Welding titanium Grade 2 for piping systems demands rigorous atmospheric protection to prevent contamination. Oxygen, nitrogen, and hydrogen pickup above 300°C embrittle the weld and degrade corrosion resistance. The solution lies in two critical elements: backing gas and trailing shield.
For the root pass, argon purging of the pipe interior is mandatory. A common target is maintaining oxygen levels below 50 ppm inside the pipe. This is achieved through pre-purge time and a positive argon flow during welding. For the cover and fill passes, a trailing shield extends the inert gas coverage over the cooling weld bead. The shield must be sized to cover the entire HAZ until the temperature drops below 300°C.
Auditors and inspectors typically check three things: the purity of the argon supply (99.99% minimum), the flow rate and delivery system for the backing gas, and the design of the trailing shield relative to weld travel speed. A shield that is too short or poorly shaped can leave the weld vulnerable.
Proper gas coverage is not optional for titanium piping. It determines whether the weld meets mechanical and corrosion requirements.
What methods do you use to verify trailing shield effectiveness before production?