Butt welding gauge with MIG

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I've done a lot of sheet metal welding and up to around 14 gauge I have always tacked every inch around the perimeter then welded hot between 2 tacks, skipped a few, welded between another 2, etc. until the piece was complete.  The last couple weeks I've been trying to butt weld 6" lengths of 12/14/16 gauge CRS with 0.030" wire in one single pass without stopping. I tack the ends, have tried feathering the tacks, and can only rarely get a consistent weld from start to finish with complete penetration without blowing through or leaving spots where I can see the joint.  Coupons today were about 1.5" x 5" 12 gauge, tried varying stickout, travel angle, settings between 95-110A (1A per 0.001) up to 120-130A (can't remember voltage settings off hand), tested various gaps between 0.040"-0.070". My main question is: What type of motion should I be using? Straight push or some kind of weave? I find that if I push straight across, unless I haul a$$ (and even if I do) I usually end up having to release the trigger in the middle to prevent blowing through, but get complete penetration with 120-130A. I tried doing a sorta zig-zag weave thing, which helps a lot to prevent blowing through, but then I end up with gaps where I didn't completely penetrate through the back. Can anyone offer some technique tips? The way I've always done it has worked for my applications, but it ends up requiring a lot more grinding and the weld doesn't turn out pretty. Plus I would imagine that in some applications where the back can't be ground, that the extra reinforcement could act as significant stress raisers (or so I'm assuming anyway).  Thanks.
Reply:Have you tried .023 wire? if not try it
Reply:How are you determining "amps" using mig? Mig is a CV process."Amps" are often used by manufacturers to "rate" smaller class migs for use as a comparison between machines, but you set your heat using voltage. I was trying to do a but weld demo last night for a student. We didn't have any 3/8" plates beveled, so I was just using the 1/8" plates we use for other joints. 17.5 volts, wire set at 175 on the feeder using .035 solid wire 92/8 argon/CO2 on the XMT. Plates were 1/8" ( 11ga)  thick, gapped just a hair under 3/32" ( I had to use a small bit of force to push a 3/32" tig wire thru the gap as a gauge). I was pushing the bead, no motion at all. I found it tough to either burn thru or not get good penetration set up that way. ( I was trying to show him what a bad bead as well as a good bead looked like so he knew what to look out for.) Usually using those setting on beveled 3/8" plate 1/8" land, gapped 3/32" I can produce both burn thru and a section of poor penetration simply with travel speed changes. I tell students that they need to watch the puddle and manipulate it. If the gap is key holing too much, they can back up and increase their stick out as well as start swinging side to side on the joint to cool the puddle. If it's not key holing at all, they may need to close up and reduce their stick out and slow down. Thinner steel down around 16 ga or below may require almost no gap and short welds or overlapping tacks so you can control the puddle.As mentioned smaller wire can help. Post up some picts so we can see what is happening..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:DSW thanks for those tips. Since I'm using a MM211 with no gauges, and volts and amps (wire speed) are listed in handbook/guidebook welding procedures, I ignore the machine's chart settings and tune the machine with my fluke meters (136 clamped around the ground and 115 voltage from hot peg to ground clamp) to what i find in wire manufacturers guidebooks.  I've been quoting amp numbers instead of wire speed only because the wire feed motor is coupled to the welding circuit on these models so wire speed fluctuates slightly under load and due to wire tension as well, and by videoing the meters I have easy access to amperage info.I've been using C25, but I think voltage around 18.5V, I wrote it down, will check in a bit, pretty sure I've been using a higher voltage than your setting (but with C25) maybe that's where the burnthrough issues are coming from. I'm always hesistant to use a lower voltage than what I find in manufacturer's procedure guidelines, maybe to my detriment, but I'm usually more worried about lack of penetration. Also I find it tricky to keep a very steady motion sometimes. I can usually see/hear when the weld is about to burn through and let off the trigger. Often I feel like once that point has been reached even a longer stickout will sometimes burn through quickly after. When I say lack of penetration, usually I get full penetration on 95-98% of the weld, just a few spots where I can see the joint, this I'm trying to avoid. I'll post some pics in a few hours. I have another gun setup for 0.023/0.025" wire, but even the thinner stuff should be doable with 0.030"Thanks again.Last edited by Jieve; 03-13-2015 at 12:51 PM.Reason: wording
Reply:C25 is what I use at home on my machine. 92/8 is what the school uses since they also do spray with their machines. Settings on volts/wire will differ slightly but are reasonably close. Settings we use are fairly close to what Miller suggests for volts/wire on similar material on their charts for the MM 252 using C25.18.5v / 200 wire speed is about what we often use on flat joints like filets. It's doable on gapped but joints but a bit harder to control. It's been a bit since I tried to run one that hot. It's certainly hotter than I'd want to run on thinner stuff.Trying to explain how to see and read the puddle is one of the hardest things I've found to convey to students. Some pick it up right away, others it just takes longer. I had one student last night I spent quite a bit of time with trying to get this across. He's close, but I don't think he's quite made all the connections yet. It's tough many times to try to explain the minor adjustments that are needed to do things like this if you can't read the puddle..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I'd drop wire size. Are you using push or pull? A while back I messed around welding banding one afternoon. Direction and angle can really affect the heat taken up by the part. http://weldingweb.com/vbb/showthread.php...ing-band-steelCan you clamp on a copper heat sink?
