by the glow, as you do with steel. Watch the surface of the aluminum very carefully, and just as it is getting ready to flow, it becomes smooth and shiny. Don't worry--as you practice, if you don't get it right the first time, just try again. You're only practicing, after all. ^^^^^^^^^^^^^^^^^^
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Well I went this route a few years ago with some success. What I did was to get the aluminum flux for OA and flux cored aluminum rod. The flux goes incandessant when it gets just about where you want to be welding (temperature wise) and the regular green goggles were just not making it. I grabbed a pair of yellow shooting glasses and stuck them inside the green goggles. I think a pair of the yellow sunglasses would work too (with the regular welding goggles). I was able to do some pretty nice welding with this setup. One trick for seeing the temperature "kick" is to soot the weld area with the torch before you start. The soot starts to crack and then sorta goes away and you are at the right temperature. After a few trials this way I was able to tell when it was right without sooting things up first. It is tough to get used to the wait and wait for it to be hot then go like hell to keep up with the meltdown :) I also had best luck with a slightly carburizing flame. This probably isn't even close to the right way to do it but it worked for me :) Glenn

in my limited experience w/ OA Al welding, another method of judging the right temp. was to watch the flux.
I used a powder that you mix with a little water till you have a toothpaste consistency, apply it to the piece(s) and apply heat w/ a carburizing flame. the flux will first dry out as the water evapourates, leaving a powdery crust, then after a period of time it will go back to a liquid appearance....thats when I would start to weld. mind you , I was using a feathering technique i.e. lots of pre-heat....still got some great looking welds in flat and T.
about the blue lenses and the comment wrt not blocking UV....I never used them but as far as I know, OA welding does not produce any radiation other that visual spectrum and IR (heat). yes, its bright but not damaging. thats why you can use a #5 shade. so if others swear by them (the blue lenses) for welding Al...letting you see the ponit when the metal begins to flow....go for it. if you can find them, I guess.
-mark

"mkzero" wrote: (clip) so if others swear by them (the blue lenses) for welding Al...letting you see the ponit when the metal begins to flow....go for it. if you can find them, I guess. ^^^^^^^^^^^^^^^ That's the point. They are not available, as far as I know, because of the risk of eye damage.

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well, I guess its a moot point then.
though I'm certain that theres no risk of UV with OA welding. intense light does not necessarily equal UV. one can braze w/o using a shaded lense, using a propane torch and brazing fuel. one can also braze using an A/O torch and a carburizing flame. the process is the same: oxygen and a fuel are being combined and burned, mind you the carburizing flame is brighter but still not a UV emitter. but again, if they're not available then thats that. can't argue them on to the shelves.
-mark

"mkzero" wrote: (clip) I'm certain that theres no risk of UV with OA welding. intense light does not necessarily equal UV. (clip) ^^^^^^^^^^^^^^ I don't doubt you on that point, so now I wonder why they were banned. Does anyone here know?

Leo Lichtman wrote:
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For the exact page go to; http://tinmantech.chainreactionweb.com/html/tm2000.php?cart Ç5115b722740b256e20a6f2df811677
I hope that link works.
It is on the tinmantech site under welding > eyewear.
Covers the subject pretty well.
michael

"pipedope" wrote: For the exact page go to;
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http://tinmantech.chainreactionweb.com/html/tm2000.php?cart Ç5115b722740b256e20a6f2df811677 ^^^^^^^^^^^^^^^^^^^ Thanks, Pipe, that ws interesting. However, their entire discussion seems to gloss over the exact point we were arguing. They point out that that glass blowers and welders were suffering eye damage from the lenses they were using, but it is not explained what was causing the damage. I am still wondering---is there something about sodium yellow that is harmful?

I have one of these lenses and it works great for gas welding aluminum.It allows you to see the puddle clearly. It also works for gas welding in general. http://tinyurl.com/f44aw
miguel

Another trick to welding Al is to warm the pieces up in an oven to about 400. It helps me with MIG on Al.
Jon
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The expert of o/a welding of aluminum is best researched at: www.tinmantech.com
Good Luck.

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The best lens is the TM2000 dydimium lens from www.tinmantech.com
They're pricey, but they really work. They completely eliminate the sodium flare from the flux so you can really see what you're doing. If you can't see what you're doing, you're just guessing at when the metal is starting to melt and you'll usually end up with a mess.
You also need flux. The same place sells a very good aluminum flux. The flux must be removed with hot water after welding because it is corrosive.
Most cast alloys weld pretty well with 4043 filler. I sometimes use 1100 filler (more ductile) if I'm having problems with cracking, as in when I'm too lazy to do enough preheat of the entire casting.
Where gas welding really shines with aluminum is when doing sheetmetal. The welds are more ductile than TIG or MIG welds. The welded metal can often be planished and otherwise worked after welding. Guys that do custom auto building like Kent White and Ron Fournier use gas for that reason.