Weld Purging of Titanium joints.
Correct weld purging of Titanium 
is possibly more critical than with most other metals.
At least two major elements are of utmost importance in Weld Purging Technology, to make successful welds:
1.0 A good source of weld purge gas for welding Titanium.
Welding gas suppliers all have special high quality grades of Argon, which is the most widely recommended gas for back purging Titanium. Typical grades are 99.9995% which is 5 parts per million of impurities, including oxygen. (Helium can also be used, however because of its density, it tends to go upwards risking inadequate purging).
2.0 Â A good instrument to measure the Oxygen level in the weld purge gas as it exits the purged volume
Part of the correct weld purging procedure is to ensure that the oxygen level in the exiting weld purge gas is held at 10 parts per million or lower and maintained throughout the weld.
This is best achieved by using a Weld Purge Monitor® that can measure down to 10 parts per million and one that preferably can switch the weld set off or send out a warning signal in the event of Oxygen levels rising too high.
The Titanium welding process should not begin until the oxygen level in the exiting weld purge gas is shown accurately to be about 10 ppm.
The Titanium joint being welded must continue to be purged after welding has finished until the temperature drops below 420ºC (800°F) approximately. (The welding procedure will give the precise figure for each application).
Information about the welding of Titanium can be found under the Ref: AWS D1.9, Structural Welding Code—Titanium.
The skill of welding Titanium is not discussed here, but can be found under the reference:
http://www.millerwelds.com/resources/articles/TIG-gtaw-titanium-welding
Further information about the weld purging of Titanium joints can be obtained by emailing: rasewell@huntingdonfusion.com
Titanium 101: Best TIG (GTA) Welding Practices millerwelds.com
Pretty colors are fine for titanium jewelry. However, blue, violet, green, grey and white colors indicate atmospheric contamination in a GTA welded titanium  component. In critical applications, welds exhibiting such colors
