MIG Welding

The welding class is now in full swing, with plenty of time to weld.
Of all the welding processed that we tried, we are now on GMAW. I had
full two hours to practice. The welding machine was a digital Lincoln MIG welder the size of a Millermatic 250.
I was pleasantly surprised how it lets me make nice looking welds (relatively speaking) without too much practice.
I set the machine in full accordance with the diagram.
Then I tried making a inside corner weld, which looked fairly decent, using 1/4" plates and (IIRC) 320 IPM of 0.035 at 19v.
Then, recalling Gunner's infamous tire holder incident, I took it to a anvil and pounded on this weldment, trying to flatten it.
To my disappointment, this solid looking weld failed in several places, obviously revealing no fusion at all in those places. The assembly held because in other places, the weld did not fail,but it was not what I would call an encouraging experience.
I am not complaining, as such, the instructor told me that I should have chosen different settings, etc and I am sure that he is right. But, I think, given my low skill etc, I would not trust MIG with anything critical.
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I've had the same experience. With my tired old eyes and the fact that I weld only very occasionally, I select stick 6011 for anything needing strength. No way you won't have penetration with this rod. I use mig where the stick is going to burn through.
Karl
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Thanks to SteveB, I use 7018 almost exclusively...
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Karl Townsend wrote:

My sentiments exactly. I am too often amazed at beautiful MIG welds that have NO penetration on one side. Makes me nervous about the consequences of failure.
I use 6013 - it's basically a contact rod so that my loss of touch from infrequent use is not a problem. I have 6010 (more like 6011, I think), but it sticks enough to be too frustrating and I very seldom use it. 7018 may be a great rod, but it can't be enough better than 6013 to be worth needing an oven to keep it dry.
Bob
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Ignoramus21227 wrote:

I find that the tables glued to the inside door of the machine are often for butt joints in flat plate, I usually set up as if I'm welding about 50% thicker material than what I'm actually using. This lets corners weld really nicely. When subjected to destructive testing the steel tube tears out well before the weld fails.
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Wire welding is used extensively in joining fabricated pieces for a wide variety of highway-use implements.. trailer hitch receivers, trailers, etc.
For any utility welding (not art), forget about weld appearance, as in the expression: chrome won't get you home. The second habit of mine is not to rush the welding. Taking the time to know that the proper penetration is taking place, will always produce stronger welds, IMO.
I have used flux core wire for the last several years, and the only weak welds that I've experienced were welds that had full penetration, but pulled out completely, because the material was OBF (old bed frame) angle iron. That part was remade from new mill steel, even though it was just a mount for a fractional HP electric motor.
I'm not a certified weldor, more like a certified futzor.
The last highway-use item I fabricated and finished was a hitch-type receiver at the back of a camper trailer, for a bicycle rack. From the receiver tube, the commercially-made rack extends several inches horizontally, then several feet vertically, then about a foot vertically again, forming the perch where 2 medium weight bicycles mount.
The owner traveled from western PA to CO, NM, AZ etc. on a month-long trip last year, and then numerous other shorter trips since then.
The welder is a 5-6 year old (purchased new) Hobart 135 120VAC model. I wouldn't find it practical to weld 1" steel with a 120VAC machine, although Ernie L has done it, but he's been a welding instructor and professional weldor for a long time.
I'll probably get a higher current model when I locate a place with a decent sized shop area, but using a quality 120VAC machine isn't as miserable as some folks might think.
WB ......... metalworking projects www.kwagmire.com/metal_proj.html

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Curt, everything that I have seen so far suggests that flux core is a lot hotter and always guarantees fusion. (none of this is based on any personal experience). Possibly, the way to go for me, if I want to expand my own welding, would be to use my LN-25 wirefeed (which so far has not seen any use) with fluxcore.
i
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Curt who, Ig? heh
I believe I've read that using CO2 with steel wire is hotter, from numerous sources, but I haven't tried it myself.
AFAIK, there are no "always guarantees" (about nearly anything).
WB ......... metalworking projects www.kwagmire.com/metal_proj.html
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On Fri, 17 Oct 2008 13:26:19 -0400, "Wild_Bill"

