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  • Mil scale removal

    What’s everyone’s preferred method to remove mil scale before welding? My preferred as of now is patience with a flap wheel in areas to be welded.

  • #2
    Flap wheels maybe a little on the less aggressive side of things......I grinder with a 80 grit works. Personally anymore when I'm fabing nice things in basic steel I use nothing but cold-rolled.....wash it with brake fluid, wipe it with some acetone and it's ready for a TIG , MIG or arc.

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    • #3
      https://www.thefabricator.com/thefab...ove-mill-scale

      These seem to be considered the greatest thing since sliced bread.

      Pferd isn't the only maker of diamond coated brushes.

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      • #4
        The flap disc works ok, but if you’re doing a lot or your metal has a heavy mill scale, the flap disc will load up and not cut as well. Then you’ll be putting a ton of pressure on it and just burnish over the mill scale. A hard rock is so much faster and doesn’t load up, it’s just a lot more clean up with finer grits if you get carried away. For light mill scale, on say 2” tubing for example, I’ve found the paint stripping wheels for a 4 1/2” grinder work exceptionally well. You just have to be careful not to hang the edge of the metal on the wheel because it will tear a big chunk out of you $11 fancy paint stripping abrasive.

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        • #5
          Originally posted by ryanjones2150 View Post
          I’ve found the paint stripping wheels for a 4 1/2” grinder work exceptionally well. You just have to be careful not to hang the edge of the metal on the wheel because it will tear a big chunk out of you $11 fancy paint stripping abrasive.
          They do work well, wish they lasted longer though
          Richard
          West coast of Florida

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          • #6
            I usually use a knotted wire cup brush in my 4.5" grinder. I heard the paint stripping discs worked pretty well, so I got a Warrior brand polycarbide disc from harbor freight to try. Cost about 5 bucks and worked pretty well, but as previously mentioned, doesn't last very long and be real careful around the edges. I used it to remove all the mill scale from 4 6"x 13" plates. HF also has smaller ones that will work in a drill.

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            • #7
              When i worked in the big factory all of our mill scale had to be ground 1" on either side of the weld area. Angle grinder and grinding wheel was the best...Bob
              Bob Wright

              Spool Gun conversion. How To Do It. Below.
              http://www.millerwelds.com/resources...php?albumid=48

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              • #8
                I use a depressed center grinding disks. The ones with the 5/8 nut made in the disk lay it down almost flat till I see shiny steel then lay it flat and flush grind. You dont gouge the material that way. Then flush it with a 60 grit flap disc .
                Dynasty 400 wireless
                Coolmate 3.5
                Sw320 speedway
                Ck flex lock 230
                4 victor flow meters
                2 Flametech Duel flowmeters
                2 genuine miller torch buttons
                A$$ loads of tungsten
                XMT 350 CC/CV
                S74DX feeder
                Stick leads from here to China
                A30 Spool gun
                WC24
                Langmuir crossfire hobby table
                Everlast powerplasma 100 w hypertherm torch
                Harris O/A
                Pet raccoon
                I'm just a peckerwood in the boonies with fancy welding equipment

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                • #9
                  I found this porosity test pic I did on unground HR with 7018, it had no problem at all going through mill scale, the pass was made with my 110 volt stick machine.

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                  • #10
                    Stick welding is the least effected by mill scale of all the arc welding processes. If I’m stick welding, I almost never even bother with the mill scale.

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                    • #11
                      I think on most steel a grinding wheel works best/fastest. Flap wheels seem to dull up and take longer. On thick plate where the end finish is not so important and heavy scale is encountered, a needle scaler or chipping gun may work best.
                      MM250
                      Trailblazer 250g
                      22a feeder
                      Lincoln ac/dc 225
                      Victor O/A
                      MM200 black face
                      Whitney 30 ton hydraulic punch
                      Lown 1/8x 36" power roller
                      Arco roto-phase model M
                      Vectrax 7x12 band saw
                      Miller spectrum 875
                      30a spoolgun w/wc-24
                      Syncrowave 250
                      RCCS-14

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                      • #12
                        I have boxes of different grit 3" roloc sanding dics that work great for me.. I would imagine they make them for all sizes of grinders, but you would need to buy a rubber backing pad also.

                        https://www.amazon.com/3M-01397-Gree...4X4QNTFBSNEQMD

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                        • #13
                          Some reading on mill scale indicates it's essentially a form of rust.
                          Both LinKoon and Esab say removal down to ****** steel isn't necessary and both tout wires that claim to have no problem welding thru thin scale. Both also say slightly higher quantities of Silica and Manganese make it happen and e**-s6 wire contains sufficiency of both elements where the s3 wires don't.

                          We pretty much know burning thru scale isn't a problem with stick.

                          Having seen the new superlazer removsall video and having long ago used a flame scraper to pop rust and scale, I find myself wondering what if a carbon arc or even tungsten in a TIG torch was used to apply a generous dose of hot to the scale followed by a wire brush or scraper? I'm pondering on AC arc with a round pointed carbon in the TIG torch to produce a wide arc rather than a concentrated arc. Maybe I'll hunt up a hunk of scaled steel and try the idea right after I find some ambition.

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                          • #14
                            https://www.youtube.com/watch?v=ACGSzBXKONo

                            I think this is the next generation of tooling to remove rust and mill scale. I asked and I couldn't afford it.

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                            • #15
                              Originally posted by Noel View Post
                              https://www.youtube.com/watch?v=ACGSzBXKONo

                              I think this is the next generation of tooling to remove rust and mill scale. I asked and I couldn't afford it.
                              Likelihood of that toy arriving in the shop via Horrible Fright or Princess Auto is pretty low in my estimation.

                              There may also be a way of popping or disassembling slag employing the process often misidentified as electrolysis which is actually a form of electroplating.

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