Stainless Question

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does anyone know what element makes SS turn teh colors it does when it is properly welded? just curious. i love the blues and oranges that come from a properly welded joint and was curious if i could get those colors with another metal (besides Titanium). also, is there one alloy that has a higher percent of this color changing material? it may be hard to understand what i am asking...if it is the nickle in the SS that makes it change colors, can i get a high-nickle alloy and expect it to do the same thing? or is it due to all the components of SS combined that make it change colors?just curious. i'm thinking about what to make for some Christmas gifts. i know there are some enginers/scientists that can answer this pretty quickThanks!Later,Andy
Reply:18-8 CR-Ni (308) CR will change colors and is probablywhat you are looking for.  JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:You can get those same colors from regular mild steel- especially thin sheet- if you polish it up nice and shiny, then "draw" on it with a very small tip on an oxy-acetyelene torch. But regular steel will oxidize (rust) quickly, and the colors lose their brightness. I used to make some chairs where I would draw on em with a torch, then clearcoat em right away. They lost some of their brightness, but not much.High Nickel alloys are incredibly expensive. The more nickel in a stainless steel, the more it costs- and regular 304 stainless, the most common alloy, depending on shape and where you buy it, can run anywhere from $3.50 to $8.00 a pound these days. Various Nickel alloys can easily break ten bucks a pound, some pushing up towards 20. If you overheat either the stainless or mild steel, you get dark blue/gray pretty quick- the trick is a very small tip, hot and quick.
Reply:Those colors are just a form of oxidation of the steel alloy.As Ries said, you can get those same colors on mild steel if you bright polish the steel first and then carefully heat it.  The problem with plain steel, as Ries pointed out, is that it will oxidize (rust) all by itself and those "pretty colors" will get lost in the rust pretty soon.And those 'pretty' blues and oranges on a welded stainless joint?  They indicate that the weld oxidized somewhat as the hot steel cooled, which means that the shielding gas or flux/slag wasn't there as the weld cooled.  Sometimes that oxidation makes a difference in the properties of the weld, and sometimes it is just cosmetic.  A 'proper' weld won't be oxidized, because the  flux/slag or shielding gas did its job and protected the hot metal from the atmosphere.  Titanium is -very- sensitive to degredation from hot oxidation, so a 'proper' titanium weld needs to be well shielded from oxidation.  That's a reason that many titanium welds have to be done in an inert 'glove-box' chamber.Want to experiment?  Take a plain piece of steel and heat it.  Watch the oxide colors form as the metal gets hotter.  You can do this by accident with a grinder on a piece of steel.  If it happens to be a blade or other hardened piece of steel that you were grinding, you probably just screwed-up the hardness and temper of the steel!  Another experiment is take a piece of steel and weld on it.  Flip it over and look at the oxide colors on the back side from the heat of the weld.
Reply:I'm with MoonRise on this one.
Reply:MoonRise is correct.AWS has a photo showing showing a series of welds made with Argon doped with various levels of Oxygen, and 50 parts per million (ppm) O2 begins to produce straw or gold, while around 500 ppm produces blue, and around 1000 ppm brings in purple.
Reply:interesting info here guys. thanks for all the input. so to sum it all up, the "pretty colors"  really shoudln't be there if the weld is completely shielded right? if that is the case, the weld should actually be silver in color (similar/the same as the base metal?thanks guys.I appreciate it.later,Andy
Reply:Actually when its welded "correctly" there should be no color. It is colorless when welded in an inert atmosphere.
Reply:Try heating sheet copper (cut into leaf pattern or similar)(for that gift phase) then wax or shellac the surface to preserve colors.Some heated metals can be as neat as a sunset.