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Help with full penetration on 12ga.

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  • Help with full penetration on 12ga.

    I don't know if this is the correct spot for this but I'll try anyway. I work in a pipe/sheet metal fabrication shop. We have some 12ga galv sheet metal that they want welded up with full penetration. They told me to try GMAW which didn't pen at all, 70s hard wire. Then I tried GTAW and that broke it down but what mess. Any suggestion's would be great. Thanks

  • #2
    I do not think you are going to get a successful weld using Tig on that galvanized material. The zinc is going to smoke like crazy and foul the weld.
    If it were me I would grind off all of the galvanized material in the area of the weld, then weld it using Tig.
    The powers that be may want it completely galvanized, but that is not going to happen unless they send it out to be re-dipped after welding is complete.
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    • #3
      They said I could grind down where the galvanized is at. So I'll try on a scrap piece tomorrow. Any other good way of getting full pen with a different type of procedure?

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      • #4
        You could try flux cored wire .They have wire for coated steels.

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        • #5
          I just got done making some full pen welds on some galvanized I-beam for an overhead trolley in my shop. Depending on how thick that coating is, it can be very hard to get it all off. You might think you have it all off, but when you weld, you'll see boiling out of there.

          Generally, when I weld on galvanized stuff, I prefer to stick weld it. 6010 will cut right through it and send off all sorts of awesome stuff that you shouldn't breathe in. Which is another reason why I use a stick rod, I can ramp up the ventilation fan and have another blowing right on me to get those nasty fumes away.

          But still drink milk and wear a respiratory. Miller makes a really low profile one that claims to filter out not just the zinc oxide, but hexavalent chromium as well when welding stainless. It was worth the $40 or however much it cost.

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          • #6
            I tried hard wire but that was a waste of time. Wouldn't 6010 be a little much for 12ga galv? I'm a pipe welder by trade, so I'm familiar with 6010. Guess it would have to 3/32 rods... And heat super low. Their making it known "got to have full pen!!!"

            And yes a respirator is a must for any welding!!! I also have a Miller fresh air sheild, works great but after a 8-10 hr day its alittle hard on the neck. Respirator and a fan do well. Thanks

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            • #7
              I've never tried it, but maybe flux core or some dual shield wire might be an option. I would guess it would certainly be better than solid wire.

              How long are the welds?

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              • #8
                That's how the duct welder's do it. The use flux core or core sheild. One of the two. That stuff sucks anyway. I hate welding duct!!! But anyway, I don't think I'm going to get the penetration they want with mig. Its going to be butt seams.
                I'm not sure how long the welds are other then it's 30" round 12ga, and some square to rounds. The round stuff is probably 4'-6' tall with a seam all way down.

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                • #9
                  No mig,no tig ,no stick,no flux cored.About the only thing left is grind off galv.and OA weld it.

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                  • #10
                    Wonder how'd that would work out?

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                    • #11
                      Braze it.

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                      • #12
                        Wonder if I pulsed Tig it would it work better? The machine is a XMT 304. So they would have to rent or buy a pulse control for it.

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                        • #13
                          Pulsed Tig is not going to make any difference at all.
                          What you are fighting is the zinc coating on the 12ga steel. That crap boils and then fouls the weld.

                          Take a piece of 12ga bare steel and it will weld with complete fusion as easy as drawing a line.
                          Galvanized is never going to be weldable with the Tig process in my opinion.
                          And like others have said.....Those zinc fumes will make you very sick. Your boss needs to be told this.
                          Dynasty 200 DX_set up on 3 phase
                          Coolmate 3
                          MM 251 w/ Spoolmatic 30A
                          HTP 625 Micro Cut Plasma Cutter
                          Victor O/A Rig
                          Bridgeport Mill_3 phase (w/ Acu-Rite 4 axis DRO)
                          10 inch South Bend Lathe_3 phase
                          Baldor Double Cup Tool Grinder_3 phase
                          Baldor 10 inch Buffer
                          Rockwell 12 inch Disc Sander
                          Cyclone 2ft X 3ft Bead Blast Cabinet
                          Quincy 325 2stg- Air Compressor_3 phase
                          Graymills Built-in Parts Washer
                          Rockwell/Delta Planer, HD Shaper, Uni-Saw etc.

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                          • #14
                            I agree with piniongear. Even when I attempt to tig after grinding off the zinc, I always end up finding a place with some of the foul stuff left. It's really easy I think you've ground enough off and just burnished it back a little. I am not very experienced with O&A outside of cutting and a little brazing, but could be a solution I guess. I'm still leaning towards stick. Any way you can get some test pieces and work through a welding process ahead of time? Good luck my friend. Let us know what you work out.

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                            • #15
                              Originally posted by BOBBYLEE View Post
                              We have some 12ga galv sheet metal that they want welded up with full penetration. They told me to try GMAW which didn't pen at all, 70s hard wire. Then I tried GTAW and that broke it down but what mess. Any suggestion's would be great. Thanks
                              I was a union sheet metal welder for 8 years. The only way you are going to get full pen is either gap the parts or bevel the edges. Then weld away with a mig and .030 wire. No problem...Bob
                              Bob Wright

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