Titanium Grade 12 is forged conventionally, within the narrow temperature range 815 – 900°C. Titanium and its alloys are generally more difficult to forge than both aluminium and alloy steels, due to their high strain rate sensitivity and rapid increase of strength with falling temperature. Hot forging leaves a thick, hard outer layer of titanium oxide on the surface. This layer is called “Alpha Case” and is usually removed by pickling in a mixture of nitric and hydrofluoric acids. As supplied, titanium alloys are usually annealed and pickled, and can be readily cold formed in conventional machines using standard methods. In cold forming the “alpha case” does not form and further pickling is not needed, except to remove any carbon steel embedded in the surface, which can cause pitting corrosion.
Titanium Grade 12 is readily machinable by conventional methods. Like stainless steel, titanium has a low thermal conductivity and heat dissipation is inhibited, so copious amounts of coolant should be used. Sharp carbide tools are used. Deep, continuous cuts are best.
Titanium Grade 12 is readily weldable by GMAW (MIG) and GTAW (TIG) processes. Preheat or post weld heat treatment are not needed. The area to be welded must beCLEAN, free from all grease and shop dirt, including marking pencil marks. A trailing gas shield is used in addition to the normal welding torch gas shield, to prevent heavy oxidation during cooling. Matching filler metal to AWS specification ERTi-12 is used. The gas shield must be low in hydrogen, oxygen and nitrogen, all of which readily dissolve in titanium and cause embrittlement.