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#1
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Problems with O/A welding AL
Hey guys,
Already posted this at another site...some of you might have seen it. I have a small but annoying problem that slowly drives me mad. Perhabs one can solve the mistery. What I am trying to do is gas welding aluminium. The sheet is 1,5mm 1050 H14. Well, I get it to join and the weld is always good, but there are those 'craters' in the top of the weld. Here is what I do or did: I clean the sheet with acetone, brush it with a stainless steel brush (always after I cleaned it), apply the flux with a brush that has no steel parts and treat the filler rod the same way. Needless to say that my working space is ultra clean and I use some stands to keep the brush, filler rod and the parts off the bench. Tacking and welding is done with a Minitherm Tip No. 2, one size bigger as I would use for steel. The flame I use is slightly acetylene rich, I use the sound of the flame to adjust the heat but one could say that the inner cone is roughly 3 times longer than the thickness of the metal. Tacking is done hot and fast, vertical tip. After tacking I do not re-flux but weld right away. The weld holds, wacking it with the biggest hammer does not crack it. But here is what it looks like: 20170819_144536.jpg And the root: 20170819_144559.jpg Here an other example but with a different type of flux. Still ugly but much better: 20170903_123928.jpg Root: 20170903_124436.jpg Can that really be dirty acetylene? Since the root is not affected? Oh, cleaning after tacking and refluxing does not change anything. For now I grind down my welds because I need invisible welds but there might come the day when I want a nice looking weld that is not planished. So...what do I miss...where is my fault? Cheers, Andy.
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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!) |
#2
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Oh...I use a SS 'toothbrush' only for cleaning AL...nothing else. Also I clean and brush the rod prior to coating with flux.
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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!) |
#3
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That weld is pretty good Andy, maybe a flux issue or your flame is to hot (back the Oxygen off a little), also the heat zone on the alloy appears grainy, so maybe your sheet is oxidised. Been a while since I welded Ally with O/A so thats all the help I can give, there are many others on here that are pretty good and should be able to help you.
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John EK Holden V8 |
#4
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Quote:
Hi Andy, When the top is dirty and the root is clean .... then you have dirty gas. Think about it - what is the one thing that only touches the top side of the weld? The flux flows to the root side. The filler dilutes and mixes through. Dirt / contamination will mix through, unless it is coming from the torch and then it lays on top. Oh, I would discontinue the acetone. It is expensive. It goes into your liver in 20 seconds after contact. 91% Isopropyl works as well for this, is cheaper, more available and is non-toxic in this application. Dirty gas showing on top of O/A gas welds: P1160609copy.jpg Root sides of same welds: P1160610copy.jpg Filter that fixes the problem: P1030224 copy copy.jpg Source for this filter: http://www.tinmantech.com/products/w...lding-filters/ Filter element will last for 2-3 years with daily use. Using a primo flux will help, but the problem will not go away by just changing the flux. Your welds are nice. Get some clean gas and they will be nicer, always. Dirty gas is becoming more prevalent across the US because Airgas kept using a nasty decrepit acetylene generation plant for 10 years, and all those 1000's of bottles are still dirty and are becoming saturated into the supply chains across the US.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#5
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Can it be something else? In this picture the weld doesn't look dirty to me but brittle.
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Richard |
#6
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I f*****g knew it. (Sorry, sometimes I can't hide my Irish heritage)
The gas has been the only thing I did not change right now. By the way, the second weld, the one with much less pitting was made using your premium flux, Kent. I tested a lot of different flux (fluxes?) and yours works pretty well. Will stick to that. The weld looks brittle but I could hammer it like mad, hammer it back the other way, then flattened it out again. Then I folded the sheet up onto itself along the weld, straightened it and folded it the other way. That was when the first cracks appeared...at the edges...next to the weld. The pits are just in the top layer of the weld. Ground down it is all solid. Here are pictures of a little 'hood', made from two pieces, weldline is in the middle: 20170802_225447.jpg 20170802_225445.jpg 20170802_225440.jpg The upside of my 'quest' to get rid of the pits is: I learned a great deal about O/A AL welding. I am still very far from knowing it all, but I don't get scared anymore. Well, as my acetylene is running low, I will try my luck with a different supplier. There are not many left back here in Germany. If that does not do the trick...I know were to get the filter, Kent. I am flattened that everyone speaks of my welds as 'nice'... Cheers, Andy.
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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!) |
#7
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Hi Andy, is this the first time you had this problem? I thought dirty acetylene wasn't an issue over here in Europe.
By the way, indeed beautiful welds. Man, the root is just as nice as the top Cheers Richard.
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Richard |
#8
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Yes, the flux floats the "smut" to the surface of the weld, and if you can mow off the top 50% of the weld bead then the smut goes away. Also, when acet bottles are going "dry" the dirt accumulates at the bottoms. Since the bottles are not washed out, that I know of, during their very long lives, any impurities gather in the acetone over thousands of refillings, acetone being the vehicle which absorbs the acet gas within the bottle. As the bottle discharges the acetone remains and the energy in the remaining gas diminishes, and you end up adjusting the torch to compensate for lost heat and having a torch flame that is 3X as long as normally needed, and at the end the flame is large and "cold" - and sometimes schmutzig. sigh. Again, nice to see such sauber Verarbeitung.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#9
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Thank you for your nette Worte. Or better: Danke für die Blumen.
By the way...do you always have to coat the bottom of the sheet with flux? On a flange weld for examble, could you leave the 'touching' sides uncoated? Or welding on a bung...do you need flux between the bung and the sheet?
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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!) |
#10
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Quote:
This weld is very "smutty" - the term used by the Aluminum Association to describe carbon embedded in the surface of an aluminum weld.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
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