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Dull stainless steel weld with filler metal

Motorsport TIG Welding Fundamentals

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Hello,

I use a golden tungsten in 1.6 mm with 304L stainless steel filler metal 1.6mm.

When I melt the 2 parts of the stainless steel tube, the color is very beautiful, bluish, when I use filler metal the color is dull. I tried filler metal in 316L nothing changes.

Do you know why and will you have a solution?

Thanking you in advance ✌️

Can't advise, but for those that can, are you using the same gas mix and what is it, also are you using the same gas flow?

If you're using a filler that would suggest you've a gap, have you purged the pipe with your gas of choice, as it may be picking up some contamination through the gap?

I'm definitely a neophyte but grey welds are almost always from too much heat. Autogenous welding - to me - is relatively easy to manage heat so long as fit up is good. When I start adding filler I notice my heat management goes to the toilet though slowly but surely getting more control.

Are you welding the pieces together with the aim of achieving a type of color or strength.

I personally have never managed to master the art of pretty colored welds.

I know that it comes down to oxidation and that is achieved by travel speed, amps/heat and gas coverage. With adding the filler wire it may be down to the weld being colder but there is really a multitude of different variables that can have an impact. The only real answer is torch time and playing around with the settings on your welder

Your other option is not to worry about the color and use the nasty pickling paste or if your rich, a tig brush to clean your welds for an oxide free finish. Its funny that the automotive industry is the only industry that strives for oxidation in the weld appearance, all others require the removal of it.

Numerous variables can cause excessive oxidation of stainless steel. It may be difficult to answer your question without seeing the welds and your torch setup. However, the most common mistakes are too long of an arc, too much torch angle, and failure to keep the filler rod within the shielding gas envelope during the welding process and while post-flowing.

Technically, any coloration on stainless steel after welding would be considered oxidation. With an entirely silver weld being ideal, the following colors in the chart are formed during exposure to the atmosphere. This should give you an approximation of the temperatures you are seeing in relation to the color.

Color 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