Reply:I'm a hobbyist.  I do a lot of welding sheet metal (12 to 18 ga) using butt joints.  I have .030 wire in my mig.  I use push technique, sweeping back and forth in front of the puddle.  To keep things cool I only go about an inch or two at a time.  mbMetal bending since 2004Millermatic 211Maxstar 150sth
Reply:Ok, so looked up the settings I used. Mainly alternated between 120-130A @ 19V and 100-110A @ 18.6V.  Interpolating for 12 gauge using Miller's online calculator they recommend 18.5-19.5V, but I assume that this is for fillet welds, so looks like my voltage was probably high, but that's where I got the info I was working with.  In another post someone had given me aluminum settings from a MM252 chart, voltage was WAYY lower than I'd found in any procedure handbook, so was a little skeptical of that.Pics: 1st 100-110A @ 18.6V, Weave - Top2nd 100-110A @ 18.6V, Weave - Bottom3rd 120-130A @ 19V, Weave - Top4th 120-130A @ 19V, Weave - Bottom5th 120-130A @ 19V, Straight - Top6th 120-130A @ 19V, Straight - Bottom
Reply:Weaves seemed to leave me with crappy penetration, going straight was best at the higher settings but tough not to burn through. I tried amperage between those two extremes, had similar issues, either too much or too little. Maybe the voltage is too high. Used a push angle about 45 degrees for all of these. Not using a heat sink, was wanted to get this down solid without having to use some kind of copper backing in case that isn't possible. DSW, when you mention keyholing, can you explain exactly what you mean by this?Would also be great if someone could post some pics of what the joint should look like, so I know what I'm aiming for.Last edited by Jieve; 03-13-2015 at 02:36 PM.
Reply:Key hole is when the sides of the pieces open up usually in a round fashion, so the shape often looks like an old fashioned key hole in a lock.Top definitely looks hot and travel speed looks a bit fast. Back looks decent except the left side of the 1st pict of the back. Can you tell me how each back relates to the front picts? I can't tell from the ends which one goes with which ( assuming they aren't different). Picts 1-4 the ends don't seem to match any shown that I can tell. Pict 5-6 looks like they may be back and front, but if so, the back is also flipped end for end as well as over. I see the plate extending to the bottom right on pict 5, but then it's extending to the bottom left on pict 6 so I'd guess it's rotated as well as flipped.If matched the way I think they are, pict 1 I circled the area in red where it looks like you were moving too fast. I also circled the matching are in pict 2 that corresponds to what I see on the top in red.Picts 3 and 4, I circled  what I think are matching areas in these where it looks like you have a bit more penetration. The areas I circled in green the penetration looks like what I'd usually be looking for with students. The yellow area may be a bit light on penetration. Hard to see in that pict exactly where the original edge of the plate falls in comparison with the penetration. It looks like the edges broke down 100%, but it's close. None on the back look excessively over penetrated or that they have too much reinforcement on the back..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:.No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Wow, awesome feedback, thanks!!!  Yeah, you're right about me having rotated the pieces, pics 1 & 2 are front and back of the same weld, pics 3 & 4 are a single weld and 5 & 6 are a single weld. Out of the 30 or so tests that I did, I think the one in pics 5 &6 was one of the better, I was able to run that all the way across without stopping or burning through. But I'm thinking you're right about the voltage, probably need to cut back. I ran out of 12 gauge sheet but have some 14 Gauge and 1/8" to practice on, will try dialing the voltage back on those and see what I can come up with. With regard to the keyholing, you're referring to what the weld puddle looks like just prior to blowing through, right? And as soon as I can see that, it's time to increase stick-out? That widening is usually what I notice when it's getting close to blowing through. I'm finding that whenever I use handbook procedure values for my settings, the voltage seems high, but I'm reluctant to dial back. I think this is holding me back a bit from getting solid butt welds. Fillet welds take the heat a lot better.
