Millscale

admin

Many times we are asked "What is Millscale?"Millscale is the crappy finish that comes standard on HOT ROLLED steel...Don't matter if it's plate..round stock..flat stock..or angle..If it is hot rolled it has Millscale.And if you are going to TIG weld it...IT MUST GO!!!Below are two plates that are hot rolled and have the standard Millscale on them..In pic 1 there is the grinder with a hard disc on it...After grinding the surface it looks like this..You can remove it with the hard disc and what I like to do is hit it with a flap wheel after..When all said and done your parts should be nice and shiney like this..One quick wipe with acetone on a clean rag after grinding and you are good to go..You don't need to grind the whole surface but you do have to GRIND WHERE THE WELD IS GOING!!!!(I only ground the plates because they will be painted after assy...That's for another thread in projects and pictures....Kinda killed two birds with one stone..)So GRIND OFF THE MILLSCALE especially before TIG welding!!!...zap!Last edited by zapster; 01-18-2012 at 04:49 PM.I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterMillscale is the crappy finish that comes standard on HOT ROLLED steel...
Reply:Originally Posted by GambleWhat about cold rolled? How can you tell the difference between hot and cold?
Reply:Zapster. I hate to argue with the moderator but this mill scale thing is really scaring me. You make me think after almost 40 years under the hood I done it all wrong. I cant go back and do it over because I dont think I will live that long. I never have cleaned the millscale off before welding. Worked in some shops that shot the gray primer on tanks that you had to grind before being able to weld on them. Even with the wire welders I havent ground off millscale. I hate wire welders. Millscale comes off when hit with heat. Be it with a torch or a welder. I have burnt some off to be able to make a good solid mark with a soapstone for cutting . Sorry I have to disagree with you but its what makes this a free country. I hope you come back on this and not just delete it. Thanks Harold
Reply:I would like to know why I get better looking welds with mill scale on and when grinded off my welds don't look at good.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by WelderskelterZapster. I hate to argue with the moderator but this mill scale thing is really scaring me. You make me think after almost 40 years under the hood I done it all wrong. I cant go back and do it over because I dont think I will live that long. I never have cleaned the millscale off before welding. Worked in some shops that shot the gray primer on tanks that you had to grind before being able to weld on them. Even with the wire welders I havent ground off millscale. I hate wire welders. Millscale comes off when hit with heat. Be it with a torch or a welder. I have burnt some off to be able to make a good solid mark with a soapstone for cutting . Sorry I have to disagree with you but its what makes this a free country. I hope you come back on this and not just delete it. Thanks Harold
Reply:Originally Posted by GambleI would like to know why I get better looking welds with mill scale on and when grinded off my welds don't look at good.
Reply:Well if you don't know I'll never figure it out. I thought it was just me, but I guess not.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Zapster. I stand corrected. I apologize. I did miss that part. I would have to agree. Harold
Reply:Originally Posted by WelderskelterZapster. I stand corrected. I apologize. I did miss that part. I would have to agree. Harold
Reply:So what are other differences between HRS and CRS?Strength?Cost?Warppage?Good thread Zap. Love to learn.~RocklandMillermatic 211
Reply:Wow and all this time I thought it was something my dentist said I had.Seriously though even with stick welding I clean scale of when using 7018, not really necessary with 6010 but beads look better if you do.On  scale removal Crest works ( Opps ) I mean disks work betterr than flaps and hitting it with the grinder first then lightly flapping saves on flap disks. And boy sometimes you can run into scale that is just tough and nasty and thick, 7-9 inch grinder time I got some 3/4 plate outside like that.
Reply:one more thing to throw in there is that wire wheels are in no acceptable to remove scale, they only polish the scale.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Will a flap disc by itself remove mill or just polish it?Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:You can wear a ditch in a piece of iron quickly with a flap disc.
Reply:Originally Posted by GambleWill a flap disc by itself remove mill or just polish it?
