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welding Mild steel to Chromemolly roll cage

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  • welding Mild steel to Chromemolly roll cage

    Got a question for you all.
    My buddy has a race car that's an older build and we are adding some extra bracing to the roll cage with mild steel 1-5/8 tubing. We are pretty sure the cage is also mild steel, but if it were chromolly, would there any trouble in MIG welding the mild steel bracing to the chromolly, any special procedures before welding ? I have a millermatic 211 with 70s-6 .035 wire, would that be suffice ?
    And any tips on how we can tell if the original cage is mild steel or chromolly ?
    thanks for any help you guys can provide.
    SyncrowaveŽ 200
    Lincoln AC/DC 225/125
    Lincoln Weld Pak 100 wire feed

  • #2
    I'm no expert, but just about the only thing I would do is make sure the shop ambient temperature was at least 70°F. I would also make sure there are zero drafts that would aid in increasing the cooling rate of the joint.

    Many chromoly tubes are labeled just that "4130 Chromoly-N", for those that are in the normalized condition. Is the cage painted?
    Last edited by OscarJr; 03-08-2016, 12:14 PM.
    HTP Invertig221 D.V. Water-cooled
    Eastwood MIG175 w/spoolgun
    Eastwood Versacut40 Plasma cutter

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    • #3
      If you're worried about it cooling too fast, just hit it with a torch before and after. I've welded plenty of 4130 to mild steel for drag car stuff. I'm not really the expert or anything, especially since we use whatever we can get our hands on to build the garbage we race and we're "roadkill approved" I might add. Ask Freiburger about it, he'll vouch for me. <br />
      <br />
      But, if you really are concerned about it, give it some preheat and tig it with er80sd2, which is my process of choice for roll cages. But if it was me, I'd probably just roll with what I had.

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      • #4
        Thanks guys.. after looking at some pics of the installed roll bar, the welded joints are definitely mig welded and we are now 99% sure the cage is mild steel, so the supports we're adding which are also mild steel will get mig welded.. wish i could get my tig machine to his shop, but mig it is.. thanks again
        SyncrowaveŽ 200
        Lincoln AC/DC 225/125
        Lincoln Weld Pak 100 wire feed

        Comment


        • #5
          Roll cage??? I Got a 46 willys jeep with just a rusty windshield frame and a boosted lt4 and t56. Looks like I gotta get on board with one of those...probably going to weld 4130 directly to my frame...got pIles of 4130 and been welding to mild for long time on many projects...only 1 failure but thats a whole different story... i weld about as good as I drive if that means anything
          blue stock,
          miller shopmaster 300, s22a feeder, s30 spool gun, hf251, arc pig
          miller maxstar 150 STL
          miller maxstar 210
          miller a bp 330
          non blue,
          Lincoln weldanpower 150 1982 model
          esab plasma
          Hobart ironman 210, spool gun
          victor oxy acy set
          thousands of snap on tools, 3 large boxes and tons of automotive equip.

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          • #6
            Well, are you a good driver?

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            • #7
              See me standing in my old zookie...good enough for most maneuvers but have the occasional back fire from time to time
              blue stock,
              miller shopmaster 300, s22a feeder, s30 spool gun, hf251, arc pig
              miller maxstar 150 STL
              miller maxstar 210
              miller a bp 330
              non blue,
              Lincoln weldanpower 150 1982 model
              esab plasma
              Hobart ironman 210, spool gun
              victor oxy acy set
              thousands of snap on tools, 3 large boxes and tons of automotive equip.

              Comment


              • #8
                Quite often to be honest...
                blue stock,
                miller shopmaster 300, s22a feeder, s30 spool gun, hf251, arc pig
                miller maxstar 150 STL
                miller maxstar 210
                miller a bp 330
                non blue,
                Lincoln weldanpower 150 1982 model
                esab plasma
                Hobart ironman 210, spool gun
                victor oxy acy set
                thousands of snap on tools, 3 large boxes and tons of automotive equip.

                Comment


                • #9
                  Not meaning to hi-jack this thread,but sense were on this subject of molly/mild steel.I need to weld a molly steering joint to a mil steel shaft.What gas/wire will this require?...........Thaxs

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                  • #10
                    If it's steering I'd probably tig with pre and post heat..I do mig it all the time but on less important systems than steering. No problem with mig, I use 030 and 035 wire mostly. As for gas I just use 75 25 mix on the mig...pure argon on tig.
                    Shaft from column to box/rack or from unit to wheel knuckle? Forces are much lower on the column shaft so I wouldn't be afraid either way
                    blue stock,
                    miller shopmaster 300, s22a feeder, s30 spool gun, hf251, arc pig
                    miller maxstar 150 STL
                    miller maxstar 210
                    miller a bp 330
                    non blue,
                    Lincoln weldanpower 150 1982 model
                    esab plasma
                    Hobart ironman 210, spool gun
                    victor oxy acy set
                    thousands of snap on tools, 3 large boxes and tons of automotive equip.

                    Comment


                    • #11
                      Don't sweat it, not nearly as life changing as it sounds. Chromoly and mild steel are successfully welded all the time. The smaller the pieces, the less likely you'll need any pre or post heat. I'd say tig it for sure and take your time. The reason for pre and post heat is so it doesn't cool too rapidly. If the parts are small, it will most likely heat up the rest of the part away from the weldment that it won't be an issue. You can use whatever mild steel tig wire you have and pure argon. I have never migged chromoly to mild steel, but I'd imagine it's the same deal for that, normal mild steel wire and the appropriate gas for that wire.

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                      • #12
                        Thaxs fellas got to refill the bottles tomorrow and get some wire from the supply store anyway, I have the small bottle for argon think i'm going to get a bigger bottle that little bottle does not last long.........Thaxs

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                        • #13
                          Originally posted by ryanjones2150 View Post
                          Don't sweat it, not nearly as life changing as it sounds. Chromoly and mild steel are successfully welded all the time. The smaller the pieces, the less likely you'll need any pre or post heat. I'd say tig it for sure and take your time. The reason for pre and post heat is so it doesn't cool too rapidly. If the parts are small, it will most likely heat up the rest of the part away from the weldment that it won't be an issue. You can use whatever mild steel tig wire you have and pure argon. I have never migged chromoly to mild steel, but I'd imagine it's the same deal for that, normal mild steel wire and the appropriate gas for that wire.
                          I have actually flux core some molly/ms before(it's all I had at the time)and it held up fine.As a matter of fact this is the joint that's getting cut off and re-welded due to the new rack system being installed.

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                          • #14
                            Kind of figured there wouldn't be much difference.

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                            • #15
                              Tig it real nice then melt some brazing rod on it and tell your buddies you brazed it...see how many are willing to ride with you.
                              blue stock,
                              miller shopmaster 300, s22a feeder, s30 spool gun, hf251, arc pig
                              miller maxstar 150 STL
                              miller maxstar 210
                              miller a bp 330
                              non blue,
                              Lincoln weldanpower 150 1982 model
                              esab plasma
                              Hobart ironman 210, spool gun
                              victor oxy acy set
                              thousands of snap on tools, 3 large boxes and tons of automotive equip.

                              Comment

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