Mig welding on mill scale, will it make a difference ? 🧐

[@davewheeler5850]

Awesome comparison, thanks for sharing 👍

[@ls2005019227]

Great tests & video! Prior to seeing the results, I would have assumed there would be a difference- Thanks!

[@makingmistakeswithgreg]

I thought there would have been a noticeable difference too. I retested this with fillet welds out of curiously and will be putting that video out soon. I think it helps having some skill and around 180 amps. Had I used a 140 amp MiG welder it would have likely made much more difference lol.

[@markdeitchman8938]

thanks Greg for doing this test. I am trying to learn. I assume you are saying your settings 21.5/300 yielded around 180 amps. is this right? also, are you saying if you had run at lower settings like 17/170 (for a 140 amp mig welder) that there would be a notable difference (between mill scale side and clean metal side)? why do you assume the results would have been different? I know you were testing 1/4 inch plate. why would the test results have been notably different at lower settings? maybe they would have been the same on both sides too? I appreciate your efforts! @@makingmistakeswithgreg

[@makingmistakeswithgreg]

@@markdeitchman8938 hopefully this helps: There becomes a point with short circuit MiG process where it simply doesn’t have enough heat input for material thickness. A 140 amp Mig welder is capable of welding 3\16th thick material in a lap joint/fillet weld with root penetration. When you step up to 1/4in plate there simply is not enough heat input to get any root fusion. The only way to get proper root fusion with a 140 amp MiG welder on 1/4 inch plate is to switch to flux core wire, which will have solid root fusion/penetration. This can be confusing because stick welding at even 90 amps has no issue with fusion on 1/4in plate, but stick operates at 23-30volts so 90 amps has way more heat input than a 140 amp MiG welder. Example: a 6010 at 90 amps (which runs at 30 volts) is 2700 output watts. Short arc Mig at 140 amps at 18v is only 2520 watts. Combine this extra heat input with the benefits of the flux system and it’s easy to see why stick will weld thicker material at lower amperage than MiG will. In my testing if I had tried to run values similar to what a 140 amp MiG welder could achieve, the penetration would have likely been noticeably different between sides. I was carrying enough heat in this video that the difference mill scale offered seemed to limit the effect to cosmetic results mostly. With less heat the difference would have been far more than cosmetic I believe. I have a video coming out shortly where I weld 3/8th plates at values just above the 1/4 inch plate in this video. The results show poor performance, as expected. A general rule with short circuit Mig is a 200 amp welder is only practical up to 1/4inch plate with short arc gas shield. 140 amp welders are only capable of welding up to 3/16th plate with gas shielding. To demonstrate this fact I will be welding chain hooks to a piece of 3/8th plate with both MiG and stick to show actual differences. Also, yes 21.5 and around 300 showed somewhere between a actual 170 to 180 amps output on my welder when I previously clamp metered it. Wire feed speed dictates amperage because output amperage is controlled by how much current it takes to continuously clear the “shorted” MiG wire. My machine is labeled as a 200 amp MiG but some of the internal charts values (like for 3/8th plate) actually exceed 200 amps of output. Even at 200+ amps the welder still won’t have much penetration on 1/4 and especially 3/8th material. The reason is limitations of the process. When you switch to spray arc (which requires more voltage and amperage than my welder can supply) you can weld 3/8th thick steel without any issue with the same wire I was using. It just takes 6+ more volts, 50+ more amps (via high wire feed speed) and a different shielding gas mixture.

[@markdeitchman8938]

appreciate your explanations. also appreciate the time you took to reply. very helpful. @@makingmistakeswithgreg

[@Justforfun-ek7et]

I helped a buddy of mine build a bumper and I told him we needed to clean all the weld spots off before we welded so it wouldn’t break down the road when he’s winching himself out of a ditch, he chose not to spend the time removing the mill scale. . During the cooling periods after we laid down some serious beads you could hear the metal clanging and popping very loudly… I wasn’t able to see any cracks anywhere but I think we had some welds that separated.

[@makingmistakeswithgreg]

With MiG it definitely is smart to prep all the material. It does have some ability to weld through milscale (as this video and a few more that are coming out show) however I am running decent values and competently welding them. At reduced values or doing things like “riding the puddle” is where major issues come into play, and the scale could be a major factor. Especially because Mig has such limited penetration to begin with. Sounds like you had the right idea on prepping, but sometimes you have to deal with what you have 😀

[@Justforfun-ek7et]

@@makingmistakeswithgreg no doubt, as the more experienced welder I should have forced him to listen to me but he was “the customer” and wanted what he wanted 😂 I did increase the heat a bit to get better penetration but only time will tell. Funny enough I asked him to let me stick weld it but he wanted the welds to look pretty. They did look pretty at least! Thanks for all your help and input!

