Colour Formed Approx Temperature C
pale yellow 290
straw yellow 340
dark yellow 370
brown 390
purple brown 420
dark purple 450
blue 540
dark blue 600
Hope that's what you are looking for.

 

Its not really the temp, its the oxygen content of the atmosphere touching the metal while its above about 4-600

 

Its both, with the temperature low the oxygen content doesn't matter.
If you are purging then you look at color of the purged side to check for oxygen content of the purge(color).
When looking at the torch side you check color to see if the steel was below a temperature before losing shielding. (I think the reason for the difference is that the purge side and the torch side both have different colors that are acceptable depending on application.) Hope that makes sense

 

Should be in your text book, I think.

I go by "anything but gray is ok"

I always thought purple was on the hotter side than blue. I usually get blue at the beginning of the weld, then light yellow, then gold, and if I stick around too long the gold turns into a purpleish gold, then gray.

 

Hello Tyler, see my next post. The file sizes screwed up my attempts to attach them here.

 

Hello Tyler, are you referring to purge levels possibly? Colors in stainless steel welding can certainly come from temperatures, yet, results from welding are relative to shielding and time at temperature as well. If you have a good shielding system you will end up with "silver" welds, as the lack of shielding comes into play the colors will show up as a result of exposure to atmospheric oxygen and the longer that the material is at a reactive temperature and the more oxygen that it is allowed to react to will promote the display of different colors. I'll try to include a chart of how some of this comes into play. Best regards, Allan .

 

thank you guys so much i just started stainless tonight at school so i dont really know what color of weld is ok this will help a lot .
i know brown/gray wont fly at school so looking at the chart i will have to stop welding when my weld turns purple ?

 

i know brown/gray wont fly at school so looking at the chart i will have to stop welding when my weld turns purple ?

I think you may be misunderstanding Allan's post. The weld colors don't come directly from heat. They come from the reaction of the material at temperature in the presence of oxygen. You could weld as long as you wanted , if you protected the weld from O2 until it's below it's reactive temp.

If you are overheating the material, what happens is that it's still above that reactive temp when your shielding gas trails off as you move on with the weld. This exposes the still "hot" stainless to O2 causing the colors you see. How hot the material is, thus how long it stays reactive, determines the color based on the amount of O2 that reaches it before it cools down. A hotter weld stays reactive longer and so can be exposed to more O2 while it's still reactive. That's what the bottom of Allan's chart is showing.

It's not that you need to stop welding when the weld turns purple, it's that you need to either extend the time the weld remains within the gas shield so it cools before it gets exposed to oxygen, or you need to reduce your heat input, so the weld can cool before it leaves the size of the gas envelope you are already using.

The "trick" is to only put in enough energy to make your weld and not heat up the surrounding area any more than you need to. All that extra heat helps keep the bead reactive longer since the material can't help wick away the heat from the bead before your shielding gas is past the weld. It seams counter intuitive, but some times the answer is more amps, not less. By using more amps, you can melt the weld area faster and then the cooler surrounding material can wick away the excess heat. If you go slow with lower amps, you can actually add more heat because the material is constantly pulling heat from the weld into the surrounding material. Then that material can't take absorb that excess heat from the weld. There's a balance between travel speed, amps and arc length that needs to be found to get the results you are looking for, given a fixed gas shield.

 

Just buff it off, then it'll be silver.

 

Hello again Tyler, Doug gave you a very thorough explanation as to the reason for colors and their various levels. Consider that the GTAW process is unique to almost all of the other welding processes. It is one of the few that allows for such a wide combination of amps, volts, levels of addition of filler, and speed/progression. You "can" run very slowly with a lot of heat and varying amounts of filler addition, but if you weld in this manner you will likely see excessive indications of oxidation and in some cases a phenomenon referred to affectionately as "sugaring"(this usually occurs on the backside of your welds and is caused by full material thickness penetration, leading to unprotected molten weld metal). Simply stepping up your travel speed can drastically alter the appearances and conditions that apply to your resulting finished weld. Using backing/chill bars can affect the finished weld as the dissipation of heat will reduce oxidation conditions. Gas lenses, larger cup sizes, correct shielding gas flow rates will all have affects on finished weld colors along with travel speeds and heat input levels(amps). You've got plenty ahead of you to figure out the many nuances associated with this process and it's applications. Good luck, have fun, and regards, Allan

 

ok now it makes sense thanks for the imput guys just for the record im running 60 to 65 amps on thin wall pipe with a number 10 alumiacup with a gas lens running 20 cfm of gas .
im getting really good welds i just got to tighten up my walk ill post up pictures later tonight

 

Look forward to seeing those Tyler. Weld away! Regards, Allan