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Thu Mar 08, 2007 5:51 am

I'm doing some body work on my beetle w/ a Miller 175, using .025 wire and co2/argon mix for gas. I use a wire wheel to clean up both pieces of metal and usually butt weld. I'm having problems with getting a decent bead, often the weld will spout up like lava in spots and blow off some trapped gas or impurities. This leaves pitts and holes in the bead. I run my gas at "20-30" trying to solve this problem, to no avail. Have tried going up and down w/ wire speed and voltage. It's hard to get that nice consistent "sizzle" going. Usually it's a sizzle, pop, then a ball forms on the end of my wire feed, or I blow a small hole thru the body :( Any thoughts or ideas? Maybe better metal prep? I take it down to bare metal.

Thu Mar 08, 2007 6:47 am

All i can offer is: The metal should be nice and clean, you should have a nice clean ground and a nice clean bare metal spot for the gound to attach to and make sure that the end of the welding gun is close to the surface you are welding so the gas will affect he weld-if the gun is too far away the gas will not have any effect.

Thu Mar 08, 2007 9:03 am

I am not a body guru but I have done my share of welding. Here goes:

Make sure your metal is as clean as humanly possible, I use a wire wheel and do not touch it with my hands after it is cleaned. Also what kind of steel is it? I have found that cheap metal ( china, canada, brasil, india) has alot of impurities in it that you cannot see on the outside, Canadian being the worst I have ever welded. Try a lower feed speed and amps, remember welding is not a race to the finish. As long as you get good penetration it is a good weld. And check that you still have gas, other than contamination in the metal itself the bubbling is also caused by oxidation in the pool itself aka Oxygen, the CO2 and Argon are to keep the O2 out of the pool. Even a tank with low pressure (500psi) will give you bubbling.
Try it and let us know

Thu Mar 08, 2007 10:01 am

little volcano's are usually from
contamation , microscopic rust
will cause this

Thu Mar 08, 2007 10:02 am

Saggs wrote: I'm doing some body work on my beetle w/ a Miller 175, using .025 wire and co2/argon mix for gas. I use a wire wheel to clean up both pieces of metal and usually butt weld. I'm having problems with getting a decent bead, often the weld will spout up like lava in spots and blow off some trapped gas or impurities. This leaves pitts and holes in the bead. I run my gas at "20-30" trying to solve this problem, to no avail. Have tried going up and down w/ wire speed and voltage. It's hard to get that nice consistent "sizzle" going. Usually it's a sizzle, pop, then a ball forms on the end of my wire feed, or I blow a small hole thru the body :( Any thoughts or ideas? Maybe better metal prep? I take it down to bare metal.
:?: Is it possible that this could be caused by oil or grease on the metal surface?

Here is a good reference on MIG Welding that was linked in another thread.

Thu Mar 08, 2007 7:10 pm

Absolutly, that is why I clean the metal and do not touch it with my bare hands. 2 reasons :it is hot, and I do not want to transfer oils or anything else I have on my hands to the bare metal. I use vice grips or pliers to hold it if small or just clamp it to a vice and wire wheel it there handeling it with pliers then.

Thu Mar 08, 2007 8:42 pm

I have the same welder. Sand blast the metal on both sides if you can and use pure argon, you should get better results.

Thu Mar 08, 2007 9:57 pm

Saggs wrote: I'm doing some body work on my beetle w/ a Miller 175, using .025 wire and co2/argon mix for gas. I use a wire wheel to clean up both pieces of metal and usually butt weld. I'm having problems with getting a decent bead, often the weld will spout up like lava in spots and blow off some trapped gas or impurities. This leaves pitts and holes in the bead. I run my gas at "20-30" trying to solve this problem, to no avail. Have tried going up and down w/ wire speed and voltage. It's hard to get that nice consistent "sizzle" going. Usually it's a sizzle, pop, then a ball forms on the end of my wire feed, or I blow a small hole thru the body :( Any thoughts or ideas? Maybe better metal prep? I take it down to bare metal.

OK. Let's cover the basics first. Make sure the area where your ground clamp is fastened is clean and your ground is clamped or screwed down tight. Make sure your gas is turned on (opened all the way up and gas coming out of the diffuser) You should be able to feel it on your face if you hold the gun close and squeeze the trigger. DO NOT STAB YOURSELF WITH THE WIRE!! :D Make sure there are no fans blowing or breezes coming in the door and keep your nozzle about 1/2" to 3/4" away from the surface MAX. The surface should be clean of rust, paint, dirt and oil etc. Post a pic.

Thu Mar 08, 2007 10:00 pm

A ball forming on the end of your wire could be a kink in your whip, wire feeder rols adjusted too incorrectly, or heat too settings off. Adjust one parameter at a time. If it gets better, adjust it until it doesn't get better, then adjust something else. Practice, a lot!!

