Aluminum Weld Failure

admin

Seeking advice;Sometimes I have problems getting my aluminum welds to hold. Other times they are fine. Today I spent the usual time cleaning the aluminum and attempted to weld a couple of 1/8" thick 1" square tubing. I could tell during the weld that it wasn't a "good" weld. After I finished the weld I put some pressure on it and the weld broke, very weak. I can't seem to understand exactly what is wrong. Some of my other welds hold fine. Please take a look and give me your opinion if you have experince with aluminum welding.My Machine:Miller 212 with a 30A Spoolgun using 5036 - .030 WireI have the power on 6.5 and the wire speed on 6 (spoolgun).Thanks Attached Images
Reply:Okay, FWIW, the weld was crap. ZERO penetration. And, to make matters worse, you ground/ sanded the weld. That's kind of a widely known Now, onto WHY.......I saw the pic of the welder, but there are some variables. I am sure you do get a good weld, then a bad one if the technique is not correct from one to the other. When the material is set up, do you preheat at all? (5-10 seconds with a mapp or propane torch on the joint will make an AMAZING difference, especially for a mig with no hot start feature.)Stick-out makes a huge difference. Shielding gas is critical for alum. mig, and the stick out will lose a lot of heat in the weld the further you run the stick out. Also, a longer stick will leave the wire flimsy, and you can't 'push' the weld puddle into the materials. Your weld was biting down on the bottom, but you did not center it up to have it penetrate the sq. tube at all. Angle of the spool gun is critical for this. Gotta get the molten puddle on BOTH pieces of material or it is a moot point. No prep for the part; the sq. tube had zero bevel on it. While you CAN get a good weld running a piece with little prep work, you must realize you need to have enough heat to fully dig into that sq. tubing. And, you need a weld bead that has a cross section of the thickness of the thicker material. So say you are welding a 1/8" sq. tube to a 3/16" plate. You want/ NEED a full 3/16" weld bead to get the same strength across the weld as the material. Anything less, and you are looking at a guaranteed weak weld.Heat; I just looked back at your pic; aluminum takes a boat load more heat than steel due to it's thermal conductivity. It sucks up heat and spreads it rapidly. Crank that dial up to almost double what your thickness gauge is. You look to be running for 1/8"..... set it more toward the high side of 3/16, low side of 1/4" and see how that helps!I hope these will help you out a bit.  Don't feel bad, mig aluminum is always a tough game.Last edited by Rojodiablo; 08-15-2011 at 02:10 AM.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Originally Posted by KaosMy Machine:Miller 212 with a 30A Spoolgun using 5036 - .030 WireI have the power on 6.5 and the wire speed on 6 (spoolgun).
Reply:Rojodiablo,Thanks for your help!DSW,I looked at the suggested settings but I must have misread, I thought it said 6.5 / 6.Thanks!Last edited by Kaos; 08-15-2011 at 09:12 AM.
Reply:Originally Posted by DSWDid you look at the suggested settings on that cover? The manual shows that for the 30A Spoolgun using 5036 - .030 Wire for 1/8" alum you should be set at 6.5 on volts and 8.5 on the wire. If you set it hotter for 3/16" as Ed suggested, you should be on 7.5 on the volts and MAX on the wire.Your slow wire speed is probably a big part of why you don't have good penetration. On the same voltage, faster wire speed equals more amps. Stickout may also be an issue as Ed suggested. I find a lot of guys I help teach like to run very long stickout with mig and they have issues because of it. Alum mig is fast and hot. Alum mig can be a real PITA with welds that short. You are almost finished as soon as you pull the trigger.
Reply:Sorry Rojo, I wasn't awake yet  this morning....No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan