Welding Tips and Tricks

Stainless, Titanium and CrMo... I see these beautiful welds and know the Stainless should look like chrome, the Ti, goldish to silver. What is going on with the various colors? Poor gas coverage, overheating? Trying to learn more. Thanks in advance

Color on stainless and Ti is the result of the reactive properties of the base metal. You can search online for a chart that gives the temperature range for the color result. Ideally, "straw" is the preferred for Ti and Stainless as it is indicative of good gas coverage and proper travel/heat mix.

Both Ti and Stainless are tricky to weld. You can have the right amps, but travel so slowly that the results is overheating, grey welds. That is not good.

I'm no scientist, but I believe the color is directly related to the thickness of the oxide layer that is formed (in our case as welders, due to a combination of heat and shielding gas as CJ mentioned). The different thicknesses of that oxide layer will refract the light differently depending on the thickness of the layer, and that is why we see the differing colors in a full spectrum. The colors in the spectrum (thickness of the oxide layer) are directly related to the amount of heat when oxygen is present. So in theory, as long as the part is completely shielded from oxygen while it is in that specific heat range, it will always remain "silver".

The colors of your welds are a great learning tool for controlling your heat input, especially when welding stainless. However, in most practical applications, the colors of your welds have very very very little to do with whether or not the weld is a good weld. Also, in most practical applications, that oxide layer (essentially, the colors) will all be removed through passivization prior to putting the part into service.

I've heard the same thing that spartan mentioned about the colors being caused by varying thicknesses of oxide layers, whether the oxides are Chromium, titanium, or otherwise. I will say also that even if you have perfect shielding gas coverage, impurities will also prevent a "color-free", or perfectly silver weld. Those can come from many different sources. Some that are common are any kind of hydrocarbons, oils, greases, residue, moisture, dust, grit, or anything else on the surface of the base metal and/or the filler metal. The extent of concern about that varies by application and by the metals being welded. Also, shielding gas that isn't pure enough or is subjected to contaminants anywhere along the way can and will discolor the weld area. So if you need a perfectly color-free weld as is often the case with titanium, you want to take great care in cleaning the base metal and filler metal, using clean gloves and a solvent that doesn't leave residue behind. You can test this by applying a small amount to clean glass and seeing if it leaves residue once it vaporizes. Hope this helps.