Reply:Hello Zap, I can maybe add a few other items that might give some credence when you are "allowed" to remove mill scale before welding. Mill scale is a form of oxide, it requires more energy to melt it and consume it in the welding arc than the "pure" metal that is presented to the arc/weld metal. When you weld on cleanly ground metal, especially hot rolled plates or other shapes, the aesthetics and often the mechanics of the weld will be of higher quality. The toes of some welds will exhibit undercut, lack of fusion, and microscopic deficiencies when welds are done without scale removal. Out-of-position welds will especially show effects of not removing scale more so than other weld positions. Run just about any weld joint in the vertical position with SMAW, FCAW, GMAW and the joint that has been ground will turnout looking better and will generally be easier to control and yield a higher quality weld. Even these very small or large deficiencies (if it's deep and long undercut) can cause stress risers and similar problems that could result in weld failures. Amount and thickness of mill scale will vary widely with plate thickness, manufacturing process, and many other variables. Industry, application, process (in this case GTAW) and sometimes fabricator/welder craftsmanship could be the determining factor as to whether scale is removed or not. In some cases, referring to industry, removal of scale, rust, oxidation (from thermal cutting processes) galvanizing or similar surface applications, and other foreign materials, is absolutely required before welding can be done. I believe many items welded for military applications definitely require removal, at least the ones that I was associated with did, and a lot of the other governmental agencies requiring metal fabrication had similar requirements. Removal of mill scale will ensure better quality when applied to welding. With my comments here I don't say that all welds require scale removal to be "correct" or of quality, I simply say that a few minutes with a grinder will certainly be appreciated when you get to the welding end of things and possibly the look of the bead afterwards. Economics along with a number of other requirements will likely dictate in an industrial context whether you will or won't. Best regards, Allanaevald
Reply:I tried my toothpaste but it didn't work. Does it have to be CREST brand?What about Tabasco? I think that works on pennies.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by zapsterMany times we are asked "What is Millscale?"Millscale is the crappy finish that comes standard on HOT ROLLED steel...Don't matter if it's plate..round stock..flat stock..or angle..If it is hot rolled it has Millscale.And if you are going to TIG weld it...IT MUST GO!!!Below are two plates that are hot rolled and have the standard Millscale on them..In pic 1 there is the grinder with a hard disc on it...After grinding the surface it looks like this..You can remove it with the hard disc and what I like to do is hit it with a flap wheel after..When all said and done your parts should be nice and shiney like this..One quick wipe with acetone on a clean rag after grinding and you are good to go..You don't need to grind the whole surface but you do have to GRIND WHERE THE WELD IS GOING!!!!(I only ground the plates because they will be painted after assy...That's for another thread in projects and pictures....Kinda killed two birds with one stone..)So GRIND OFF THE MILLSCALE especially before TIG welding!!!...zap!
Reply:So zap I take it that the orange haze that was around my practice beads were from the mill scale on the metal.Will   Supports Autism Awareness                            My ToysBobCat 225 PLusMillermatic 130Miller Spectrum 300 CutmateEverlast Power Tig 185 Micro April is Autism Month .
Reply:Originally Posted by aevaldHello Zap, I can maybe add a few other items that might give some credence when you are "allowed" to remove mill scale before welding. Mill scale is a form of oxide, it requires more energy to melt it and consume it in the welding arc than the "pure" metal that is presented to the arc/weld metal. When you weld on cleanly ground metal, especially hot rolled plates or other shapes, the aesthetics and often the mechanics of the weld will be of higher quality. The toes of some welds will exhibit undercut, lack of fusion, and microscopic deficiencies when welds are done without scale removal. Out-of-position welds will especially show effects of not removing scale more so than other weld positions. Run just about any weld joint in the vertical position with SMAW, FCAW, GMAW and the joint that has been ground will turnout looking better and will generally be easier to control and yield a higher quality weld. Even these very small or large deficiencies (if it's deep and long undercut) can cause stress risers and similar problems that could result in weld failures. Amount and thickness of mill scale will vary widely with plate thickness, manufacturing process, and many other variables. Industry, application, process (in this case GTAW) and sometimes fabricator/welder craftsmanship could be the determining factor as to whether scale is removed or not. In some cases, referring to industry, removal of scale, rust, oxidation (from thermal cutting processes) galvanizing or similar surface applications, and other foreign materials, is absolutely required before welding can be done. I believe many items welded for military applications definitely require removal, at least the ones that I was associated with did, and a lot of the other governmental agencies requiring metal fabrication had similar requirements. Removal of mill scale will ensure better quality when applied to welding. With my comments here I don't say that all welds require scale removal to be "correct" or of quality, I simply say that a few minutes with a grinder will certainly be appreciated when you get to the welding end of things and possibly the look of the bead afterwards. Economics along with a number of other requirements will likely dictate in an industrial context whether you will or won't. Best regards, Allan
Reply:Originally Posted by SteelwillSo zap I take it that the orange haze that was around my practice beads were from the mill scale on the metal.