Straight CO2 is suppose to give you a bit more penetration, but you'll get more splatter than say with a mix. It should be cheaper than the mixtures too.
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Leon Fisk
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I've seen and have tried anti-splatter sprays, but I suspect that if the fluid gets into the weld zone, that it most likely has an effect on the quality of the weld, but maybe not.
It seems to me, anyway, that anything other than filler metal in the weld would be a detrimental contaminant.
One could cover the seam/weld zone with masking tape and then remove the tape after spraying, but that kinda defeats the instantaneous push button solution/miracle that most folks expect from an areosol product.
I ended up using the anti-splatter product that I had as a corrosion inhibitor on my steel stock, since it seemed to feel like a parrafin-type residue.
WB ......... metalworking projects www.kwagmire.com/metal_proj.html
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wrote:

In my experience, straight CO2 runs colder than mix.
Steve
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On Fri, 17 Oct 2008 14:23:00 -0400, Leon Fisk

It gives a LOT more penetration and significantly more spatter. An antispatter spray such as PAM cooking spray etc are de rigor for anything you want to be pretty.
Gunner
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I was starting to wonder of there was another Curt here! :)

Mig is not all that hard to learn to do right. But for thicker structural stuff like you tried, you really do have to test it like you did as you are learning to find out what works and what doesn't work. It was a real eye opener for me when I started to do bend tests on the MIG welds.
You have to keep the wire contacting the leading edge of the weld pool. A big mistake is to let the weld pool spill out in front of the weld as you are adding the wire to the top of the pool. The heat is being added at the point the wire is contacting the weld pool, and when you add it to the top, and let the edge spill out over the metal, the leading edge gets too cool and just cold laps onto the metal instead of melting it. So keep the contact point of the wire, and the heat, as near to to base metal as possible to make sure you are getting enough heat there to melt the base metal. The more you do it, the more you will be able to recognize when the base metal is correctly melting instead of cold lapping.
When doing a fillet weld, it's far too easy to end up with it contacting and melting one side of the weld while cold-lapping the other. I like to use a circular pattern or weave (depending on position size, etc) to make sure the weld is melting into both sides. If you do a straight stringer pass on a fillet, the odds are one side will weld and the other will cold lap on you.
The other fun thing to do is crank up the voltage and wire speed to get it into spray transfer mode (assuming you are on a machine large enough to do that - my little 220 V machine can't do it). It just slices through the metal allowing for huge amounts of penetration. You don't have cold lap problems in spray transfer mode. When stick welding 3/8" steel in a T (fillet) with 1/8" 6010 or 7018 it took some practice to make the weld actually penetrate past the point where the two pieces came together. It's hard to get even 1/8" penetration there. But with MIG in spray transfer mode, I was getting penetration on the order of 1/4" deep without even trying.
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Curt Welch http://CurtWelch.Com /
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Did your spray warp your plate? I like pulse because I can weld for long times without warping the joints, but your point about where to aim the wire was dead on. If you aren't pushing the leading edge of the puddle forward along the joint, you won't get fusion.
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Tin Lizzie
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I don't remember it warping, but it was just a 8" test coupon not something I cared about. I probably didn't even look to see how much it warped. I would expect it to be a real problem on some work however simply because it does put so much heat into the weld.
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Trade that LN-25 in for a LN-15, get a Lincoln 350 power supply, and link them with a "brain" cable. Learn parameters for pulse, keep a cheat sheet in the LN-15 box, and use 95/5 argon/CO2 mix. You can weld just about anything with little to no distortion. (still need pre-heat on thick stuff, tho...)
I've run both the LN-15 and LN-25. The 25 is a piece of !&^%. I've run very little spray, lots more pulse, and we have different machines for dual-shield.
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Can you tell me what exactly you did not like in a LN-25?
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The LN-25 would run straight off of 440v 30a 3 phase power, making it easier for us to move around in the yard, but it lacks the programmable settings and extra features that are available on the Lincoln V350 power source connected to a LN-15 feeder (power and "brain" cable connections). Those extra settings make pulsing a breeze, and virtually eliminated our ultrasound test (UT) failures.
I have a manual at work, but I'm sure you could do a comparison online at the Lincoln website. FWIW, I haven't run a LN-25 in over a year, maybe they have a newer, improved model out now.
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My LN-25 is a suitcase wirefeed that can work with CC welders, getting power from across the arc.
i

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wrote:

I've used an elcheapo flux core 120VAC welder for years. Two heat settings and variable wire speed. I just go slow and match it melt in on both sides as I go and I have welded material upto 1/4" with good results. The biggest problem for me is the very limited duty cycle. I have fabricated trailer hitches on trailers, satellite mounts, gate handles, and a variety of other things with it. I found pretty much universally if my welds looked good with it, they were good. (with steel).
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