stainless steel tig ????

admin

ok guys im going to tulsa welding school and im in phas 8 now and we are doing stainless steel tig on a 2'' schedele 40 pipe and im having some issues with instructors i just cant get the same anwser  from them i run my root at about 110 and hot pass and fill at 125 and the cap at 140 it always turs out silver and blue and not gold so the instructor i have now is giving me lower grades than everybody else because its not gold but other instructors says silver is better than gold i need some help does anybody kno the right color thanks
Reply:So long as your backpurge is good, your toe is wetted in properly, and you have good puddle shape and penetration, you should not have any problems. My better welds are usually gold/ silver colored, my bad ones are blue, and my really bad ones are black......with chunks of tungsten melted into them!!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:What are you planning to do after you are finished with school?UA Local 598
Reply:Your welds are silver and blue?  Thats odd, because those are on the opposite sides of the color spectrum.  I would expect to see some inbetween colors as well.  Technically silver is ideal, because it means that the weld material was relativley cool when the shield gas was removed.  Blue is at the high end, and though it wont be a problem on stainless if you see blue on TI welds, they fail.However  I agree with the above, color really shouldn't matter on stainless as long as the root has a good back purge.  Ask them why one is better than the other, im curious to hear their answer.Have we all gone mad?
Reply:i would get both teachers together and get them to sort it out between them
Reply:Ah, for real?from my experience at the school, the color spectrum for oxidation is silver-blue-gold-purple-grey (purple and grey being bad).Greg, my instructor for the phase, would usually accept anything from silver to gold with some streaks of purple in it (of course, the closer to cooler the better).If you are positive that your welds are coming out blue and you want them to turn gold (if you can't convince your instructor that it shouldn't matter), just lower your travel speed/crank amperage up/whatever and let more heat get into the weld. of course, keep in mind all the factors that come with extra heat (larger puddle, undercut, etc.) and compensate for them but if he wants gold more heat'll do it.Keeping it down in the hood...literally!
Reply:The color on and around a stainless steel TIG weld results from the hot metal reacting with the oxygen and nitrogen in the air.  If the weld is shielded with inert gas while it is cooled below some threshold it will be perfectly shiny silver with no discoloration, but this is generally only possible in a chamber or automated tube weld head where oxygen is less than 50 parts per million (ppm) or 0.005%.The amount of oxygen, the temperature of the metal, and the time it is exposed, all affect the degree of discoloration.  As condition worsen the color changes from silver (no color) to gold, blue, purple, black, then sugared.  Other than providing good shielding with a large nozzle and gas lens, discoloration is function of current, travel speed, and metal thickness, which all affect how fast the weld and base metal cools.  A small root pass on thick metal discolors less than it would on thinner metal.
Reply:Originally Posted by WHughesWhat are you planning to do after you are finished with school?
Reply:i got them together and they discused it the instructor i have now hasnt been tiging stainless for long so he really didint kno so joey told him that gold was the proper color but the silver was just a little bit better so they got it worked out
Reply:Thats weak. Are you paying for that kind of instruction?UA Local 598
Reply:That's also a lot of heat for 2" sch. 40 stainless...
Reply:Yeah that does seem kind of hot. Do you weld at light speed? Got some pics?PS. Your instructors sound like they dont know what the hell they are talking about.
Reply:Unreal....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by Drake AldanAh, for real?from my experience at the school, the color spectrum for oxidation is silver-blue-gold-purple-grey (purple and grey being bad).If you are positive that your welds are coming out blue and you want them to turn gold (if you can't convince your instructor that it shouldn't matter), just lower your travel speed/crank amperage up/whatever and let more heat get into the weld. of course, keep in mind all the factors that come with extra heat (larger puddle, undercut, etc.) and compensate for them but if he wants gold more heat'll do it.
Reply:the attached foto is ms not ss,..if the color  spectrum is different for ms than ss i apologize..but  what is of interest is as this weld goes from right to left, look at the heat  mark..where it goes to blue the heat  mark is shorter. then as it goes  back to gold and silver the heat  is building up higher..?? Attached Images
Reply:The color difference has more to do with travel speed.  You hesitate at the start of the weld as you form the molten pool prior to adding filler, so shielding is increased in that area.  Same at the end of the weld where you stop to add your last few dabs of filler and then wait for post flow.  Heat tint on the base material will almost always protrude out more near edges.  In the middle, heat can dissipate 360 degrees.  Towards the edges, if the heat can't dissipate laterally as pictured above, it's going to travel in the other direction.  Notice how the gradual accumulation of heat is linear on the top component from right to left, since the area for the heat to dissipate remains the same (no side edges).