120v MIG 3/8" coupon test results

[aczlan]

Aaron, not sure how you got those numbers but a 1/4-20 bolt is generally good for around 3,500 lbs in shear, or I typically use 4,000. And two of them would be good for (in general) twice that, or 7-8,000 lbs in shear. There are other details, probably more than you ever want to know, but just wanted to clarify your numbers are a ways off. Just FYI, I am a Mechanical Engineer, this subject is well within my skillset. I don't do engineering anymore except I build my own stuff and run some numbers sometimes.

I see that now. I mixed up inches in diameter with square inches, so I did 85,000 (shear strength per square inch)*0.25 instead of 85,000*0.049.

Aaron Z

 

[firemanmike69]

Hey FiremanMike, thanks for doing the tests and showing what the 120Vwelder could do. I think it was a good idea you had to do the same with a 220V welder and see what the results are. I have a feeling that there would be a lot of failures from average joe guys on those tests even with 220 V. Even more though, I am intersted in anything that you may have done to make the weld stronger and better than it might have been if someone less expereinced than you was to weld it. :thumbsup: Cheers bro.

To do things differently in the future I would have cut off the portions that were the beginning and end of the welds. I also would have rigged up a bender that was a bit more capable of bending the coupons in a gentile "U" shape instead of just folding them in half with my press

 

[Mark @ Everlast]

Ok so...
Been catching up on some back logged work...
The Background information:
I got an opportunity today to do a bonafide test. I will preface this by saying, I have had plenty of bend tests conducted on my work. I know how to weld up bend and have done many of them. I only had one MIG test plate fail...the first time I attempted 4G. Once I figured out what I did wrong, the next one passed easily. I have passed 1G 2G 3G, 4G with Stick, MIG and TIG, and 6G on 6" pipe with it in a fixed position with both 6010 root/7018 and TIG root with 7018 fill and pass.
I welded up a 6" long, 3/8" thick plate with a 37.5 degree bevel on each side with our 140E MIG with Techniweld .030" loaded in. I will be cutting from the center of the coupon two 1.5" coupons. I took my time, did it open root with a 3/32 land and 1/8" root gap. The welds looked beautiful on the surface, and being a little bit rusty myself since I haven't done a test plate in a while I took time to remove any silicone and did ground down any suspect areas. I looked close with my reading glasses (have had to start wearing them in the last year) while welding and the metal laid in smoothly. I ran 30 or more test beads on a piece of 1/4" plate finding the right balance of wire speed and volts. I actually felt like I needed more, but the unit was tripping my 20 amp slow trip breaker with volts about 50% and amps at about 65% of maximum adjustment after 5 or 6 inches of continuous welding...so I backed it down. I made a quick"rush" test plate to confirm my settings...not for testing but just to get the feel of the machine. It felt solid, but the puddle felt a little cold still. The machine is rated for 140 amps at 25% duty cycle and never hit it while welding nearly continuously...But it will pull a lot of amps on 120V. It will pull 38 amps inrush. So, obviously running it at less than maximum power, and well under what I was comfortable with but it seemed to lay in fairly nice...On the surface it appeared well fused at the toes and free of porosity. Here are a few photos of what was going on when I did the "Real" test plate. I snapped most of these out of the video I took. Looks good right? (Or at least decent for a first time real use and setup of the machine). First I made tack welds to maintain the 1/8" root gap, then ground the tack down. The next pic is the root pass and then the back side of the weld. Just about right, maybe a little over-reinforcement, but plenty of what appears to be penetration. No the last images are not from it being welded from the backside, but rather the way an open root weld looks from the back side.

