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Old 01-29-2018, 03:23 AM
Andy Andy is offline
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Join Date: May 2016
Location: Recklinghausen, Germany
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Quote:
Originally Posted by Stretch View Post
Hi Richard.

For aluminium (16 gauge) I would highly recommend trying either a no5 or no7 BOC style (UK) welding nozzle and, most importantly, turn the gas pressure down to 2-3 psi max. You want a soft, fat flame. A lot of beginners make the mistake of running a too narrow flame cone, with higher than necessary flame pressure, which inputs too much heat into a thin weld zone causing burn through. Also, you have to weld aluminium at a very quick pace with oxy-acetylene. We are talking almost feet per minute as opposed to inches per minute a la steel. This is where the true art to gas welding ali comes in to form. Fast, fast, faster!

I seldom add rod to the puddle on ali body panels - for me the rod is there literally to start the weld then finish the last 1/4" of weld.

Also, I was taught to oscillate the torch in continuous circles to the width of approximately 1/4" - 3/8" around the weld zone as you move the torch along its path. This, apparently, was the norm during WW2 era to decrease the intensity of the heat affected zone according to my mentor. It is said to even out the h.a.z. a little, which reduces stress. This method, with good practice, should produce a lovely, flat bead with perfect penetration: A weld that needs no filing and only planishing or wheeling to make the weld virtually disappear.

Don't get me wrong, there are many ways of gas welding aluminium, but this is what I was taught and I find it works fantastically well.

On a side note... and this is one that's sure to raise eyebrows: I only flux the edges of the metal and not the full width of the weld bead. I find there is more than enough flux on just the edges to facilitate a perfect weld. The advantage is that flux glare is massively reduced and you have a more even temperature distribution. Again, a nugget that was passed down to me during my apprenticeship in the 1980's.

Regards, Matt
Very interesting. I must say I never had any problems welding over tacks (I do the tacks without welding rod). My welding method is that I use a flux coated strip cut off the aluminum as a rod and flux the edge and a very small area around it. Tried only fluxing the rod and just the edges...works for me but I like to play it safe. The gas setting is low...way lower than for steel. Yes, weld speed is fast, but it slows down on bigger panels. I can't really say how I adjust the flame...I do it by the noise it makes. I make small adjustments by altering the torch angle or by raising the flame when I see mischief building up in the weld-puddle.

An old german aircraft guy told me to keep the flame stady, not rotate it. I will try the rotation method next time. And he told me to weld right after the tacks, no cleaning and refluxing. Again...works for me.

I use blue welding lenses and I use the welding rod all the time because I want a nice raised bead that I usually file down a little, then lightly hammer it before planishing it. The hammering is said to improve weld density...that is what an old german aircraft book from the 40s says.
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Cheers,
Andy.

If nothing goes right, go left!
Is fhearr fheuchainn na bhith san duil. (It is better to try than to hope!)
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