Development of Thick-Section Commercially Pure Titanium Welds using Gas Tungsten Arc Welding Process

Commercially pure titanium plates of 50 mm thickness were joined using a titanium filler material by employing gas tungsten arc welding (GTAW) technique. Double-V edge configuration was used for this work. This technique provides ease and comfort of welding thick-section titanium plates using manual conventional fusion welding process. The novelty of this welding procedure establishment lies in the design of a unique gas shielding fixture around the torch. This gas shielding fixture consists of a central hole for inserting the torch surrounded by a ceramic cup. The ceramic cup contains two inlet tubes for supplying shielding argon and a metallic cap containing several perforations toward the welding side of the fixture for supply of shielding gas. This gas shielding fixture not only provides shielding of the weld pool from oxidation but also acts as a heat sink, thereby reducing the temperature of welded fusion zone, thus enabling continuous welding with readily acceptable visual color. These welded plates were then characterized to reveal various zones and phases present in each zone. Phases and their morphology present in these zones were identified and correlated with the welding procedure. The welds were qualified as per ASME Section IX by conducting bend tests, tensile, and impact tests. Fractographic analysis of tensile samples indicates the presence of ductile features obtained from void coalescence, while that of impact samples at various zones indicates the presence of both ductile and brittle features. The nature of fracture surface evolution in the mechanical tests was explained on the basis of strain rate and microstructural features.