Stainless colors

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Hi people, great forum this is, packed with info.  I have a question about SS. I am going to weld up some " artifacts" with my TIG. I want to know which SS alloy and filler rod is the best for those purty rainbow colors I have seen on stainless. THanks.
Reply:Hey Burnt,  Those "purty" colors actually come from the proper amount of shielding gas and heat when welding.They can be achieved when welding mild/alloy steels as well. No special rod needed.- Paulhttp://all-a-cart.comWelding Cart Kits and accessories
Reply:As ZTFab says, the colors are related to shielding, more precisely lack of shielding.  A perfectly shielded weld will have no color, only shiny metal.  Oxygen, nitrogen, and contaminants like oil or whatever are what cause the discoloration by forming oxides, nitrides, etc.  In general, clean stainless steel will begin showing straw/gold color at about 50 parts per million (ppm) of oxygen in argon.  As oxygen content is raised, the color progresses into blue and then dark purple (more or less).Don't know the actual temperature required to cause discoloration, but it may be only around 500 F?
Reply:So, for example, you are saying the weld in this first pic is better than the weld in the second pic?  The discoloring is contamination?(these are just examples I found online) Attached Images
Reply:SS discoloration (gold/blue/some purple) only really matters for critical applications of cleanliness like semiconductor, pharmacutical, or BREWERY piping, or for corrosion resistance like in acid/caustic/marine, whatever stuff.  So, for lots of applications, just wire brush of the discoloration, it has no effect on gross strength.Now if you sugar the weld, that is severely oxidize it into a crusty mess, that will affect strength.The strength properties of Titanium are extremely sensitive to oxidation as indicated by discoloration, so it not just a matter of asthetics, it is critical with Ti welds.
Reply:Found some pics of weld color versus Oxygen content in Argon.http://www.intercononline.com/welding/ypurge.htm
Reply:I printed that one, thanks PulserDavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Is it possible that in the pictures that TSOR found, that the most discolorized one was heat treated after welding?Don't talk about it, Just do it!
Reply:Could be Vicoor.Those appear to be the bottom bracket of a bike frame (where the crankset goes).It's most likely Titanium and the first one might have been welded in an inert atmosphere and the other not?- Paulhttp://all-a-cart.comWelding Cart Kits and accessories
Reply:Originally Posted by VicoorIs it possible that in the pictures that TSOR found, that the most discolorized one was heat treated after welding?