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Thread: Tig Welding 20 Gauge Stainless Steel

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    Tig Welding 20 Gauge Stainless Steel

    Made a frustum out of 20 gauge stainless steel. Have never welded anything this thin before.
    Anyway... got it done, however I'm thinking there must be a better way. Any tips or constructive critique would be greatly appreciated.

    Fusion welded lap joints. Everlast 255EXT at 30 amps, 3/32" lanthanated tungsten, 15 cfh, and # 5 glass nozzle. Preflow .5 second. Postflow 5 seconds. Using 308 filler just burned holes in the material by the time I got the filler to melt. Later, got to thinking spot welding might be the way to go although I am not familiar with the technique for thin metal.




    I'm an off-roader and when in doubt, build it stout type. So thin material is rather new to me.
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    Last edited by robert-r; 07-21-2020 at 06:01 PM.
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    Re: Tig Welding 20 Gauge Stainless Steel

    Do you have a copper chill bar that you can clamp to the back? Might want to turn up the heat a little bit and move faster.
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    Re: Tig Welding 20 Gauge Stainless Steel

    As stated a copper backing bar, aluminum works well too. You don't say what diameter filler but fusion is a good way
    to go. Also a high speed pulse would help in this situation.

    Looks like you got it done and if it performs as you want then good to go.
    Richard
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    Re: Tig Welding 20 Gauge Stainless Steel

    This stuff works better with back purge.
    I you have a way to clamp it together, run a strip of what you got for light sheet metal on the back side 4" wide. Tape it in place with foil tape. Run a hose from a flow meter into the bottom. Close around it with whatever. Leave a little gap at top for air to escape.

    I'd bet you'll be happier with a small filler. 1/16 or smaller.

    Err on the side of too hot, move along quickly.
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    Re: Tig Welding 20 Gauge Stainless Steel

    robert-r,
    I'm not an SS expert with tons of experience. But one method I've used to weld thinner SS is a combination of eliminating the back weld area's exposure to air - without purge, and 2nd adding chill blocks to the sides of the welds to help keep the net heat added to the puddle area 'cooler'.

    To do that in this case (shown in pics) I'd suggest a flat bar of 1" x 1/4" or heavier directly behind and evenly centered on the joint- if.... the 1" width flattens the joint tooo much due to the arc of the conic section? Then narrow the flat bar until the most surface of the flat bar is against the joint's back area. This both acts as a chill bar AND excludes weld bulge through (penetration) that can 'sugar'. The chill block allows the weld to stop at the surface of the parent metal's joint edges.

    Second set of chill blocks is a set of bars- rounded or beveled one one long edge. These would be lined up one both sides of the weld about 1/4" or less from both sides of the edges of the cone's end cuts.

    They can help with several aspects of a weld like this.

    One, the chill bars act as set of guides so you could adjust the tungsten to gas cup stick out so there's a 'drag/walk/guide' the cup relationship to the weld joint?

    Two, the aluminum bars being rounded or beveled (like the cut off edge of a typical 6061-T6 3/8" x 1- 1/2" angle extrusion) help form a tapered gas cup trough to enhance the guide like aspect of the two bars. Where a fixed 90 isn't quite as helpful in this manner because of various torch angles moving the tungsten to work distance and travel angel much more than happens when the gas cup is in a tapered groove.

    To make #2 into a more clear (verbal/text) picture for your consideration? You can take your torch and mock up both a square edge set of chill blocks and a tapered or bull nosed- round over edged set of blocks - and then mock the weld (torch off) and observe the differences in results of movements on tungsten to work position?

    Third, like all chill blocks, including using the backing block- your weld can be slightly slower without overheating the SS. And the result of slower travel speed is more control of the weld shape as moving fast in a tiny weld is more fatiguing than a slower pace.

    One last item: I have to work at this scale by adding more magnification to my welding lens. I have to use 2.5 magnifiers for my hood (reading glass lens); but to do this level of work I had to put on reading glasses of 2X, inside the hood(!) so I ended up with a 4.5 magnifier! I know, that's an indication I should have asked a younger person to do the work? but.... that wasn't really in the work scope so I had to do the welds and "take what I got".

    Hope these ideas help your future exploration of thin SS TIG welds?

    Cheers,
    Kevin Morin
    Kenai, AK

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    Re: Tig Welding 20 Gauge Stainless Steel

    You don't mention what size of filler rod but it is not uncommon to use Mig wire or even special small diameter wires. Also I think a 1/16" tungsten would have been a better choice.

    https://www.amazon.com/Weldtool-Micr.../dp/B079P4MVTX

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    Re: Tig Welding 20 Gauge Stainless Steel

    Try about 50 pulses a second at about 20 percent background. 040 or 1/16th tungsten sharpened to a long needle taper.
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    Re: Tig Welding 20 Gauge Stainless Steel

    Just saw Ltbadd beat me to the punch...
    Sanrex Sanstick 140s(hotstart&dig set perfectly)
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    Re: Tig Welding 20 Gauge Stainless Steel

    +1 on pulse. I use about 33% at peak amps, 33% background and 20 pulse/sec but I don't think there's any magic in those settings, I think anything close will help.