Reply:I'd agree picts 5-6 are pretty decent, but could use some work to improve them some. I have to run go do an estimate right now, but here's an example of a keyhole I found on line.You can clearly see the hole open up as you weld in many cases, though not always. If everything is right, the hole simply stays that size, and you fill it as you go. If you are too hot, your gap gets too big etc, the hole will keep opening up until you loose control. Where you need to start dealing with the heat comes from experience. You learn to note the subtle signs that tell you things are just about to fall apart and you will loose control. At that point, you need to start trying to close up the hole or decrease your heat. Moving up on the sides some using a V or circular motion some times helps, or back up the gun slightly to increase your stick out. It's like driving, I can't tell you how much to push down the gas pedal to drive 35, or how far to turn the wheel on a corner. It's something you gain thru experience. What works for me may or may not work for you..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:It's hard to say without wire speed numbers, but 18 - 19V seems high for .030 wire and 16 to 12 ga steel. You can calculate wire feed speed by feeding wire for 6 seconds, measuring length of wire fed, and multiplying by 10. Off the top of my head I'm thinking 15.5 to 18 volts and 150 - 300 ipm. Double-check that your charts are for 75/25 gas. Voltages for 75/25 are around 1V less than for 100% CO2.I disagree about going to .025 wire. With those gauges you are right in the sweet spot for .030 wire.Also: practice, practice, practice! Getting even penetration on a MIG bead requires a steady hand and consistent travel speed. Settings and travel speed are also dependent on joint geometry and fit-up. Experience really helps here.JohnLast edited by Silicon-based; 03-13-2015 at 09:46 PM.Reason: Add info.A few weldersA lot of hammersA whole lot of C-clamps
Reply:DSW, thanks so much for taking the time to critique and review my welds in the detail that you did, plus the super fast responses. Really appreciate it.John wire speed is around 315 ipm, voltage could probably come down some. As I mentioned above, I'm not going off the machine chart, but measuring the voltage amperage with meters and going off a combination of Miller's online calculator (i use these values for fillet welds), the 1 amp per 0.001" rule of thumb for gauge thicknesses (for butt welds), and Lincoln's gmaw guide procedures. I have been using the voltage from the miller calculator fillet weld settings for butt welds as well, so as you and DSW mentioned the values are probably high. Was practicing on aluminum square tube most of the day today but will get back to steel and turn it down some.
Reply:DSW, so I spent a number of hours today practicing cjp butt welds from one side on 1/8" mild steel with 0.030" wire (square butt joint, 0.09-0.1" gap). I converted the 0.035" ipm you listed above into amperage and set the 0.030" wire speed for that, and upped the voltage to 18V. I finally was able to understand what you meant by watching and reading the puddle. I've always butt welded so hot that there never really was any time for keyholing to start to take place, or time to adjust stickout to compensate, I always just instantly blew holes when things got too hot. I've had to weld way slower than I'm used to but now with great results. Thanks for the tips, very excited about it. Would you be willing to divulge the settings/technique (nr passes, bevel, gap,  torch motion) you would use with 0.035" wire when butt welding 3/16" and 1/4" from one side (or both, for that matter) with cjp? Would greatly appreciate it, wanna start working on that next.
Reply:Wire feed speed controls amps but you need the right volts to get the desired bead. Higher volts give a wider flatter bead. Try positioning the plates so you are welding downhill somewhat. Doesn't have to be right vertical but then you could use a pull technique and be able to see what going on easier. kind of like doing a root pass. I think somewhere around 17 volts and 100 amps should be close. I'm not sure what wire speed would give 100 amps.