 

[Mark @ Everlast]

Next up...one of the fill passes. Not the best I have made, so I ground it out until I felt comfortable with the fusion in the toes...and then laid two more filler passes on top of that, increasing the volts and wire speed to just under the trip mark as I felt it needed a little more umph...and each time cleaning up the toes so that no silicone slag was trapped there. Next you can see the first "Cap" pass. I made two. I definitely did not want to weave that wide .030" wire. But it looks good. Keep in mind that brown stuff got cleaned off before the next weld...so the next pass was always on shiny, fresh metal. You can see the thickness of the layer by observing the ridge line on the other side of the cap pass... I am not laying in a thick globby pass here...many people make a mistake of trying to weld it all in one pass and that is a recipe for failure. You can see the second cap pass which is the last weld. Looks good. One tiny area that concerned me, but it will likely be cut out any way. The last picture depicts the top of the weld after it is ground flush. No underfill, but there is something that is concerning me... a little crack...or line rather ...a tell, tale sign of possible trouble on the horizon.

 

[firemanmike69]

Looks like you put a bit more time in it thank I did,great looking plate I'm anxious to see it cut and bent

 

[MossRoad]

I guess I should try to figure out what constitutes "pokes". I pretty much have to go on what they wrote, and the part I disagree with becomes my focus. I understand that people can have a bazillion hours experience, but there is a difference between genuine experience, and extrapolating it to a different machine or process. In any case I can see more clearly it's not so much the issue at hand, more the social aspects of a group discussion where it's not clear what the other guy really "knows".

Moss, aren't you even curious why the members who don't have 120v MIGs have such dogged determination to tell the others how they can or can't be used? Why don't you encourage those who have actually HAVE a 120v MIG to go at it, show members what can be done and let's see what happens? Wheres the harm in making test plates?

It's not a matter of 'can or can't be used'. It's a matter of should or shouldn't used. There's a difference.

I've used a torch and coat hangars many, many times on thin metal. I've tried it on thick metal, too in the field. Guess what? It worked. It looked great. It worked well.... until it blew apart and I could see where it failed. Good thing I wasn't under it. Wrong tool for the job.

I've removed large bolts with small wrenches. And I've broken small wrenches. I've never broken a big wrench.

I've back-fed generators in a power outage. But I would not recommend anyone do that.

The reason I don't encourage people that have 120v MIGs to push them beyond their manufacturers' recommendations is because (to put it bluntly) the repercussions of *'ing up can be severe.

I have a 120v MIG. I love it on thinner stuff. Its fantastic. Other than tack welding, I don't use it for welding large stuff, except for a rare emergency repair, to get something to a place where I can repair it correctly. It doesn't penetrate and multiple passes by amatuers (like me) tend to look very pretty, but you have no way of knowing that they will hold until they break, which in some cases, is too late.

For most hobby users, home owners, farmers, etc... there is a place for it, however, I would definately NOT recommend a 120v MIG as a first welder for anyone. It is not versatile enough.

 

[aczlan]

I guess I should try to figure out what constitutes "pokes". I pretty much have to go on what they wrote, and the part I disagree with becomes my focus. I understand that people can have a bazillion hours experience, but there is a difference between genuine experience, and extrapolating it to a different machine or process. In any case I can see more clearly it's not so much the issue at hand, more the social aspects of a group discussion where it's not clear what the other guy really "knows".

Why would there be a difference in technique between using a 120v MIG at 130% capacity and using a 240v MIG at 130% capacity?

Moss, aren't you even curious why the members who don't have 120v MIGs have such dogged determination to tell the others how they can or can't be used? Why don't you encourage those who have actually HAVE a 120v MIG to go at it, show members what can be done and let's see what happens? Wheres the harm in making test plates?

No harm in making test plates, in fact one would be well advised to do some before trying to push their welder beyond the manufacturers recommended limits so that they know that they have the right settings (especially if they are a "hobby, farm, getter done" person who hasn't spent years welding professionally and is still getting to know their welder).
Feel free to do some "official test plates" following the procedures that have been listed and show how well your welds with a 120v mig on 3/8" plate do...

