[DougW]

Hmmmmm.... Practice is done and time to get started on project.

I've got 2 - 80" x 1.75" sq. tubing - .125" wall

I've got 3 crossmembers 8.5" x 1.75" tubing - .125" wall

I am trying to do some simple fusion tacks. Have done 100's if not 1,000's of them practicing these last few months - without issue.

Now virtually all my tacks are cracking. I would guess 8 of 12 have problems. Soooo... picked up some 5356 and laid down a small stitch weld. It cracked too. The only difference I've got is mass. The pieces are bigger. The only solution I can come up with is to pre-heat each joint until such a time as welding puts enough heat in the parts/pieces. What say the masses?

Settings 180amp, 125-F, 65 EN, gas ~13 CFH, 3/16" purple tungsten, #5 alumina ceramic cup

[Oscar]

I have a feeling it's the shape. Please post a close-up picture of said tacks.

3/16" purple tungsten

I think you mean 3/32". Even I don't have 3/16" tungsten!

[DougW]

3/32... 3/16... details... details... details..... OK... let's go with 3/32!

This one is dirty, now. It wasn't but then I went back on it with filler rod 5353 to try to "heal" it...

20200614_103305 by Doug Wei, on Flickr

Basically the same thing. Original fusion tack cracked... tried going back with 1/16" filler. I'm kinna free handing this stuff cause I've got the pieces clamped down to a piece of MFD. Soooo... gimme'a break on the uglies...

20200614_103227 by Doug Wei, on Flickr

[cj737]

Ally doesn't "fuse tack" well. It can be done, but it is not suggested unless the joint has an overlap. Also, post flow time is critical for avoiding cracking with tacks. Set yours to 8-10 seconds, and use a dab of filler (even 1/16") will help.

[DougW]

Ok... thanks I'll give it a try. My post flow had been 5 sec. and I wasn't really holding the torch over the tack even that long. So now post is set to 10sec. Gonna flip it over and tack the bottome side n' see what happens?

Any idea why I could hand hold/tack all the pieces I practiced on up until this point? I don't recall any of them cracking.

[DougW]

Ok... made the changes in post flow and added 1/16" 5356. It helped I still had 2 out of 8 tack/stitches crack but again that could'a been me moving the torch too soon.

Here's a look at what I'm working with...

20200614_111832 by Doug Wei, on Flickr

And tack/stitches after implementing recommended changes...

Some of the tacks ended up heavily oxidized but I'm not real sure why. I think it happens when I have trouble getting filler to the pool soon after it pools up. Maybe too hot?

20200614_111816 by Doug Wei, on Flickr

20200614_111811 by Doug Wei, on Flickr

Both of these cracked....

20200614_111759 by Doug Wei, on Flickr

I will confess to havin' issues with the filler rod/torch movement while leaning over this stuff. I'm hoping once I get rolling with the full welds I can kinna clean some of those "nasties" up....

20200614_111752 by Doug Wei, on Flickr

[DougW]

Welllll... ain't gonna win no 'pretty' awards but one side of the butt welds is done...

CJ's gonna tell me "Get it hotter!" but if he could see the full scope of what I'm building perhaps he's appreciate why I'm reluctant to get full penetration on these welds.

20200614_114703 by Doug Wei, on Flickr

20200614_114654 by Doug Wei, on Flickr

20200614_114647 by Doug Wei, on Flickr

20200614_114641 by Doug Wei, on Flickr

Yeah... I dipped the tungsten a few times...

20200614_114634 by Doug Wei, on Flickr

[Oscar]

Did you notice how the tacks that cracked have a deep concave shape? That bead shape easily propagates stress, sort of like an inside corner. The stress just from cooling back to room temp is enough to initiate that crack. Plump them up with a dab of filler, or two.

[cj737]

Make sure you study your pictures and understand Oscar’s point. When you finish an ally weld, it is really critical that you dint leave a crater in the last bead. Before you reach the end, begin tapering your heat, and add extra dabs. Even if they appear bulbous, that’s fine. You have to fill that crater because it will “hot short crack” and send that crack back along your weld every time.

For 1/8” wall, you don’t need full penetration. You can intentionally create a very small gap and weld that way. Have any MIG wire? If so, cut a short strand and space your pieces with it. Weld, jerk the wire out, and fill. I do it all the time especially with thick aluminum. As you get fully welded, the gap closes up due to heat and you’ll end with a butt joint by the end.

[DougW]

Knowin' what to do and being able to do it sometimes causes problems...

When you see the plum of black soot at the ends of my welds... I'm trying to reduce heat, circle the torch and add a few dabs right as the pool solidifies... Sometimes are better'n others...

