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Backup gas for Stainless

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  • Backup gas for Stainless

    I was asked to repair a piece of stainless trim for a guys hotrod yesterday. It was really thin. Someone had tried to mig it and butchered it. I cut out the damage and put in a patch. It worked out good. I did not use any backup gas though and the underside of the piece did'nt look so good. I need to find some backup gas plates. They don't seem to be easy to find. I called Indiana Ox. no luck, No luck on e-bay. If anyone knows where to buy some let me know. I may just make some.

    Monte, I don't know if this will help your shiny/dull question but something I have started doing that seems to help is to make a quick lower current pass over the first couple of inches that I am going to weld. It seems to do two things. Preclean and preheat. Then back to the start and punch the pedal. The best welds that I get seem to be the ones where a good puddle forms quickly. Works for me anyways, Adam
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  • #2
    Jet,

    What you're experiencing on the backside of the weld is called "sugaring". Very common when welding thinner SS.

    You're making too much of what constitutes a "backing plate". Basically all you need to do is create a "gas dam" for your purge gas (generally Ar). It can be fabricated from nearly anything. I have used sheet copper or aluminum flashing to create a gas pocket on the backside of the weld. Alum flashing works well, is cheap, and is easy to conform to the shape you need.

    You will need a second bottle of Ar and a separate regulator (or one of the dual output flowmeters).
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    • #3
      dose it have to be argon as a backer or could you get away with strait Co2 ? if your argon spair runs out and Co2 is all ya have on hand use it or wait till you get more argon ?
      thanks for the help
      ......or..........
      hope i helped
      sigpic
      feel free to shoot me an e-mail direct i have time to chat. james@newyorkmetalart.com
      summer is here, plant a tree. if you don't have space or time to plant one sponsor some one else to plant one for you. a tree is an investment in our planet, help it out.
      JAMES

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      • #4
        100% CO2 is the LAST thing you want around a SS weld.

        You want your purging gas to be an inert gas. CO2 is a "reactive" gas.

        Although CO2 is used in very small quantities in tri-mix (2 1/2%) it is definitely not recommended for a purging gas for SS.
        Syncrowave 250 DX Tigrunner
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        Milwaukee 8" Metal Cut Saw, Milwaukee Portaband.
        Thermco and Smith (2) Gas Mixers
        More grinders than hands

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        • #5
          What about using a flux on the back side like Solar Flux instead of messing with the gas? Wouldn't that be much easier?

          Craig

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          • #6
            Originally posted by SundownIII View Post
            100% CO2 is the LAST thing you want around a SS weld.

            You want your purging gas to be an inert gas. CO2 is a "reactive" gas.

            Although CO2 is used in very small quantities in tri-mix (2 1/2%) it is definitely not recommended for a purging gas for SS.

            On tig

            Forney mig wire even says co2 on 308L wire right on the box (100%) ...or at least they used to... so I tried it one day and it worked just fine. Not saying it's the best by any means but they said it and I did it.

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            • #7
              i thought the pass port used Co2 for stainless, thats why i thought maybe it could be used as a back gas when TIGing.

              as for holding the back gas in place i have used tin foil taped to the back to make a chamber around the back of the weld. maybe not the best option, but it worked.
              thanks for the help
              ......or..........
              hope i helped
              sigpic
              feel free to shoot me an e-mail direct i have time to chat. james@newyorkmetalart.com
              summer is here, plant a tree. if you don't have space or time to plant one sponsor some one else to plant one for you. a tree is an investment in our planet, help it out.
              JAMES

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              • #8
                On little jobs I use this http://www.weldhugger.com/ but sometimes you have to make your own. They aren't cheap but pretty universal. Backshield with argon

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                • #9
                  Dang BVWELD,

                  Neat little tool, but they are mighty proud of them.

                  I can buy a lot of aluminum flashing and duct tape for those prices.