You go on and on about this being a "hobby, farm, getter done" welding forum of not professions then you say things like with proper prep, etc thicker metals can be welded. Well do you really think the "amateur/getter done" welders have the knowledge or will take the time to do the proper prep work? What this all leads to is at some point an epic fail because somebody read on this forum you can weld 3/8" with a 120 v mig welder, they won't bother to read what they need to do prep wise they will just weld it up and go.

Exactly.

Aaron Z

 

[Mark @ Everlast]

Tomorrow, I plan on doing a guided bend test over at the local tech school to make it official...but curiosity always kills the cat you know...
So. when I was cutting the plate and prepping it, I wanted to see if my suspicions were confirmed by using a "free" hammer bend test on the end pieces put in a vice. I'll bet the pictures speak louder than words. Normally these pieces are cut off and disposed of in this type of test because if you have troubles, that is where it will be. I did not round the edges or anything, but well, here are the preliminary results, which will likely be repeated tomorrow in the guided bend. I bent the face...and the result is pretty clear. I took the other end and then quickly tried it. One thing I could see was that there was a curious copper film along part of the area where it separated. Not sure that it shows up on camera. (I swapped over to a regular camara now, not clips from film for better detail) Now the wire is copper clad...and I've never liked it but that's what is available in these smaller rolls. I will still post the results of the official test tomorrow (hopefully). I am not encouraged though.

 

[MossRoad]

I advise that you not feel like you have to respond to every person who disagrees with you. Let the other person's post stand or fall on its own.
(You asked.)

Many, perhaps all, of the threads that have been closed were due to back and forth bickering, each person apparently thinking that just one more post will convince the other person they're wrong. This proceeds for more than a few cycles, with the Moderators hoping one of the participants will recognize the futility of this and simply move one. Sadly, this rarely happens. Add the fact that some people feel the need to reference previous closed threads, usually with an off topic comment like, "I hope this thread doesn't get closed like thread 'x' did.' or 'Thanks for staying on topic.' In other words, they can't let go of previous threads.

Pushing the limits of a 120v MIG welder threads will attract responses from people who feel this is unsafe as certainly as the sun sets in the west. The reader has the smarts to recognize this and can learn from both kinds of posts.

Good points, Mike. I'll bow out.

 

[Mark @ Everlast]

Summary. The welder I used is an inverter and does put out more power at a lower input amperage...so I was getting more heat than what I've seen with other transformer 120 migs I've used. If I had a 30 amp breaker the results would likely be much different as the few seconds of high power I had to work with before the breaker tripped was really fusing and wetting in. I suspect there are some more variables here. It's not the fault of the machine. I am using a C18 gas I use for both short circuit MIG and Spray arc welding and is one reason the welds look more shiny than the average MIG weld. A little more CO2 might make for a little more penetration, but I suspect not a lot to make that much difference. I was using about 20 cfh of gas flow. The issue is that most people only have 15 amps to work with. I had 20 with more available output and needed 30 and probably would have gotten better results. As you can see, the top of the weld does not tell you anything. The toes may be perfectly fused and wet in, but the underlying penetration is not there. You cannot tell if a weld is good by looking at the surface, you can only tell if it is bad. I used a 3 lb hammer...I don't know..maybe 5-7 blows before it broke and 3-4 before you could see the separation. That's really not that much when all things are considered.

Getting back to the transformer welder. Most, if not all are rated at 20% duty cycle at 90 amps. The inverter one I used is rated at 140 amps at 25%. I did not hit the duty cycle, but I was teetering on the 20 amp limit of my breaker...I think most transformers would hit the duty cycle by the end of a 6 inch plate. I need to look at the time stamps on the video I took but would think it is close to that mark. And tripping a overheat or breaker for that matter during a MIG weld will leave a weak spot where it is restarted...due to porosity or cold start. For me it seals the fate with with 120V transformer MIGs. I am still hoping that the guided bend tests may be better, and they may be...and I'll post the pics regardless. Perhaps I'll put it on a 30 amp breaker for more testing.

A couple more pictures. I think you can see the coppery residue on these. Definitely not a color shift in the camera. It's really there.