Reply:Originally Posted by rocklandSo what are other differences between HRS and CRS?Strength?Cost?Warppage?Good thread Zap. Love to learn.
Reply:Originally Posted by scudzukiCRS is more expensive.
Reply:Wow thats alot of interchange about millscale, one thing that will remove it is Apple Cider Vinegar, the thicker the millscale the longer the soak time, Muratic acid will do it faster but is very hard to be around, burns the nose and rusts everything around08 Lincoln Ranger 250 w/Remote94 Lincoln G9 Pro68 SA-200 Red FaceLincoln 250 Idealarc w/remoteMiller 250 SyncrowaveHere's a method I have found a bit easier if you hove lots of mill scale to remove and about the cost of a disk. http://weldingweb.com/vbb/showthread.php?t=32280
Reply:Proving once again ..That you weld metal.  Attempting to weld 'non-metal' (rust, mill scale, paint, other oxide forms, grease, oil, the neighbors cat, etc) may or may not result in 'acceptable' welds, depending on the welding process used, the base metal trying to be welded, the specific 'non-metal' in the way, and so on.GTAW aka TIG welding 'tolerates' the least amount of non-metal in a weld of most common arc welding processes.  Mill scale is not metal.  The best laid schemes ... Gang oft agley ...
Reply:What if you put the metal into a bucket filled with water and baking soda and ran current through it.Details here:http://www.thepontiactransampage.com/rust.htmlI had someone try this on their gun barrel after the house was on fire and he was trying to rebuild it. It came out nice after it. But I'm sure you have to wash it with hot water so it doesn't flash rust.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by GambleWhat if you put the metal into a bucket filled with water and baking soda and ran current through it
Reply:Something I didn't know was that welding material with oxide on will produce more fumes than welding metal that has the oxide removed.  Many shops I have worked in would consider showing you the door if you removed the scale.  They have not allocated the time and discourage it.  In one shop after being told not to remove scale next to the weld I just removed the scale when the foreman was not around.  When he was watching for maximum production I left it and welded.  This is for GMAW.   In the end, removing scale cannot hurt and often will help getting that last little bit of perfection whether is it is neededor not.
Reply:will paint adhere to mill scale and be a durable finish if you use a self etching primer?bobs77vet/37ford4drEastwood digital TIG200HH190Lincoln Invertec 155sLincoln weldpak 100sears/craftsman (lincoln) 50a 240v buzz boxO/A rig Harris gaugesnexion cut 50 dxchicago electric (HF) 240v spot welder
Reply:There are several levels of paint finishing.  Sandblasting of course Is the best.  Usually a good power wire brushing will remove any loose scale.  Wipe down with thinner to remove any dust or physical dirt then primer.  At that point the scale will not come off under normal circumstances.   One structural painter told me that the better paints are ones heavy with oil that take extra long to dry are best.  He had no respect for fast drying paints on exterior structural.
Reply:There must not be much of any mill scale on 4130 tubing.  I've never bothered to gring away at the finish and it welds up beautifully.  HR plate is a different story though.  I always grind a clean surface on it prior to welding.  I assume acetone alone cannot remove mill scale?"There are two types of people in America - those who try to classify everyone into two types and those who don't."