    Fit up is also essential. Shoot for edges actually touching if you can. I find it's best to use fusion if possible and only use filler if you blow a hole or have a gap that you can't get good fit. I use 30 mil 308 MIG wire for 20g SS.

    On the piece you made I'd probably tack the ends and two more places in between before making weld.

    I also agree on back purge. I'll tack my assembly together without purge and then set up the purge for the welds.

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    Re: Tig Welding 20 Gauge Stainless Steel

    Thanks for all the help everyone. Lots to think about. 1/16 filler is what I tried. Will def try 1/16" tungsten, pulsing and chill bars/blocks. Would need a dual flowmeter for back purging. Will look into that.
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    Re: Tig Welding 20 Gauge Stainless Steel

    Quote Originally Posted by sand_man_red View Post
    +1 on pulse. I use about 33% at peak amps, 33% background and 20 pulse/sec but I don't think there's any magic in those settings, I think anything close will help.

    Fit up is also essential. Shoot for edges actually touching if you can. I find it's best to use fusion if possible and only use filler if you blow a hole or have a gap that you can't get good fit. I use 30 mil 308 MIG wire for 20g SS.

    On the piece you made I'd probably tack the ends and two more places in between before making weld.

    I also agree on back purge. I'll tack my assembly together without purge and then set up the purge for the welds.
    That is pretty close to Jody's "Rule of 33".
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Tig Welding 20 Gauge Stainless Steel

    Quote Originally Posted by shovelon View Post
    That is pretty close to Jody's "Rule of 33".
    And as Jody says that's just a starting point...

    nothing magic about those settings (what I say )
    Richard
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    Re: Tig Welding 20 Gauge Stainless Steel

    Quote Originally Posted by LtBadd View Post
    And as Jody says that's just a starting point...

    nothing magic about those settings (what I say )
    True. Miller's default pulse settings are 100pps,40% peak time, 25% background amps. This is a pretty soft setting, almost cold. For the most part I keep DC pulse on to keep my autodark triggered, with 200pps, 95% peak time, 85% background amps. Almost useless but throws out a soft hum to remind me pulse is on.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Tig Welding 20 Gauge Stainless Steel

    Aluminum chill/purge backer, and a gas lens(5 or 6) would probably make the biggest difference. Finding a backer for curved surfaces is usually my greater challenge. 1/16" vs. 3/32" tungsten hasn't seemed to make as big a difference for me on either transformer or inverter machines(you may find otherwise). Being able to see the weld properly makes a big difference, either obstruction or focus can be issues(mine is a x 1.5 diopter). With stainless you really have to start and move fast. Lots of tack welds first help too.

    good luck

    Is a #5 glass nozzle = pyrex gas lens ?
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    Re: Tig Welding 20 Gauge Stainless Steel

    Quote Originally Posted by albrightree View Post
    Is a #5 glass nozzle = pyrex gas lens ?
    Thanks for the insights. No, not a gas lens. Was using this: https://furickcup.com/product/ally5-cup-for-920/
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    Re: Tig Welding 20 Gauge Stainless Steel

    Quote Originally Posted by shovelon View Post
    True. Miller's default pulse settings are 100pps,40% peak time, 25% background amps. This is a pretty soft setting, almost cold. For the most part I keep DC pulse on to keep my autodark triggered, with 200pps, 95% peak time, 85% background amps. Almost useless but throws out a soft hum to remind me pulse is on.
    Haven't tried settings that high and close to each other, I have been in the neighborhood of 70% and 40%. I'll give your settings a try...
    Richard
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    Re: Tig Welding 20 Gauge Stainless Steel

    I tend to weld that thin stuff on 1 to 1.5 pps, 25% peak, 20% BG, and weld both sides. I call this a 60/60 weld. You get 60% penetration per side and it keeps warping way down. That is without a backing strip. If you use an alum plate, have to weld hotter.

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    Re: Tig Welding 20 Gauge Stainless Steel


    robert-r


    Just read the entire thread . . .

    You should be a 'happy camper' - all responses are focused - and loaded
    with sage advice . . .

    I have only done two - Mil/Spec weld projects [albeit narrow parameters].

    Compared: to the Fluent/Specs and directive/forward advice; my welding
    skill level
    - is little better - than a beginner in this league . . .

    If you don't understand the advice - research on your own time - and get
    back [to the WW] with semi-informed questions . . .

    My hand welding skill is mediocre - my technique/engineering is better . . .

    If: I were called to your project [perfect embodiment] - the 'chill bar' would
    be 'conically turned' in a CNC lathe [increasing radius] - then a mill cut,
    perpendicular to the tangent to provide a gas/back-purge galley.

    With: high upside/side welding skills - the back-side will look even better -

    hth -


    Opus

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