Good luck.

Fri Mar 09, 2007 2:11 am

I am not sure what happened to my last message, maybe I pressed the wrong button but anyway. Too much gas flow is bad, as it causes turbulence that lets oxygen get into the weld, and encourages the weld to blow through or otherwise make a mess.

Make sure you are keeping a consistent distance (a few mm) between the gun and the work, and that you are 'pushing' the weld along (if you are using solid wire), with the gun at about 80 degree angle from the metal, and keeping a nice consistent speed.

Also, make sure your mig nozzle is clean! Even a small bit of crud in there can upset the gas flow. Good luck. If it doesn't work out, maybe post a picture or vid of how you hold/move the gun.

Fri Mar 09, 2007 5:54 am

Thx for the advice from all :) I'm sure I need to practice better cleaning procedures w/ the metal. I have usually been "building" my beads along off the hot metal behind my tip and "pulling" the bead along. Should I be "pushing" the bead along with my tip "leaned" back over the previous weld material? I have found that when welding thinner old metal I need to keep my weld hot and work along off that residual heat but not long enough to warp anything. I am using a heavy duty ground clamp on a clean sandblasted spot on my front qtr which is about a foot and a half from where I was welding. This should'nt be too far away should it? Another question: When butt welding how much gap should you have between panels and is the gap important? By the way, my welding tip is usually 1/4" or so from material-almost seems too close :?

Fri Mar 09, 2007 6:03 am

I've never been too obsessive about clean metal when welding. You can burn away a small amount of impurities. As mentioned by tchaika, check your nozzle for spatter build up. If you can't hear gas coming out when you press the trigger, that is probably the problem. No gap is required when welding thin materials. Do not run a continuos bead on thin material. This might help:

http://metalshapers.org/101/jkelly/index.html

John www.ghiaspecialties.com

Fri Mar 09, 2007 6:49 am

A foot and a half sounds fine, it is really people doing silly things like earthing to the other side of the car, their brake disc, the door, another panel only connected by a few spot welds, etc - common sense, the electricity has to complete the circuit back to the welder.
Yes, you should be 'pushing' the weld along as you describe, i.e. the weld is made and then goes under your hands, instead of 'pulling' it along (your hands are over the unwelded metal the whole time). This is necessary so that the gas can shield the weld as it is designed to. With flux core wire, you do the opposite, since you do not have the gas shielding issue. Try holding the torch just off vertical, i.e. 80 degrees up from the metal.
I'd bet a dollar this is the cause of your porosity.

Get yourself comfortable in a position where you can see the weld building up underneath the torch (but watch out for sparks).

Gap, different people have different preferences, from none to 1-2mm. I am not a mig sheet metal expert but I think a smaller gap is better, as it requires putting less mig wire in, which is usually really hard to hammer/dolly afterwards, and prevents putting more in heat from grinding (risk of warping). Also I feel that a closer gap is indicative of more effort put into making a nicely fitting patch.

If your heat and wire speed are about right, your weld should sound kindof like popcorn popping on a hot stove. But some kind of weird popcorn made of metal, if that makes sense. If the sound is more dull, fizzing, ticking, dripping than popping or snapping, it's not quite right.

MIG is more 'resistant' to impurities than some other welding methods, but lack of cleanliness can come back to haunt you as rust that starts from your weld (or, if it's really bad, cracks). It's a shame to go to all that effort and not spend a minute or two more getting to shiny metal. It does not need to be clean enough to eat off, but no paint, rust, or oil/grease/water/etc.

Test your welds before you start work on a car. Try cutting across the weld to see what it looks like inside, and bending the weld back and forth to see how easily it breaks. Post some pics if you want feedback, there are a lot of variables when you are getting started..

Sat Mar 10, 2007 12:58 am

I agree with those saying you're not getting the shielding gas out of the torch. When my tank has ran out of gas, or when I've accidentally not turned it on, I get the exact symptoms you are describing.

Scott Faivre

Sat Mar 10, 2007 3:25 pm

Use a bucket of clean water and submerge your welding tip to check for gas flow. works better than your face as suggested earlier.

Sun Mar 11, 2007 10:50 am

I have the same mig welder, wire, and shielding gas as you do and on mine, I not only clean the nozzle, I check the four little holes near the end of the gun, just below the tip. Occasionally, one or two of the holes have been plugged up with junk, probably from the gel that I spray on the nozzle. Once, some of the holes were so plugged up that not enough shielding gas was coming out and the result was a weld like you had.

Mon Mar 12, 2007 8:34 pm

I had te same problem yesterday both pieces were sand blasted, I had cut back 2 inches away frm the rot. I then cut out some of the body above the weld and it was still rusty.I ended up bending the body panel at a slight angle to make a thin flange about 1/16 inch It worked as it would have been to hard to get behind it to sandblast.