[@michaelwhiting878]

Very interesting test, but I was wondering if there may have been more of difference if the one side of your coupon wasn’t ground down to shiny metal. One would think connecting your work lead to heavy rust or mill scale (or placing it on a grounded table like yours), would make for a higher resistance circuit and therefore less penetration. If you preform this or a similar test again, perhaps use two coupons from the same source with one cleaned and the other covered in heavy mill scale. Additionally, I really enjoyed your recent video about removing mill scale and resurfacing your welding table. It was very applicable to this video. Personally, I’m one who cleans both the weld area and work clamp down to shiny metal, and when I place the piece on my welding table, I make sure it is well grounded, and will place something like a weight or clamp it down to give the best ground possible (within reason), or I will find a way to connect the work lead directly to it. If I need to do a restart, I always make sure the weld area is just as clean as at the begging regardless of which process I’m using. Perhaps that’s overkill, but it’s not worth risking a crappy weld. However sometimes your situation prevents properly preparing your weld area, and you just have to do the best you can.

[@makingmistakeswithgreg]

So the main culprit with poor grounds is arc stability issues. As the ground clamp intermittently breaks circuit due to poor contact you will momentarily produce a poor weld. With flux core wire it’s almost guaranteed porosity, with Mig it will produce no penetration at that point due to heat input loss. With stick it will often either cause a stuck rod to the material or serious arc blow. It definitely can be a huge issue. More than I would like to admit I was welding on a truck or something and a poor ground caused some weld defects. Cleaning the ground clamp area is the best solution. As far as the plate test I did, there are some interesting variables I didn’t account for. One being that the welds on the first side would have raised the plate up and reduced the heat sink effect of having the plate physically touching on the table. The 1/4inch plate is thick enough that I believe the effect would have been minimal but it still could have effected it. The beads touching the table rather than the plate would have also reduced the number of potential ground paths which could change the arc stability. All interesting things and I will take all the notes and do some more testing. I have already shot/edited 3 more actual test videos, (one on 3/8th, one on “circular e” vs straight in, and one on 1/4in fillet welds) but I was planning on doing a nice comparison between flux core .035, hard wire MiG .035, and mig with 100% CO2, so I will surely do a good job to make everything fair and balanced in that test 😀

[@brianhowe8896]

Would there be any difference between the clean and mill scale sizes in terms of earth problems. Both sides just sit on your welding table?

[@makingmistakeswithgreg]

Realistically I would say no. Once a path to ground is established it’s fine. Occasionally work pieces will get “stuck” aka fused to the table due to it arcing/melting to the table. I should build a copper “3rd hand” in the future to eliminate that. The main thing a initial poor ground affects is the initial start of a weld, it can be rough/have arc wandering.

[@jimmywilson1388]

I’ve got a good idea for a video. You should build an exhaust shroud with some duct work or something so your videos will turn out better. I think the image quality would look great if you had fan pulling the smoke away.

[@richg1309]

First! Woohoo! Great topic Greg.

[@makingmistakeswithgreg]

Congrats lol 😀.

[@ajkiviaho7212]

So I would like to see you run flux core / stick / mig welds no clean up … most intrigued about flux core / stick 7018/6010-6011 just where does flux core compare with stick .. is it the same or better then stick

[@makingmistakeswithgreg]

So I have done cut and etch’s directly on flux core and stick, but I will definitely do a video comparing all of them together. In my testing there is no question flux core is far better than mig, and stick is better than flux core depending on rod. Flux core produces a weld/penetration similar to 7018 but slightly different shaped. The best penetration I have seen is 6010, which is shockingly better than 6011. I will do a video on this shortly to really see the differences 😀

[@ajkiviaho7212]

Thank You look forward to see that@@makingmistakeswithgreg

[@PiritTV-k1i]

Cool. Can you try with flux cored(FCAW) if it will make a difference.

[@makingmistakeswithgreg]

I have covered FCAW in previous tests (my Mig vs flux core strength video under how to mig weld series) shows some differences. However I will be doing a lot more tests just like this video with other processes like flux core😀.

[@ajkiviaho7212]

For example Lincoln NR211 MP flux core no additional gas .035 … I don’t trust the GS series flux core wire because you can’t run multiple passes

[@makingmistakeswithgreg]

Yes, the GS standard basically has minimal testing requirements. It’s possible it is the same wire as say a nr211, however it doesn’t have to meet many specs that Lincoln’s wire does. Much like rods that hardware stores sell that are “steel weld rods” with no “6013 or 7018” classification, -gs flux core wire is basically minimal standard. Fine for yard art, not something I would want to use on critical jobs lol.

[@ajkiviaho7212]

Thanks for the explanation .. now I know more then I did before I read this post .. Cool !!@@makingmistakeswithgreg

[@mikeuhlmann6825]

I don`t trust welds running over mill scale. If i can reach a weld area with a mig gun, i can reach it with some kind of a cleaning tool, like a flexible shaft for a drilling machine. Sometimes it`s just 30 minutes of cleaning to be sure, that your weld is safe. I take my time to prepair and none of my welds has ever failed. It`s still nerv wrecking, when my welds come to the test....

[@makingmistakeswithgreg]

100% agree.