What procedure are you using ....gun or tig?

 

 

longer tacks

 

Tig. Couldn't see doing it any other way

 

What do u mean longer tack?

 

i think he means more heat and little more filler

 

Aluminum short cracks really bad. You may need more filler on your tacks. Also if you notice the center of your crater is really sunk in, you can slowly ease off the pedal and allow the puddle to cool evenly.
If you get in this habit early on, you'll avoid cracked welds too

 

Yeah I'm looking at your photo, you need more heat. hit it with a wire wheel. Put D-nature alcohol and use rag that wont leave threads every where. Actually to much filler metal
can cause a crack. Not enough penetration. You'll get it. Hey at least your not welding aluminum with water trapped inside another plate like I did last week. lol.
http://markwilliamhowell.blogspot.com

 

I was trying to let off the petal slowly and sometimes it still cracks. Sometimes it cracks only half way across or quater of the way across the tack. Seems like if I wash the puddle around a little and blend it into the rest of the metal it seems to help. On steel I put the amps to about double I would normally weld and floor the pedal real quick and works like a charm but aluminum seems alot different.

 

hum. I usually go hotter with aluminum tig tacks.

 

Mark do u weld with a transformer? How much amps would u use for this 1/8th. I'm using 175 +

 

Yeah man I've always set machine super hot and stomp for the tacks. Make sure everything is super clean. You don't want that much metal on such thin gauge tubing. when you get a crater crack at the end the weld is done it will crack all the way down (linear crack)

 

I mean every machine is different man. numbers really don't do it for me. it looks as though you need more heat.

 

Ok I will try running my tacks in hotter. Can u tack aluminum with a quick bump of the pedal?

 

You should use filler to tack.
The arc will eat off a corner most times if you don't have filler rod to get your puddle started.

 

Alright I'll give you an example hope this helps. Lincoln Power Tic on AC no pulse setting pure argon gas lense #7 cup 100%tungstan 1/8 aluminum setting for tacks around 150
get a little cleaning action then go all the way. I usually dab the filler twice on tacks. and release the pedal quickly. Hope that info helps some what.

 

Personally I would never tack thin aluminum with out filler metal

 

I know Jodie does it sometimes but I've only seen him do it on thin aluminum like 1/16. The reason it might look a little cold is I didn't want it bigger then my weld will be. I might have to get over that. Do I need to wait for the 2 puddles to join or is it ok to jab the filler in real quick while there are 2 puddles?

 

The tack shown looks to have lack of reinforcement. In other words thicken them up. Sometimes cracks can appear at the beginning of a seam using 5356, and you have to pack in the rod to prevent it. Same with tacks.

 

Ok I'll try beefing them up and ill report back with my findings. Thanks guys for replying so quick!!!

 

you need to brush the bits of blue paper towel off before you start welding. A solvent wipe is insufficient to clean aluminum for welding. Use a small stainless brush and brush off the oxide layer. 6xxx extrusions are the worst when it comes to brushing the oxide layer off. As you brush, you will feel the brush bite into the metal instead of just slide across. Once you know what to look for, you will be able to see the surface transition from unbrushed oxide, to brushed oxide, to brushed bare metal. You kinda have to brush the s**t out of it with 6xxx tubes. Try 10 seconds of brushing per side (four sides of tube) to start. Resist the urge to just hammer on it with a power brush, as that will just shove the oxide into the base metal. Brushing in the same direction helps a lot too. Keep your AC balance somewhere around 55% EN to start (around 6-ish on the dial for transformer machines), and move more toward a balanced arc if you still can't get the tack to wet out quickly.
Also, autogenous welds are impossible with 6xxx aluminum. I love 5356 myself, and usually when I get tacks breaking it's because I didn't get it enough penetration. Nearly all extrusions (tubes) are 6xxx, and there needs to be a certain amount of dilution of the base metal with silicon (4043) or magnesium (5356) to prevent the hot short cracking that 6xxx alloys are susceptible to.
When welding 3003, it tacks up just great with no filler, provided your fit up is snug.
You asked about waiting for the two puddles to join. Sometimes they will, but the surface tension is pretty strong, and mostly they will just pull further apart from each other. It's a real problem sometimes getting the arc to evenly heat both pieces when the fit up has even a sub-millimeter gap. I feel like a snake-charmer sometimes trying to get the arc to evenly heat both sides, so what I do is let the arc heat the side it wants to, let the puddle form, then stab the filler in there and use the filler as a thermal bridge to conduct the heat to the other side.
If your fitup is dead nuts snug, the puddle will bridge the (nonexistent) gap and the puddle will flow just fine, but mostly you have to deal with some amount of gap.

Read all you can on Alcotec's website http://www.alcotec.com/us/en/education/knowledge/qa/How-to-Avoid-Cracking-in-Aluminum-Alloys.cfm

 

Very well said Bebo.

 

I always brush by hand until all the lines go away and until its shiny metal. And I wipe first with a acetone. Othere wise u with be smereing the dirt in the metal right? I gave that a quick wipe down after I brushed it bc I was wiping other areas and the rag was still wet. I'm gona start using a washcloth bc it always tears up the shop towel so quick. I wipe down my filler every time to. Those are really nasty! And when I preheat I brush a little after that to. A pro told me to do that

 

Nice man! Way to go on finding the right settings! I new it could be done. But my machine maxes out at 230. I will give it a try on practice peices. I love doing it on steel. U gota floor it fast tho. On steel u can put ur finger on it almost right away after you speed tack it bc it does it so quick

 

Aluminum Too.

 

Dave is showing off that he can vaporize a whole engine block in ten seconds, he's right, amp for amp, inverters tack quicker. I doubt anything tacks quicker than about 500 amps he can generate instantaneously. I do autogenous tacks on 16 gauge with a 280 and with a 310 amp transformer machine. Hot aluminum is very weak, You need lots of tacks. They can be very small, you just need a lot of them. Splattering acetone al over concerns me, but Zapster uses a toothbrush sized stainless brush with acetone to float contaminants away as they are scratched loose.

I set as hot as the machine will go. If it takes a second, that's too long for a tack without filler. Puddle too fast to let heat dissipate, or aluminum to oxidize.

 

What's wrong with acetone?

 

It's flammable, and soaks through skin to dissolve your internal organs. Use nitrile gloves, avoid breathing fumes, (use outdoors or with ventilation).

 

How do you prep your aluminum to clean it? I should get in the habit putting gloves on. I not afraid to try new things!

 

Watch this video mate.
[video=youtube;W8DV7lN7k9U]https://www.youtube.com/watch?v=W8DV7lN7k9U[/video]