Aluminum tubes welding 1

[Ahmmed123]

Hi,

I have been asked to design a 40 ft aluminum tube with a max deflection of 0.5". after calculating the DL, and LL I end up with OD 8.5" with wall thickness 0.5". the problem is I've got to weld two tubes to get the 40 ft length. does aws D1.2 talks about AL tubes welding, and does anyone have a website to get D1.2. Does anyone recommand a better code or reference for welding procedure???

Also I'm using type C backing ring??!!!

Thank you

 

[metengr]

Does anyone recommand a better code or reference for welding procedure???

No. You also better understand what type of aluminum you are going to weld.

 

[Ahmmed123]

Al 6061, I've got so many other shapes welded using both MIG and TIG welder. Also, I already have a procedure but I just wanted to double check with the codes!!!

 

[MikeHalloran]

I'm pretty sure the extruder makes tubes longer than 40 feet, and steel beams much longer than that are stocked and shipped without much fuss.

Talk to your tube supplier before getting too deep in butt welding.


Mike Halloran
Pembroke Pines, FL, USA

 

[Ahmmed123]

I did talk to my suppliers, I was able to find one in PA could get it me 40 ft tube but ..... it was too expensive and thats why I'm trying to weld.

I've talked to a welding engineer. he told me I could do it by tack weld the tubes at 4 points opposite to each other then weld all around " using a MIG" I guess I'll try that first on shorter tubes and see how it will go !!

 

[MikeHalloran]

Now, you need to find a heat treater who can handle your 40 foot welded tube. ... and you'll need a steel shipping jig to get it there undistorted.

Did anyone mention that welding leaves aluminum very soft?



Mike Halloran
Pembroke Pines, FL, USA

 

[Ahmmed123]

yeah I know the Al doesn't turn red before it melt. I have put that in mind " don't let it go too hot"

 

[MintJulep]

What Mike meant is that 6061 is almost always supplied in the T6 temper.

When you weld the temper is lost, the aluminum is left in a much softer and WEAKER annealed condition.

Did your calculations consider that?

 

[Ahmmed123]

well yeah this is my biggest concern, and I'm having a big deflection because of heat. that's why I'm asking about a good procedure to get the welding correctly!!

 

[MintJulep]

I was able to find one in PA could get it me 40 ft tube but ..... it was too expensive and thats why I'm trying to weld.

So you are going to buy a whole bunch of short tubes, ruin many of them trying to work out the welding process, finally put a "good enough" welded part into service, wait for it to fail and ultimately get the 40 foot long one-piece.

Yeah, that sounds a lot cheaper.

 

[drawoh]

Ahmmed123,

Read carefully what MikeHalloran and MintJulep are saying. For aluminium 6061-T6, [σ]_y=40,000psi.

For aluminium 6061-0, which is what you get in places, after welding, [σ]_y=8,000psi.

Warping due to welding is another problem.

JHG

 

[kingnero]

It does have its advantages though: you can predict exactly where it will fail. Just don't blame the welder!

 

[Ahmmed123]

mint for 40 ft it cost $3735.49 for two 24 ft each will cost me $775 only. you need to learn that tubes with market standard size are CHEAPER !!!

drawoh: that's true but I'm having only 0.833 lb/in load on it. second if you check the welding strength and the fatigue it won't fail. also I've run an FEM analysis on it and it passed. my total stress at y was much less thatn the 8000 psi. but Thank you

kingnero: I won't blame anyone, our competitors have made it before and it didn't fail !!

still I'm going to test it on a very short one, and again on a little longer one and see the welding effect and if it has a linear relation and on the deflection. even if I bought 3 tubes 24 ft it much cheaper than cutting 40 ft!!

 

[MiketheEngineer]

Buy the 40 footers - MUCH EASIER and cheaper as others are trying to explain. I am sure there are many vendors who can supply that and they ship nicely on a 40' flat bed truck. OR you might be able to sleeve and mechanically fasten??

 

[Ahmmed123]

OK everyone. I have built the tube (weld it) and I have load it to the design limit and it was linear elastic, and it's behaving as expected. now it have been installed and it's working very good. no need to spent extra money to extrude the tube.

kingnero : no one get blamed, have you been blaming your welder for your incorrect designs lol