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  • Backgassing SS seam

    I need to weld some pieces of 17ga 304 together. The longest seam will probably be about 12" long. Other spots will be pretty small. What's the best way to back gas this? I am thinking of laying a couple pieces of angle on the bench to make a small channel to lay the SS on top of. Then flow Ar in one end. Does that sound workable? The only problem I see with this is it will make it difficult to clamp the pieces together.

    Later, maybe I'll do enough to justify the expense of the Solarflux or some such stuff, but right now that isn't the case.

    Dave
    Still building my new old truck - see the progress!
    http://www.ford-trucks.com/forums/65...-coe-idea.html
    http://www.hobartwelders.com/weldtal...ad.php?t=27017

    Square Wave TIG 200 - Woot!
    MM180
    SP125+

  • #2
    I think that you're on the right track, but like you said, you might have trouble clamping. What if you took two pieces of plate (say 1 square foot each) and put them on your bench with a gap in between them. Then put your pieces on the plate with the gap lined up over the seam. You could then back-gas the seam. You might even be able to do it with a couple of pieces of damp plywood?

    Do you have a spare argon tank and regulator to back-gas with?
    Miller Dynasty 200DX
    Hobart T225 Stick
    Hobart Handler 180
    Airco O/A Rig
    ESAB W-200 O/A torch

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    • #3
      Thanks! I saw where somebody mentioned blocking off the backside with a piece of copper also. I had a couple of nuts to weld so on the bolt side, I used a zinc plated washer. That doesn't work. It almost looks like the zinc vaporizes and bubbles up into the molten SS above it. Copper may have done okay, but I don't know where my little piece that I use for backing has disappeared to. It's under the mess somewhere, though.

      Anyway, I don't have a second bottle, so that was going to be a bit tricky. I could plumb in a second line from the flowmeter, but the hard part is regulating it. I kinda thought of putting a valve at the bench to turn on and off the back gassing, but I'd have no idea how much of the flow was going to the back and how much was coming out the torch. I do have an 80CF bottle that is empty, so maybe I'll go get it filled and use it. That would probably be easiest, since I do have another flowmeter that I can use.

      Dave
      Still building my new old truck - see the progress!
      http://www.ford-trucks.com/forums/65...-coe-idea.html
      http://www.hobartwelders.com/weldtal...ad.php?t=27017

      Square Wave TIG 200 - Woot!
      MM180
      SP125+

      Comment


      • #4
        I could be wrong, but don't think that a copper backing strip would replace back purging for this operation. Your SS sheet is too thin.

        If you have another regulator then you should look into getting a Western 401 "Y" adapter. It would let you run two regulators off of one tank. See attached pic...
        Miller Dynasty 200DX
        Hobart T225 Stick
        Hobart Handler 180
        Airco O/A Rig
        ESAB W-200 O/A torch

        Comment


        • #5
          Originally posted by villemur View Post
          I could be wrong, but don't think that a copper backing strip would replace back purging for this operation. Your SS sheet is too thin.

          If you have another regulator then you should look into getting a Western 401 "Y" adapter. It would let you run two regulators off of one tank. See attached pic...
          The Y will work great. Just buy a inexpensive HTP $30 regulator and a hose and your set. A dual regulator will run you $240-$340. Not worth it unless you do this everyday and want to be the cool guy with all the new toys.

          HTP regulator:
          http://cgi.ebay.com/Argon-CO2-Flowme...3286.m14.l1318

          Dual regulator:
          http://store.cyberweld.com/viredfm150du.html
          ^ cheapest I found. Air gas was the highest

          James
          Last edited by StillBoostin; 07-17-2008, 11:02 PM.
          Miller Dynasty 200DX
          Weld Tec water cooler
          Miller Millermatic 180 w/ Spoolmate 100
          20 Ton press
          Lots of tools

          To some racing is for fun. Others it's a way of Life.

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          • #6
            Well, for lack of a "Y" to allow the use of 2 regs, I tried a single reg last night with a "T" in the line downstream. Then I zip-tied a ball valve to the bench leg. I ran the flowmeter up to almost 30 cfh (max is 30) and opened the ball valve enough to have detectable flow that seemed about the same from both my back-gassing line and the torch. Of course, when the valve in the welder is closed, I get 30 cfh in the back and then while welding it's split. I didn't do the flat pieces last night, but I did use it to purge a section of tail-pipe, and it worked. If I don't end up doing much SS, I may just use this setup. It at least gets me by. Otherwise, that "Y" may be the way to go. Or maybe I'll still get another bottle of Ar. And I may go ahead and get another reg so I don't have to move one of them.

            Thanks all!
            Dave
            Still building my new old truck - see the progress!
            http://www.ford-trucks.com/forums/65...-coe-idea.html
            http://www.hobartwelders.com/weldtal...ad.php?t=27017

            Square Wave TIG 200 - Woot!
            MM180
            SP125+

            Comment


            • #7
              Aluminum tape is good to use for back gassing, too..it cam form to irregular surfaces.

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              • #8
                aluminum tape - hmmm

                I thought that I had read that before somewhere. What happens to the adhesive when it gets hot? Or am I thinking of something else?

                Dave
                Still building my new old truck - see the progress!
                http://www.ford-trucks.com/forums/65...-coe-idea.html
                http://www.hobartwelders.com/weldtal...ad.php?t=27017

                Square Wave TIG 200 - Woot!
                MM180
                SP125+

                Comment


                • #9
                  BTW, I did have a couple of spots I needed just a little bit of protection on the backside for, so I found my little bit of flattened copper pipe and clamped it along with the two pieces to be joined. It actually did quite nicely. In fact, I'm not so sure that the back side didn't look better than the front.

                  Dave
                  Still building my new old truck - see the progress!
                  http://www.ford-trucks.com/forums/65...-coe-idea.html
                  http://www.hobartwelders.com/weldtal...ad.php?t=27017

                  Square Wave TIG 200 - Woot!
                  MM180
                  SP125+

                  Comment


                  • #10
                    Originally posted by whateg0 View Post
                    I thought that I had read that before somewhere. What happens to the adhesive when it gets hot? Or am I thinking of something else?

                    Dave
                    Yeah, when the glue gets hot, it lets go, ...ya just hafta take that into consideration when you tape it up.

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