WELDING TITANIUM

In general, welding of titanium and its alloys can be readily performed, but it is necessary to exclude reactive gases, including oxygen and nitrogen from the air, and to maintain cleanliness. Thus weld properties are heavily influenced by welding procedures, especially by the adequacy of inert gas shielding.

The GTAW (gas tungsten arc welding) process is common, although GMAW (gas metal arc welding), friction welding, laser welding, resistance welding, plasma arc welding, electron beam welding, and diffusion bonding are all used in some cases. Both alloy composition and microstructure are important in determining weldability, with the presence of beta phase having a deleterious effect.

Unalloyed titanium and alpha alloys are generally weldable and welded joints generally have acceptable strength and ductility. Postweld stress-relief annealing of weldments is recommended. Some alpha-beta alloys, specifically Ti-6Al-4V, are weldable in the annealed condition as well as in the solution treated and partially aged condition (aging can be completed during the post-weld heat treatment). Strongly stabilized alpha-beta alloys can be embrittled by welding, the result of phase transformations occurring in the weld metal or the heat affected zone. Some beta alloys are weldable in the annealed or the solution treated condition.