Reply:Welder Dave, thanks for the response, with the 17V/100A are you referring to butt welding 3/16" and 1/4"? I was able to optimize my 1/8" butt welds with 0.030" at 18V and 105-110A (something like 270-280 ipm), would go up to 0.035" for the thicker stuff
Reply:Glad things worked for you and you are beginning to understand. Always nice when someone I help has one of those "Ah ha!" moments and begins to make the connections to what I have been trying to explain.The numbers I gave before were those we use on 3/8" beveled but joints. 17.5v /175 wire, 0.35 solid wire, 92/8 gas, 3/32" gap, 1/8" land, I forget the bevel angle off the top of my head, but it's cut with the track torch set for practice aimed for pipe, so I'm guessing in the 35* range or so.. Some will reset the machine  hotter if doing those joints flat/horizontal once the root goes in, for subsequent passes, jumping up to about 18.5 /200 wire. for 3/8" plate, it's usually 3 passes and a weave ( root, two over that, then the weave to cap) or 6 passes if doing stringers, ( root, two, then three on top). Depends a lot on how you weld. Some lay in really small tight beads and can do 6 plus still have the room to weave a cap. Others go almost flush with just 3 and have to either back off a bit on how much they fill, or up the fill to get above the plate surface.As you improve, you'll find you can handle different gap/land tolerances or voltage wire speed settings. Once you learn to read the puddle and manipulate it, you will begin to automatically make changes to deal with what you have to work with, even if the settings are not optimal. You change your travel speed, stickout, gun motion based on what you see happening. There are times I can start welding and stop almost immediately knowing the settings are "wrong" for what I'm working on that day, even if they have worked on similar joints dozens of times before. I may have to bump things up or down a volt or 2 and adjust wire accordingly. Same goes for wire speed. I may have to bump it up or down from those numbers for the machine I'm using if things aren't sounding/welding the way I want..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Great, thanks for that response. So I'll stick to those settings and keep the land at 1/8", gap 3/32" and bevel what's leftover on the 3/16" and 1/4" to a 60-70 total angle (both pieces). From what you're saying, it sounds like 2 passes are to be expected on those, 1 root and 1 stringer/weave (probably weave on the 1/4"). I'll give it a shot as soon as I get the chance.  Thanks again for all of the useful info and taking the time to help.
Reply:So, I spent the better half of the day a few days ago attempting to achieve cjp on 3/16" butt welds. First attempt: 0.035" wire, 60-70 degree included angle, 3/32" gap, 1/8" land, 17.5V, 175 ipm wire speed. I beveled the pieces using a flap disc, and had difficulty getting complete penetration on the tacks. Also couldn't really get complete penetration into the joint ... it seemed like the bevel was way too narrow and the wire wouldn't really get down into the joint.Second attempt: Same setup as above, but widened the bevel angle to a total included angle of 120 degrees. This worked better, filled the root but still had some penetration issues. The finished root pass was about 1/16" below the upper surface and would have required a second cap pass.3rd - 15th attempts: Instead of beveling, I decided to try a square butt joint. I tried a number of settings but I settled on the following: 0.035" wire, 1/8" gap, 19.5V, 290 ipm (160-170A). This was on 2" and 3" square tube 3/16" wall thickness. Tacked the corners, feathered and ground tacks, and was able to weld with complete joint penetration relatively consistently with the above settings. The bead ended up pretty flush with the surface, hard to say how much I would be able to grind flush. However, I'm having issues tying the bead into the tack at the end of the run. It seems like no matter how much I feather them, and shove the gun down in the joint, I have the same issue, lack of penetration just before the end tack. Anyone have any tips on what I'm doing wrong? Do I just need to turn it up a bit? Are my settings/gap/technique ok?   Thanks. Pics: 1) Setup and Tacked2) Tacks ground and feathered3) Seam welded4) Backside of joints
Reply:Nothing wrong with that.
Reply:Thanks welder dave. It's about 98% there, its a little hard to see in the pic but if you look closely at the end of each run, the weld doesn't go completely through the back for like 1/16" before the end tack locations, even with them feathered. The starts are fine.Not sure why this is happening, anyone have any tips of what I need to do fix that?
Reply:Ok figured it out. Wasn't feathering the tacks down as far as I needed to, cutting them down to about a sliver solves the issue and i get full penetration.Btw the wire speed nrs i posted above were ok, but the amperage was off, turns out with the average stickout i've been using on 3/16" it's 145-155A, 19.5V.