Penetration on Aluminum

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I'd like to think I'm putting down decent looking beads on aluminum. I'm not wandering too much and the rhythm looks pretty steady. The problem I'm having is the backside of the welds look really bad. Bend it and the weld cracks and splits right down the center. There are some sections that look OK and I recall those were spots where the keyhole was on the verge of getting out of control or near the end of the bead(and the coupon was pretty heat soaked). I played around with brushing the backside as well but didn't notice much difference. Material and setup is as follows...Miller Dynasty 200DXWP-17 air-cooled torch65 amps, 65% balance, 100hz1/16" 1.5% Lanthanated tungstenGas lens w/ #7 cup, 15CFH1.5" x 4" x 0.063" 6061 Al coupons3/32" ER4043~1/16" root gap**quick note: A, and C were the first 2 beads and done with 1/16" ER4043. I switched to 3/32" after those because I felt the amount of rod I was feeding in was hard to do consistently(more apparent on A)Click to enlargeBackside
Reply:If it were me I would turn your balance to 80 and run no gap. Punch the pedal and drive the bead thru the joint.I think your choice to go to 3/32 rod is a good one.Good Luck!Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Hello derilious, your question has a number of different implications due to the fact that you are talking about aluminum. Unlike many other materials, aluminum has the nasty characteristic of instantly re-oxidizing when you stop cleaning it, apply heat and that accelerates the process. Another issue is the cleaning action of the arc itself, the reverse polarity side of the AC current is the part that does the surface cleaning. Since the backside of an aluminum open-root weld joint is not readily exposed to the action of the arc it is rather challenging to have the backside penetration ever match the torch side with the same degree of cleanliness or weld toe tie-in characteristics. When you are able to key-hole the joint and properly orient the torch angle-wise you will sometimes manage to make a clean tie-in/penetration. Takes a fair amount of practice and experimentation.      Another issue with welding aluminum in general has to do with it's as-welded strength. Unlike many other materials that don't change in their strength due to welding, aluminum can lose up to 30% of it's original tensile strength. Heat-treated grades of aluminum can become very challenging to weld on due to the loss of as-welded strength and the lack of readily being able to be reheat-treated. Even the heat-treating process is much different from the materials that most of have a concept for, such as steels for example. Many of the filler material grades used for welding aluminum are not able to be heat-treated, so a lot of the time the engineer or designer of the welded aluminum part has to approach it's design in a manner that allows for this reduction in strength. There is certainly more that can be said with regard to your questions. Others can likely shed additional and more specific information. Best of luck and regards, Allanaevald
Reply:I saw an article or post a long time ago where someone did a good test with photos showing  aluminum welds with and without a backer bar. I cant find it. I would like to see something like that done agin. Maybe i will in the future. It looks like some a couple little spots you welded came out nice on the back.www.performancealuminumfabrication.com
Reply:I found an interesting read here http://www.mig-welding.co.uk/aluminium-welding.htm. While it's really meant as MIG advice the first parts about brushing and oxide removal has some tips I'll try when I can get more aluminum to cut into coupons.
Reply:Originally Posted by travisc454I saw an article or post a long time ago where someone did a good test with photos showing  aluminum welds with and without a backer bar. I cant find it. I would like to see something like that done agin. Maybe i will in the future. It looks like some a couple little spots you welded came out nice on the back.
Reply:"buttcheeks"    No pictures, but you answered your own question.   Welding is like painting enamel. Put it on as thick (hot) as you can and keep controlAluminum takes time to read,   One way I can tell is if I add the filler in the front of the puddle it sucks it to the back.I think its double important to get the heat right DC +.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by hotrodderThis one (no backer bar though as that's cheating )? http://weldingweb.com/vbb/showthread.php?t=18625There were a couple of other threads started around the same time, this one has failures and successes both with and without backers... http://weldingweb.com/vbb/showthread.php?t=18542&highlight=penetration+alumi  num
Reply:I've had instances were I don't brush the aluminum and still get a clean puddle, other times it blobs up all together. To minimize the amount of material i have to scrap, I brush until I start to feel it drag a bit. That way I know there's at least one point that's clean and will start a nice arc.Still, I was impressed how he did everything "wrong" and still made a full pen weld even though the top looks odd.
Reply:Just a point. Aluminum work hardens rapidly and some of the strength that's lost to a fresh weld will come back with the work hardening.  That can probably only be counted on when welding with the same alloy. I worked for a company once that sheered all their own rod out of the stock that we were building things from.  It had to be anodized and that was the closest way to get the same color. And even then every weld showed up >  Mac
Reply:I almost never wire brush. And i like to think my welds turn out decent. But check this forum out. This is some humbling stuff. If you wanna get put in your place check this out. http://honda-tech.com/showthread.php?t=2503416&page=73 Its crazy because there are more bada$$ welders on a honda forum than on here. I would love to pick some of these guys brains. I wish they would visit us and give us some of their methods/secrets. They probably don't because anyone who tries to explain how they do something different (which they are obviously doing some things different) they get shat on by the weld police. BTW almost all the BADA$$ aluminum welds in there don't have a wire brush scratch on them. Just sayin. www.performancealuminumfabrication.com
Reply:I'm not a member there but I do have that thread bookmarked lol
Reply:Originally Posted by derilious...Still, I was impressed how he did everything "wrong" and still made a full pen weld even though the top looks odd.
Reply:Aluminum welding pornAll of his workhttp://www.yellowbullet.com/forum/sh...d.php?t=127750
Reply:Someone says aluminum and Marcella's name is sure to pop-up soon enough haha! His work is absolutely amazing! I'm burning up filler rod hoping to get half as good as him. It's so consistent, minimal etch zone, the man has to be half machine!
Reply:I talked with Him a while back on the phone to see what welder he has......Turns out he has a Miller  350 inverter  machine.......Since I use different gases to weld with I asked what gas he uses............Said he blends his own gas and it was a secret......LOL  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:It has been my experience that without some sort of "GAP" weld prep 100% pen is not going to happen with the correct amps for the thickness required to do a nice looking weld.....  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:That manifold is gorgeous!Buy American, or don't whine when you end up on the bread line.