ABSTRACT
For the manufacture of seamless pipes and tubes are used, as raw materials, hollow bars from hot deformation processes like extrusion and rotary tube piercing (Mannesmann process). Starting from these semi-elaborated products and by means of successive cross sections reductions through tube drawing or tube rolling (cold pilgering) the requested final dimensions are achieved. The rotary tube piercing process, Mannesmann process, includes drilling cylindrical billet through a progressive diametral compression that generates a crack at the center and facilitates perforation along the oblique transverse rolling. In contrast, the extrusion is a compression process in which the metal is forced to flow through a die to shape cross section. This characterization work was performed on semifinished products from both processes, extrusion and rotary tube piercing in titanium alloys (Titanium Gr. 2 (Titanium Commercially Pure) and Titanium Gr. 5 (Ti-6Al-4V)). Destructive tests (tensile test, flattening test and flaring test) non-destructive tests (visual inspection, boroscopy, dimensional, surface roughness and discontinuity determination by dye penetrant) and metallogra-phy (macro and micro) were performed. Chemical contamination caused by the furnace atmosphere was also assessed. Finally, the characteristic defects from each deformation process, their root cause and possible solutions were discussed.
Keywords:
Hot deformation; Rotary tube piercing; Extrusion; Titanium alloys
