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  • tig stainless ,,frosting

    when i tig stainless ,1-16 th ,,i can tig it just fine
    i can control heat, fine with foot peddle,,
    flow is at 20,,,i can lay down a nice weld.
    weld looks just fine,, all positions ,,on the top
    tigging 316 ,,,useing 3/32 tung ,, 316, tig rod

    BUT the back side of the weld looks like crap
    looks like burnt toast ,,,what the is going on ,,
    should i change to smaller tungsten;,,and rod size,,,
    staying to long in that area ,,should i move faster
    or is it just dificult to tig,, any tips ,, thanks,,,,

    bill

  • #2
    Back Purge

    You have to back purge stainless what your seeing is sugar and sugar is contamination.you need an inert gas coverage on the back preferably argon.

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    • #3
      back purge

      so all stainless has to be purged..
      we had some 316 weld at a shop useing tig ,,pipe 3/16,,,
      he didn't purge the pipe ;;

      so ,it would have the same look inside if it were to cut open...sugaring or that burnt look,, it is used for salt water at maby ,,2 psi,,but the water would hammer at the frosting ,and create air bubbles ;;;;no
      why didn't they purge,, is it cause of the thickness of the pipe,,does thi matter for purgeing
      i was looking for some pic's on the site ,but no luck ,,,thanks

      bill

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      • #4
        Go to the search topic, there has been a lot said about Stainless and back purge. John
        Long time Teacher - Processes
        Owner - 2 LWS's
        Hobart - Lincoln- Miller - ESAB(Linde)

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        • #5
          Thanks john


          bill

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          • #6
            Backpurge or Solarflux are the two principle options.
            I may not be good looking, but I make up for it with my dazzling lack of personality

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            • #7
              ok ;;purging ,,now make's sense,half to do it to get 100% weld ,,,
              never herd of this ....solar flux.. ,,can you give some detail, on this product
              thanks


              bill

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              • #8
                Bill, it's Solar B flux. It comes in a powder, you mix it with denatured alcohol, paint it on, and wait for the alcohol to evaporate..it work great for inside of something you can't purge with argon...but it is terrible to remove after.

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                • #9
                  What 'sugar' is in essence is what is called 'carburization'. In the presence of oxygen at critical temperature the carbon content in the stainless effectively boils out and oxidizes instantly causing 'sugar', 'berries', "pi$$ poor welding' or what ever the local slang term is, that 'sugar' is carbon. Where this has been allowed to occur, the general consensus is the the weld is less than 20% as strong as it could be, will be extremely susceptable to chemical and salt attack and don't even let a USDA inspector find one weld like this in a dairy plant unless you want to cut 5 or 10 more joints for him/her to look at. I have in some cases where back gassing wasn't practical, even used a sheet of copper clamped against the back of the weld. Copper and stainless really hate each other especially at or above critical temperature, so the weld is sheilded from O2 with no metal transfer. This is one of the slickest ways I've found to weld a handle back on a Revereware pot short of spot welding. STAINLESS MUST BE BACK SHIELDED!!
                  Not back gassing is a VERY costly mistake inlight of the simplicity of doing it correctly. Especially working with 316 stainless.

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                  • #10
                    So Solarflux B works good. How do you remove the remains??? I have some very thin wall fabrications that I make. Essentially rectangular tubes made up of 4 flats. Can I blow glass beads down the finished tubes?? It would be nicer to use some kind of liquid bath. These parts you can hold in your hand (when cooled haha), you just can't get at the inside.

                    These fabrications are made from 304 SS .018 thick. I have a double regulator that I use to back purge and some copper alignment blocks that are tapped for hose fittings so I do back purge but it uses a lot of gas for the job.

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                    • #11
                      From the Solar B flux website:
                      The thin glass-like residue is chemically inert after welding and adheres tenaciously to the base metal. While this residue is unattractive to the eye, it does not affect the quality of the weld and usually need not be removed. However, if removal is desired, it is easily accomplished with a stainless steel wheel, stainless steel brush or common pickling compounds. Our research indicates that 'Wonder Gel', manufactured by Bradford DeRustIt Company is excellent.

                      (Note: there are some pipe or tube welding applications where absolute purity and a polished inside surface are required. These include food or beverage lines where subsequent product refining will not take place, medical oxygen lines, computer chip manufacturing air lines, and high service temperature (above 1000°F) steam lines. In these situations we recommend purging instead of SOLAR FLUX so as to avoid a difficult chemical cleaning process.

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                      • #12
                        One thing. If you do use Solar Flux Make sure to clean it off the faces of the weld area. If not it will migrate to the surface and will be a "B" to get off. It works it way along the edges of the bead.
                        With it only on the back side it is not a problem. I found this the hard way. It is easier than purging a strange shape. I mostly do exhaust systems and it works very well for that.

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