Titanium Weld Colors can teach you something. Even if you don’t weld titanium, there is a cool trick where titanium weld colors help to test the quality of your torch gas. Stay with me here and learn the trick.
Discoloration of Titanium from the heat of welding is caused by oxidation and different colors are caused by varying thickness of oxide layers.
The cool thing about titanium weld colors is that they are predictable. In other words, we are able to determine what temperature the titanium metal reached when it was exposed to oxygen in the atmosphere.
The colors blue, violet, green, gray and white all happen at gradually higher temperatures.
There are some intermediate colors too and here is the progression..
The first titanium weld color is straw, followed by brown, then brownish blue, purple blue, green and blue, dull salmon pink, gray and white oxide.
Some Codes actually allow blue discoloration, but best practice is to prevent titanium welds from discoloring beyond the straw color.
Often times titanium welds are critical enough to hold the standards higher than the minimum allowed by a code.
But like I said at the start, even if you dont need to weld titanium, you can use this information to test the shielding gas coming out of your tig torch.
Titanium begins to discolor at around 500 degrees F. The hotter it gets without being protected by inert gas like argon, the more it oxidizes and changes colors beginning at straw and ending at white chalky oxide.
But when protected by argon until it cools below 500 deg F, titanium will be bright and silver even when heated past its melting point which is approximately 3135 F depending on the alloy grade.
What this means to you is that you can test the shielding gas coming out of your tig torch just by making a puddle and letting it cool and then evaluating the discolored titanium metal.
Here is how to do it…
Set your tig welding machine to about 50 amps for welding titanium. Set your post flow shielding timer to 15 seconds. Hold the tig torch at a dead nuts 90 degree angle to the titanium test piece and light up. Create a puddle about 1/4″ to 3/8″ , keep the arc as short as the diameter of the tungsten used, and dwell for around 7 seconds. Let off your foot pedal amperage control and hold the torch still until the weld and heated area cools completely…around 15 seconds.
If your argon is not contaminated, your electrode as well as the titanium puddle will be completely silver.
There will be a circular area around the puddle weld where the argon envelope shielding protected the titanium, that is discolored. That’s OK as long as it is symmetrical and at least as large as the inside diameter of the tig cup.
An odd shaped halo of titanium weld colors too close to the weld might indicate a clogged diffuser in the gas lens collet body or other problem…and if the weld puddle and electrode are not bright silver, you may have bad argon or a leak.
Things like that are very important to know before making a critical weld.