Swimming pool????

Discussion in 'Other metal working projects' started by Jason, Aug 1, 2018.

  1. Interesting link. We were welding 316 and 347 piping for petrochemical use. Cleaning consisted of power wire brushing with new stainless steel wire brushes. Cleaning was not done for appearance but for corrosion resistance, and as the article stated a clean surface will passivate itself in air. The article seems pointed at acid treatment and I wonder if it is primarily for food industry purposes. I'm no expert in anything but I would power wire brush and forget it. I'd probably wind up with dark HAZ.:eek:
     
    Jason likes this.
  2. Jason

    Jason Gold

    Hey Andy... What's your voodoo magic for keeping plate from warping? I had a very educational phone call today from Zila off of youtube. He's not a youtuber per say, but just shows some of the work he does. His concern is warping I will encounter welding plate. He said pulse mig will help, but the real solution could be double pulse and flux cored wire. Double pulse has been around (again) in europe for years and is kinda new here in the states. He also added, the stiffeners pre welded to the backs of the sheet would aid during the miles of butt welding. He suggested using angle stainless for braces and bought of lower grade 304 and the fab shop work skipped out on. :D Money saved there could be used for the purchase of the propulse's bigger brother. That's the PP300. It's approaching 5grand... Its US competitors are north of 8k. Good toys are never cheap.:oops: Double pulse puts way less heat into the piece thus helping to prevent warpage. ThePP200 does double pulse, but only on aluminum settings. Odd I agree... Maybe a software upgrade could fix this in the future?:(
     
  3. I think chrome is the hardest metal element known to man, it's entirely possible you were removing the iron and nickel from the surface and leaving a pure layer of chrome behind. That article is describing pickling to clean the surface including iron contamination, as well as passivation. I tend to mix the two together as I understand nitric acid does both, being a strong oxidizing acid that etches the iron.
     
  4. Jason

    Jason Gold

    I guess warpage didn't bother these guys. This is 1.5mm thick SS.

    zeller_schwimmbecken-edelstahl-bauweise-9.jpg

    Here is an interesting construction method. Probably done in panels and transported to the site.

    zeller_schwimmbecken-edelstahl-bauweise-2.jpg
     
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    Jason, I knew you were crazy, but now I think your "Just plain nuts"
    PS, its difficult to find a good picture of a penis shaped pool to post for you..... :p:D:rolleyes:
     
    Jason likes this.
  6. Jason

    Jason Gold

    That was the first thing I told Pete today.. TALK ME OUTTA THIS! Instead, he probably sold me a more expensive welder. :eek:
     
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    thats what friends for...roflmao....
     
    Jason likes this.
  8. Does the iron contamination come from separation of elements during welding?

    From what I read it appears good cleaning is passivation. I never understood passivation, and I'm batting 1,000.

    Jason: I have no idea how to minimize warping in stainless steel welding. Air quench like in carbon steel sheet metal welding I would never do somewhere that I really did not want cracks. On heavy wall stainless pipe (8" 3/4" wall) the pipe will neck down enough at the weld that you can get a good cap on the weld which is actually below the surface of the pipe away from the weld. I think your best bet is MIG with a backing plate and accept some distortion. Or slow TIG.

    If you really want to be talked out of it, buy some strips of SS and start practice welding.:eek::eek::eek:

    Then check with the guys in Europe and see how much they would charge for a prebuilt pool in a container shipped to your door.

    This is going to be an epic thread.
     
  9. Another thought about warpage. When you think about warping during welding I usually think about liquid metal shrinking upon solidification and pulling the solid pieces attached to it. So welding the opposite side counters that, but with the first weld in place it takes more weld to pull it back, like a plate welded on edge to another plate. And of course skip tacking helps produce a rigid structure so all the welding stresses pull on the structure but don't warp it. But with sheet metal one of the primary issues is the area near the weld warm up and the weld ties it together. Then when those warm areas cool you get a bow, bubble, or oil canning. That's why hitting sheet metal welding with an air jet immediately upon welding a spot minimizes warping: you are keeping the entire sheet relatively cool. A backing plate would surely help so long as you minimize heat input but still get a good weld. Maybe you can quench 316SS and still have a good weld. But any passivation is a total waste of time if you have micro-cracks in the welding which let chlorides into the steel. A propagating crack is worse than discoloration.

    A gunite pool floating in a select fill bed looks better to me.
     
  10. Ha ha ha!! I just realized there is no water in that pool.:D

    Probably not bad results after you've sunk the money and that is your result.:eek:

    "Steps off soap box and leaves."
     
  11. Edit: 316 is about 65% iron, not 70% stated below:
    316 is about 70% iron so it's right there in the material, it doesn't have to be a contaminant. Passivation on the other hand is a protective layer of clear oxide, anodizing aluminium, titanium is also passivation, every bit as much as the much thinner layer of chrome and nickel oxide in stainless, even brass can be passivated. The problem starts with the 70% iron content as iron oxide is just scale or rust and gives no protection to the metal. The classic cause of serious corrosion on stainless is a low oxygen marine environment like an anchor in the mud at the bottom of a harbor for a long time: it looks like termites have attacked the anchor. There's not enough oxygen for passivation to re-form on the surface and the salt corrodes the iron.


    The photo below shows 316 when the passivation layer is broken in the presence of chlorides.

    316 tube pitting.jpg

    These are 35 year old passivated brass clamp castings, the G clamp on the bottom left was made as part of the same batch but was not passivated in a nitric acid bath like all of the other castings pictured. All of the G clamps have been in regular pattern shop use so they are no longer pristine.
    passivated 1.jpg

    passivated 2.jpg
     
    Last edited: Aug 21, 2018
  12. Jason

    Jason Gold

    I'm on the hunt for some 316 today to screw with. I want to see what this stuff is really like to deal with. Up to now, I've already learned way more about stainless than I ever wanted to. Not that that's a bad thing. If ya dont learn something new each day, it's a waste.

