[Otto Nobedder]

Here's the etch. The point I was making was breaking the edge of the leg on a Tee joint, and this shows it. I'm a bit disappointed in the penetration on the base, but it's sufficient.

Al Etch.jpg (35.25 KiB) Viewed 1025 times

Steve S

[exnailpounder]

Next to the leg of your tee..on both sides is a little flat spot before the obvious penetration...that's a little bridging and that's hard to avoid when doing thick to thin. I bet if you put some dye penetrant on it, it would show a tiny crack there. You had the same result I had which is when you taper the leg, it becomes a thicker to thinner scenario. I can see where on the right side you concentrated your heat more on the thicker piece...or the metal was just super hot when you welded it. You have to move out so as not to melt the thin leg at the expense of getting less penetration on the thicker piece. I do alot of thick to thin stuff on other metals and I always concentrate the heat on the thick piece and wash up onto the thinner piece but aluminum doesn't work like that. If you're using enough amps to melt 1/4" AL...then those same amps will flat melt out thinner material. I had to weld some .062 box tube AL to 3/16"...what a freaking nightmare...I did it but the thin metal is almost at critical mass before you hardly make a dent in the thicker stuff. There is alot more to welding aluminum than it just looks cool.

[exnailpounder]

20170430_110132.jpg (41.78 KiB) Viewed 999 times

This is a little blurry because my camera on my phone sux but you can really see the nugget on this one. I used Zep concentrated purple cleaner which has sodium hydroxide in it. Really etches good.

[Otto Nobedder]

Actually, Jeff, this was prepped square. I did not taper the leg of the tee. I was hoping to demonstrate penetrating into the corner for full depth on the weld, rather than bridging over it with filler. What I think happened was the "table", a slab of 1/2" aluminum, acted as a heat sink and limited my penetration into the base.

Yes, I noticed the little flat spot. In one I broke (I used an L-dog and wedge to dog down a big gap on a doubler, fillet on one side, broke off with hammer after) I noticed molten aluminum wicked into the joint beyond the penetration, giving a distinct appearance of a line of lack of fusion. I wish I'd photo'd that.

Storming like crazy here at the moment, lightning dancing all around. I live among the trees, so that always makes me a bit nervous.

Steve

[exnailpounder]

Actually, Jeff, this was prepped square. I did not taper the leg of the tee. I was hoping to demonstrate penetrating into the corner for full depth on the weld, rather than bridging over it with filler. What I think happened was the "table", a slab of 1/2" aluminum, acted as a heat sink and limited my penetration into the base.

Yes, I noticed the little flat spot. In one I broke (I used an L-dog and wedge to dog down a big gap on a doubler, fillet on one side, broke off with hammer after) I noticed molten aluminum wicked into the joint beyond the penetration, giving a distinct appearance of a line of lack of fusion. I wish I'd photo'd that.

Storming like crazy here at the moment, lightning dancing all around. I live among the trees, so that always makes me a bit nervous.

Steve

My second pic is the same as yours. I didn't taper either but it just hit me...if we did taper and this was our weld profile, we would have had almost no penetration into the leg of the T. But if you look at my first attempt, you can see very obvious lack of penetration on the bottom of the T on the tapered one and come to think of it...I welded on a big slab of 3/4" AL myself...wonder if that could have skewed anything? This cutting and etching sure is an eye opener. I don't weld AL very much but I will pay more attention from now on.

[Otto Nobedder]

Jeff, I'm stunned at the difference in penetration between the leg and the base, and since you said you used a slab of aluminum as your table as well, I really do have to wonder if the heat sink effect affected our penetration on the base.

Amazing the things we learn when we try to teach others...

Steve

[exnailpounder]

Jeff, I'm stunned at the difference in penetration between the leg and the base, and since you said you used a slab of aluminum as your table as well, I really do have to wonder if the heat sink effect affected our penetration on the base.

Amazing the things we learn when we try to teach others...

Steve

I use that thick slab of AL I have for a heat sink for SS so I would almost bet that using it for AL had some effect. And I also thought about this; it matters where you take your slice out because as you are welding towards the end of a piece, heat is building with no where to go and you have to start backing down the pedal so it matters penetration wise...also, I am guessing for a true test, the piece would have to be cooled or quenched between welds...all things being equal...Here's the biggest question yet...WTF was the point of all this in the first place I need a drink