I've been trying to get a rainbow colored weld like the picture below and I just can't do it.I've went through pounds of 308L and yards of stainless tubing.I've changed my amps and shielding gas flow rate but I can't seem to do it.I clean the hell out of the stainless and still nothing.Please help this lost soul... Thanks
I may be wrong but if you are doing it right you dont get rainbows. going too slow too high amps cause that effect. it usually results in a brittle weld. but i am open too be corrected. lets learn something here.
I 2nd what 972toolmaker says. It allows too much heat in that area, and the result is brittle. ?? Anyone sayin different, I would like to know the facts
A perfect weld on stainless will have no discoloration. The colors are usually a result of oxygen contamination from a lack of shielding gas coverage. Stainless does'nt like too much heat, so try rocking your pedal as you weld (this will give a bit of cooling to your weld) and also play with the flow rate. Try not to get too much heat in your part, to much heat will turn your stainless a gray color. You can also get your flow rate too high and this can cause some turbulance around the weld area and allow oxygen contamination. Contamination can also come from the surface of the material, so clean it extremely well before you weld. If you do wind up with rainbow colors when you finish welding "Clean It Off" as this can allow rust to form due to the contamination in the weld. Hope this helps. P
Hope this helps.: Stainless steel is a fascinating metal to weld. I have spent many years welding different grades of stainless steel. Needless to say I have picked up a few tricks along the way to make the process a little bit easier and of course to produce better welds. Welding stainless can be difficult if you don't know what you are doing. It reacts to excessive heat by warping and distorting once it cools. Everything shows up in stainless. What I mean by that is if you weld with too much heat you can see it by the heat marks left in the metal along with any distortion. It also scratches very easily so you must take care when welding on a metal table. One of the best things to do when welding stainless is to use a heat sink such as brass or aluminum. I usually clamp a piece of 3/8 brass behind the seam of the weld. This absorbs the heat and also prevents any burn through. The trick with stainless is to put as little heat into it as possible, especially with thin material. It's worth the extra time to make sure you have the heat sinks in place before beginning your weld. This allows you to actually weld the entire seam without interruption
The welds in the picture look fine to me. I've seen that on 303 stainless and it will wire wheel out. The welds look fine and surely not overheated. That is an "up" weld joint and they tend to run hotter than a "down" weld and are inherently stronger. I would say, do a couple of t-joint test welds, clamp it in a vise and give it the BFH (big f***ing hammer) test. Bob
i weld with a guy at work (sean)who was taught by literally a master welder and master engineer. sean attended two welding schools at which one he was given all of his tests of the courses in the first few monthes to finish because he was that damn good. with still 2 years to go of school what was he to do?? the school payed him to teach (which payed off his schooling) hes been welding since he was 16 (37 now) hes welded like everything in the world many a times. :THE POINT: he was teaching me tig on stainless and told me that you want the rainbow. that tells you your heat was right. if your too hot it will just be gray. too cold obviously it will be balled up on top. im pretty sure (cant remember good enough) he said when the metal cools its releasing carbon or something of that nature and if your too hot the heat of the weld traps it in there..keeping it gray in color.. your weld should be cooling off (gray first) slowly turning rainbow colored. im not sure i was any help.
The color of the weld does not matter as much as long as you are getting proper penetration without excessive penetration. Excessive penetration will allow for atmospheric contamination on the back side of the weldment do to the lack of a shielding gas. You also want to make a convex weld verses a concave weld for a nice strong joint. I noticed for me, to get a nice gold color on stainless. I run a champagne cup with a preflow of 1 second with a postflow of 10 and run the flow meter at 20-25 CFM.
Good interesting thread. It doesn't sound like we have a definite agreed upon answer yet. I am with grarlytyler and 408 AA/D. My ears are open. Wil www.sakowskimotors.com
I think we are all on the same page, The discoloration has nothing to do with the quality of weld. Looks like a result of a thin material with welds that are too wide. Looks great and will hold very well. Typically the idea of tig welding is to apply just enough heat for proper penetration and flow, allowing impurities to wash aside without applying too much heat to prevent warpage and effecting the ductility. Tig welded for 20 years. Certified pressure vessel. I wish my eyes were still good enough to apply a weld like that.
Know anyone that works around heat treat furnaces? Ask em about heat rainbows, and they'll tell you it varies day to day depending on weather and shop environment and level of cleanliness. What's happening is your arc is vaporizing components of the atmosphere, which condense on the cooler steel surrounding the puddle. You can vary the color of the rainbow by varying what's in the air. Until you fully control the weld environment, it's not a good measure of heat because you're judging 2 variables at once. Air and heat. So which one really did/didn't cause the rainbow??? The guy at home without metallographic equipment probably isn't going to figure that one out. Happy welding.
There's a guy on here who knows everything about welding. http://www.jalopyjournal.com/forum/showthread.php?t=93721&page=3
i welded stainless for a living, actually the discoloration is contamination. and to be properly welded it should all be light gold in color with no other colors. you will want at least 5 seconds of post flow on your machine. also you will need rear purging too. if you see black crustys on the back side that is contaminated and will crack. hope that helps. i guess i should just give you the run down. put the rear purging block(that you make) on the back side of the weld area. then strike the arch and go for the bead *dip dip dip dip dip* let off the arch slowly and in a circle. after the arch has stopped and the gas is still blowing, hold it there for about 5 seconds, then pull away. should be gold, if you see blue start behind were you are welding you are either moving to fast, going to far, or need a bigger cup on your tip.
Yes you are running to high amps. Back it off to where it won't form a puddle and adjust up until it does and keep the gas covering the weld and oscillate the puddle as you move away. Use a larger cup that allows better gas coverage. Use pure argon. Don't let the tungston protrude any farther out then it has to.The closer you hold the tungston to the work the better it will weld, and will require a lower amperage.
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