stainless steel welding, help please

hi,
I have a question about welding stainless steel plates 1/16" in thickness. i will need to create a square bowl in a specific shape , which will
be used in a "food grade" type application.
my question is , I got a MIG , and I can get solid SS mig wire for it. I only have C25 gas, which I know is not the proper shielding gas for SS can i use C25 and what wil be the outcome.
do I have any other options.
thanks
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The only downside to C25 is that you will get a very thick layer of oxides around the weld. As long as you grind the surface clean you will be fine. You will still have to passivate the surface after grinding.
Keep your wire stick-out extremely short with SS.
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thanks ernie,
please tell me what is involved in "passivate"-ing
On Sun, 25 Jan 2004 22:29:16 GMT, Ernie Leimkuhler

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acrobat-ants wrote:

Go to welding shop, ask for s.s. "pickling" solution. It can be ordered in a couple of sizes, usually the smallest size will last a long time, usually a couple of liters. It is in the form of a gel.
It's another combination of nasties, including hydrofluoric, nitric, and sulfuric acids. Wear lots of protection, including respirator, thick rubber gloves, and use in a well ventilated area. Apply between 15-45 minutes to treat the metal after welding. Rinse with lots of water. Dispose according to local regulations and laws.
What it does: it leeches out iron at the surface of the s.s., leaving the chromium and nickel oxides at the surface, thereby increasing corrosion resistance. It also removes the welding scorching. Most medical instruments, and food applications need to be passivated to prevent contamination. If you don't passivate, a light coating of rust will likely form in the vicinity of the weld after immersion. The pickling solution will leave a frosted finish to the stainless.
Alternatively, if you can find a metal treatment shop, including such things as electropolishing, and passivating. Most shops use nitric acid baths, and don't do as good a job as the pickling solution. Caveat Emptor.
Guy
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thanks for the informtion guys.
wrote:

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ok, here is an other question
welding thin stainless steel using A/O torch, what is needed? special filing rod, special flux? what are the precautions.
thank you
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You need a carburizing flame where the carbon feather is at least 3 times as long as the inner cone. Weld as quickly as possible. This will impart some carbon into the SS if you weld slow.
No flux is needed. Use standard 308L TIG filler rod.
With a carbirizing flame the SS becomes very fluid, and flows really well.
It is more like high temp brazing without a flux.
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thanks Ernie,
do I still need to passivate the stainless after the welding is done using A/O as mentioned below , if it will be used for food application?
On Fri, 30 Jan 2004 02:42:12 GMT, Ernie Leimkuhler

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Yes. You still have to passivate it somehow.
The most likely side affect from OA welding stainless is too much carbon in the weld which can cause chromium carbides to form, which can lead to fractures.
I have never had this trouble, but have had many metallurgist types warn me of such.

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What about using flux and a less carburizing flame? I've used it, but not enough to say if it has significant advantages.

--
C++: The power, elegance and simplicity of a hand grenade.

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