I have been struggling with getting my tack welds to be consistent. It goes from not enough tack to hold it to blow thru. I have read a bunch, but the advice seems to be all over. Some say tight, tight seams, others swear by gaps. I under stand the process of skipping around, but I don't get how to start the weld, getting both pieces without burning thru. running a 110v mig, 0.023 wire with argon/CO2 gas ~ 20 to 25 CFM. this isn't my pic below, just what I am trying to learn. Thanks for your help!
practice a lot on scrap metal, try different gaps, try different power and feed settings, see what happens, keep working until you get good at it. MIG butt welding sheet metal is challenging....you have to get the piece to fit just right, and have some skill at it.
As counter intuitive as it may seem blow through is usually a result of your wire speed being too slow. You are not pushing enough wire to fill what is being heated up. As squirrel mentions practice and playing around with your settings is about the only thing you can do to get better. The other thing you have to take into consideration is if you are trying to weld to old metal it may be thinner than the new metal due to corrosion which makes it even harder to do because the heat will burn away the old thin stuff before it heats up the new enough for good penetration. Make sure you take repairs back far enough that you are getting to good solid metal to work with.
I'm going to guess most of your problem is stemming from not "seeing the puddle". Seeing the puddle actually means being able to read the molten metal and watching the fusion of both pieces with the puddle. This takes nothing more than practice and then "BOOM" your eyes and brain recognize it just like that. Once the brain recognizes it the the " hand eye" coordination can begin. Gap or tight joint means you need to vary your technique and machine settings. With a gap, you need to build a bridge of molten metal. Faster wire speed adds cold metal to the molten puddle faster making it freeze faster. Faster than it can fall out. With a tight joint, you need to get the penetration thru the steel with the scrubbing and digging action of the arc and the puddle. What gauge metal are you patching with and is the cars original full thickness or thinned from rust? If its too thin, you're going to catch hell no matter what you do.
Copper behind the weld is a good idea, but if you don't have any handy, you can use a thick piece of steel also. If my machine is set up to weld thin stuff, then a 3/8 plate behind it won't stick, and will serve as a backer. I've used 1/4, and I've used 1/2 inch, too, and it only marks up the metal, it won't weld it together
MIG welding is somewhat abnormal to me, I used to Heliarch aluminum bodywork and found it to be a lot of fun. There is no control to MIG as I see it, and I've NEVER seen a puddle MIG welding, or trying to anyway. I did master the Orange County Choppers tac with your eyes closed method, and that is all done by sould. Sick welding, gas, and Heliarc/TIG all share a common puddle. MIG, I wish you luck, and invest heavily in gringing disks. Bob
I have a couple different copper items. 1" copper pipe pounded flat as well as one of those "copper" welling paddles. it has helped, but it still seems I am having more issues than I should.
Im no expert but I do have a couple mig welders. Sounds like you gas flow might be set a tad high. Only time I crank mine up like that is when Im outside in a breeze.
Yup. And the other thing I learned with MIG is don't hold the gun vertical, tilt it to 30 degrees from horizontal -- you won't blow through.
Those welds look tall, shorter burst or less wire feed depends on your method. I only run 7-8 cm on the gas when welding sheetmetal. Torch angle is critical, 30 degree suggestion above is a good one. From the piled up weld it doesn't look like you're moving the torch at all, you need to drag across the joint perpendicular to the seam, it bridges the gap and moves the heat zone. If you run into large gaps you can use thin round rod layed in the seam as a bridge filler. You need to turn up the heat and drag the bead across the seam. I buy the rod at the hardware store so it's decent quality but the body man that showed me the trick used coat hangers. Your gaps look fine.
im a way better grinder than a welder, but indyjps has it right. angle of the tip really helps and moving across the joint will fill without the burnout. but you still have to be fairly quick on the trigger. get a couple of pieces of scrap and practice it does help.
You say you are using Co2? you should be using 75 % argon 25 % Co2. also I have found the 110 v units to be harder to use than 220 v. I personally prefer a tight butt joint & as said clip the ball off the end of the wire. Are you using a auto darkening shield? Also if possible get as much light on your work as you can and as said practice on scrap before working on your car.
Here is a thread by a metal master...I have learned a TON from Roger's posts at Tri5, metalmeet, and SPI... http://www.trifive.com/forums/showthread.php?t=9511
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