    Hey Andy, If I welded that thin 1.5mm and it came out like that.... I'd be happy! :p Now paying someone big money for that would make me cranky:mad:

    Time to find some tank welders. They should be the pros at this stuff. I'm a knuckle dragger.:oops:
     
    Last edited: Aug 21, 2018
  13. Jason

    Jason Gold

    SO I spent a couple of days in Houston.... First thing I learned besides their traffic and roads are a nightmare is 316L is extremely hard to come by. I've found a supplier for now. Odd thing, they sell this stuff by the pound! ?:rolleyes: Current price is $2.70 a lb. OR for 1/8" 11ga, it is around $13.60 per sq foot. But god forbid you try to buy a DROP that's about a foot square. That'll set you back 120bucks. I showed that company their invoice to me for 13k and explained I needed that piece for tests. No love. I told him to keep the piece AND their invoice! No worries, they were 15bucks a ft. I'm learning it appears ALL this stuff comes from china. Is the USA outta the stainless market? Sad.:(

    A new potential supplier I found only scrounged up a 10ft piece of 11ga strap that was 1" wide. Yeah, that was 50bucks. SMH and paid the man. Don't wanna piss this one off, he's 13bucks a foot. 4th welding supply store later (not airgas) I found some 316L filler wire, 8bucks a lb and whacked up a few pieces of strap. I wanted to sit down with the tig torch and see what all the fuss was about. 130amps, 20cfm, I laid wire over a 1/16" gap and just drove over it as quick as I could. Flipped it over, no filler wire and just drove the bead. Hmm. That wasn't too interesting. Next I took two coupons, laid them tight up against each other, no filler wire and just drove a puddle. Flipped and repeated.
    Hmm. I must be missing something here. No fancy dimes here, you got the wrong guy. I need FAST with minimal effort and skill. The stuff welds nicer than mild steel and bronze. Dare I even say this, Why do I envision a tig torch holder on a track driving over 20ft welds??? "Hey honey, mash that pedal and close your eyes while I push this thing down the driveway" ?????

    I need to now cut these in half, polish and etch and see the quality of the weld. Same for testing inside/outside corner joints.

    20180822_213023.jpg
     
  14. Bite the bullet and test. Great!!

    Looks good. Looks hot. Welds look too big to me. How much warpage did you get? That 11 gauge is heavy stuff. Automatic TIG is very practical. Better than a steady hand.
     
  15. Jason

    Jason Gold

    Too damn hot! Told ya I'm learning! ;) Just read 5 minutes ago, ya go 1 amp per thou then subtract 10%. Sound right to you? Back to the table I go. Warpage? How about none on these, but they are pretty small to tell honestly. I like 1/8". Zilla is suggesting 3/16" and he's probably right. I'm scared to price that out. In addition, sheets that are 11ga 5ftX12ft are 300lbs. I will need 3 of these welded on the long side to form the main bottom. I really gotta work on some drawings this weekend.
     
  16. Jason

    Jason Gold

    I'm too slow. To get this, I'm having to haul some major ass. Is this a fast process?
    15349978711275069796953472484141.jpg
     
  17. I would have set the machine at 60 amps then never get the foot pedal to the floor. You are using a foot pedal to control? You want minimum heat input and it is a slow process the way I do it. I'm no expert welder but I've burned a lot of rod.

    Nice smooth welds. You really don't need full penetration but I'm guessing you won't be back welding the bottom. And you're probably going to have to tack every three feet before you start to keep the sheets together.

    buy some 16 gauge and try it. You don't need 316L for playing around. Regular old 316 will weld the same.

    You might succeed with tight butting the sheets and building a track for your TIG torch then let it haul ass down the seam with high heat input but moving quickly which will keep the heat down. You'll need to grind starts and stops and probably have to do something like a running start (turning on the arc after the torch is moving) but with the job you want this is not a normal TIG setup. I'm starting to get interested in seeing you do this. And a carefully aligned track, variable speed motor operated traveler, and accurately set tungsten you can build yourself a bulletproof seam welder. You may get weights to hold the track down (magnets just don't work) or you could drill and tap holes then plug weld them or screw nice round head screws in with nitrile gaskets to seal the hole. This might be necessary on your vertical runs. Plan on getting a plasma and using it on your track to trim your two sacrificial sheets you will want to use to get the process dialed in before going out on the town.
     
  18. Jason

    Jason Gold

    Jody teaches "keep stainless; stainless" So I am guessing it's possible to burn this stuff? One guy told me when you get it too hot, it burns the chromium and something else in it right outta there and you loose the rust protection if ya don't use filler rod. :confused: I'm guessing 75% of this welding job will be butt welding.... A track system would be the catzazz to make short work of this. I already own the tig machine and yes it has a foot pedal. I haven't figured out how these guys make shiny SS welds yet. It almost looks to me like they are brazing with stainless and not achieving full penetration but what do I know. These pieces must have full penetration and with 11ga, I don't see that being that hard to accomplish. I cleaned up my overheated work from last night, both with and without filler, ground them smooth and they are enjoying some serious salty water now.

    15350484460506008906040302018258.jpg

    I better cut up more coupons and spend some time in the seat learning how to do this.
     
  19. DavidF

    DavidF Administrator Staff Member Banner Member

    Are you running a diffuser on your torch?
     
  20. Jason

    Jason Gold

    Gas lens? Absolutely
     

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