But all the butt welds are done on to the fillet welds...

In person these really don't look too bad. The camera is kinda cruel sometimes. The craters at the end of the weld are very shallow and look little like they do in the photos... As you can probably tell I wire brushed some, if not all, of the following welds because at some point I "big dippered" them. But I suppose wire brushing is a cut above grinding!

20200614_141620 by Doug Wei, on Flickr

20200614_141612 by Doug Wei, on Flickr

Without everyone's help I would'n'ta' got this far and the help is truly appreciated!

[motox]

looks like a long arc weld.

[motox]

tighten up the arc on that joint. maybe longer stick out..

[DougW]

Not sure I understand all the terminology....

What I am doing is moving the arc from the vertical piece to the horizontal piece and dabbing as required. Are you saying focus the arc at the center of the joint and don't move up and down with the arc?

My pattern is kinna: up/down/back/dab.... up/down/back/dab... 'cept when I dab w/o backing up and poof...

Took me a month to figure out I'm not supposed to feed tungsten in the weld like wire on a mig welder!

I'm gonna.... get a little more stick out and put the arc in the center of the fillet and use the 'advance/retreat' pattern with the torch. And maybe bump the frequency from 125 to 150...

Thanks for the input!

[motox]

doug
check out this video
https://www.youtube.com/watch?time_cont ... =emb_title

[Oscar]

doug
check out this video
https://www.youtube.com/watch?time_cont ... =emb_title

That's one excellent video from Jody on aluminum, for sure.

Not sure I understand all the terminology....

By all means, ask away. It's the only way you'll learn.

What I am doing is moving the arc from the vertical piece to the horizontal piece and dabbing as required.

IMO, that's exactly what you should NOT do. It's not that it's incorrect in and of itself, but without proper technique, you end up creating a bridge, and not fusing into the root, creating a continual lack-of-fusion along the whole joint. Such is the case here. You typically don't want this.

Are you saying focus the arc at the center of the joint and don't move up and down with the arc?

Yes.

[DougW]

Thanks Oscar!

I'd watched that video before. Funny how as you gain a little bit of experience you hear and see things that didn't register before. I've only got 3-4 fillet welds left on my project. The last few I did I bumped the frequency to 180. The last weld Jody did in that video he had the frequency at 250! Soooo... guess I'll grind an electrode with a blunt angle and bump the frequency up some more n' see what happens!

[DougW]

Last two welds I tried to "tighten" em up... Without a doubt they are my worst two welds on the project. I upped the amps from 180 to 220 and the frequency from 150(I think) to 200. I tried those settings on a couple of scrap pieces and did get some full penetration which I simply can't have on this project. But... went with it anyhow. I suppose I was dipping the tungsten but it seemed like it was jumping from the weld to the electrode. I really don't know what was happening other'n it was pretty fugly. In the end they cleaned up to "ok". I haven't gotten brave enough to look in the inside of the tube to see if I got penetration exactly in the middle of an 80"piece - I hope not!

Thanks again for everyone's help!

[DougW]

Yes.

I recognize that weld!!!!

[v5cvbb]

doug
check out this video
https://www.youtube.com/watch?time_cont ... =emb_title

Thanks for the link. This is a video I had seen, but really needed to rewatch!

[VA-Sawyer]

What alloy of aluminum is the tubing?
That makes a big difference on the preferred filler, and how easy they will weld.

[DougW]

What alloy of aluminum is the tubing?
That makes a big difference on the preferred filler, and how easy they will weld.

The tubing is 6061. I practiced with 4043, 5356, and 4943. I liked the welding properties of the 5356. So that's what I used on this project. The reason I liked it is because of the 3 it was the slowest to wet-out/flow. Working with small practice pieces relative to the large project pieces the 5356 was a good match for the small hot practice pieces. With hind sight being 20/20 and all'a that, for my experience level and associated skill set the 4943 may have been the better choice... The quicker/easier wet out/flow of 4943 coupled with the need to not get full penetration makes it seem now like a no-brainer. The size of the project pieces vs the small size of my practice pieces had an negative impact as well. That wasn't totally unexpected. From practice to project I changed the electrode tip angle from ~15 degrees to ~60 degrees. I blunted the tip but I was doing that in practice as well. I did use the 15 degree non-blunted tip while I was tacking the pieces though.

But... It's all welded up. It ain't gonna fall apart. The welds, though not x-ray quality, look decent to me. Everything could be better and everything could be worse. Sooo... in the end the results were 'meh...' which I suppose is better than OMG!