Reply:Originally Posted by SuedePflowThere must not be much of any mill scale on 4130 tubing.  I've never bothered to gring away at the finish and it welds up beautifully.  HR plate is a different story though.  I always grind a clean surface on it prior to welding.  I assume acetone alone cannot remove mill scale?
Reply:Originally Posted by ZTFabYes there is.I prep all of my tubing by sanding off the coating in any area(s) that will be welded. If you think that it welds just fine without taking it off, clean it and you'll be amazed at the difference.
Reply:Originally Posted by dstevensWhat are you using?  I'm using Scotchbrite purple and acetone.
Reply:ZTFab, That is very nice fitup. It sure makes it easy to weld when its clean and fitted like that.Again very nice work www.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:My electrical operated spooge tank will take it off.  However the other day I bought some hot rolled sheet stock and made some covers for a band saw and then I ran them in my spooge tank and before treating them they were covered with very slick blue scale.  after cleaning them to shiny metal there were many small hollows and indentations that the scale had been hiding.  I've never noticed this before.  Mac
Reply:Originally Posted by ZTFabEither one of my Burr Kings or a DA sander with an 80 grit disc and then a wipe down with acetone after either process.
Reply:Originally Posted by ZTFabYes there is.I prep all of my tubing by sanding off the coating in any area(s) that will be welded. If you think that it welds just fine without taking it off, clean it and you'll be amazed at the difference.
Reply:Originally Posted by SuedePflowI'll give it a shot next time we weld up some 4130.  I just picked up a DA yesterday.For reference, here's some pics that show the surface and minimal prep prior to welding.  We may have lightly hit it with a wire brush prior to welding, but it came out pretty good anyway.  I look forward to gauging the difference after hitting it with a DA.
Reply:I'm not familiar with what SMW is.  I know we use regular ER70S-2 filler on 4130 tube.Beautiful welds, btw."There are two types of people in America - those who try to classify everyone into two types and those who don't."
Reply:I think the clue here, is that anything that looks distinctly different (bright and shiny) after sanding or grinding, must have had some kind of scale or oxide layer on the surface. We all know what "black pipe" or "structural steel" looks like, it sure ain't shiny. It is the mill scale that makes it that darker color.Cheers,  Tony._________________________________Transmig 310 + Argoshield LightOxy acetyleneOxy propanePrehistoric stick welder_________________________________
Reply:i have some 1/8" or i think its also 11 gauge steel i dont know if its hot or cold rolled but i think its hot and it takes forever to get to clean metal with a DA flap or the 90 sander. I dont want to use a grinder disk it cuts to deep i want as much metal as i can. What is a faster way i looked and muriatic acid seems to do the job and great for the price $3 a gallon anything better.I would also like to know do you clean the metal shiny thin use weld primer and does it penetrate and ground good thur this primer like clean metal.Last edited by mafiacustomz; 04-21-2012 at 02:31 AM.
Reply:As a bit of a follow-up;  we hit some 4130 tubing with a DA and welded it up.  It makes for a more colorful weld, but it otherwise welded up the same with or without scale.  Maybe this tubing I buy is just cleaner than most others?  It seems that this is the only material that I don't have to spend time cleaning up before welding..."There are two types of people in America - those who try to classify everyone into two types and those who don't."
Reply:Nice work ZT, those r some some nice lookin welds all I know is HRS welds 10x better when you take the millscale off.  However you want to take it off, just make sure its gone http://www.philswelding.com
Reply:You can wash it by leaving it in water containing washing soda or detergent, it would remove rust to some extent.
Reply:Originally Posted by 37ford4drwill paint adhere to mill scale and be a durable finish if you use a self etching primer?
Reply:HA~!!!  I'm so tough I remove millscale with my TEETH~!! Hey~!! It's a hobby. It's not supposed to make sense~!!
Reply:A good example of mill scale. These are the gussets for the fork lift carriage project.http://weldingweb.com/vbb/showthread.php?t=280591 This was really heavy mill scale and very tough to cut through. Once you're through the mill scale, the steel was easy to bevel.BTW, I beveled these with a tiger paw. I really need to start using these more often. The good ones work fantastic. I couldn't believe how fast I could cut this bevel."Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"