                  Thanks for posting though.
                  Syncrowave 250 DX Tigrunner
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                  Miller XMT 304 w/714D Feeder & Optima Control
                  Miller MM 251 w/Q300 & 30A SG
                  Hobart HH187
                  Dialarc 250 AC/DC
                  Hypertherm PM 600 & 1250
                  Wilton 7"x12" bandsaw
                  PC Dry Cut Saw, Dewalt Chop Saw
                  Milwaukee 8" Metal Cut Saw, Milwaukee Portaband.
                  Thermco and Smith (2) Gas Mixers
                  More grinders than hands

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                  • #10
                    Originally posted by SundownIII View Post
                    Dang BVWELD,

                    Neat little tool, but they are mighty proud of them.

                    I can buy a lot of aluminum flashing and duct tape for those prices.

                    Thanks for posting though.
                    Don't forget the Reynolds Wrap You think thats high, price purge bladders

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                    • #11
                      bvweld, i have seen them before but always thought of them as trailing shields. may be worth the $$ for some of the more exotic metals, but for most back gas i think you would need a production run to justify the $.
                      although to each his own, it is a cool setup with lots of options.
                      thanks for the help
                      ......or..........
                      hope i helped
                      sigpic
                      feel free to shoot me an e-mail direct i have time to chat. james@newyorkmetalart.com
                      summer is here, plant a tree. if you don't have space or time to plant one sponsor some one else to plant one for you. a tree is an investment in our planet, help it out.
                      JAMES

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                      • #12
                        Originally posted by fun4now View Post
                        bvweld, i have seen them before but always thought of them as trailing shields. may be worth the $$ for some of the more exotic metals, but for most back gas i think you would need a production run to justify the $.
                        although to each his own, it is a cool setup with lots of options.
                        Looks like they have gone up since I bought mine. I used to work in an engineering design group and frequently had special needs and time is money. I still use low buck methods when it's just a job or two,what ever it takes to "GET R DONE". Trailing shields generally clamp on the torch. Titanium requires this along with backing unless you are in a "tent". I don't think there is anything cheap in regards to welding especially if they think your making money with it.

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                        • #13
                          Back up gas for Stainless

                          You definetly you want to use staright Argon for your inner shield gas. This helps keep your weld in a clean enviroment. Make some end caps out of Aluminum foil thats the cheapest way. Put a 1/4 hole in one end to let the purge come out . Set the purge aroung 20-25 psi this will give you a nice clean weld and there will not be a sugar . Sugar on stainless is not good it can cause a bad weld and itsn't going to stand any pressure at all. I weld stainless for a living in the cryogenic and bio industry. Try this ! this should solve any problems of sugaring. What every you do don't use anything other then Argon!!!! Hope this is helpful

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                          • #14
                            I have used speed tape which is basically soft alluminum that is adhesive backed. I form the enclosure with the tape, alluminum foil works great too (i might suggest the heavier one like they sell at costco). I use a piece of gas welding hose with some soft copper tubing stuffed in the end so it can handle high heat, although not the best way to do it you could split the flow going to the torch and use only one regulator, but for 20 bucks you could get the western T and use a spare flow gauge. I have 2 HTP flow meters (45 bucks each on ebay) with the T. I have a valve in the backpurge line so i can turn it on and off easily. I you make your enclosure very tight you will need to make a bleed hole on the other end. I have sucessfully welded stainless with the back purge enclosure open on top (argon is heavier then air). I also use a BBQ lighter to check for lack of 02 (ghetto, but cheap and effective in my experience). Whatever you do be sure to test it first!!
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                            • #15
                              Set the purge aroung 20-25 psi this will give you a nice clean weld and there will not be a sugar .

                              I was watching a demo for SS welding and watched other friends do it also, 5-10psi was fine for purging after a few seconds of filling up the "chamber".
                              No sugar and welds were beautiful!!! 20-25psi is just wasting argon.
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