Use of a Toroidal Nozzle for Welding Duplex Stainless Steel.

The goal of this research was to determine the appropriate parameters for welding two-phase duplex stainless steel (DSS) and to understand the challenges involved in the process. For welding pipes with diameters of ø25 mm and ø38 mm of steel type 1.4462, the classic tungsten inert gas (TIG) method and TIG with a toroidal shielding gas nozzle were used. The aim was to improve the durability and service life of welded joints produced using the toroidal shielding gas nozzle compared to those produced using traditional TIG methods for DSS welding. The welding process was carried out using the parameters: arc voltage 9V, welding current 105A for TIG and 80A with a toroidal shielding gas, welding speed 90 mm/min for TIG and 95 mm/min with a toroidal shielding gas. The welded elements were tested for quality properties. Tests such as visual, penetration, radiographic, and destructive tests (macroscopic, ferrite content, hardness, microscopic, diffraction, static strength, and fatigue) were conducted on the test samples prepared in the TIG process. The actual test results were compared to the acceptable values from the standards. Using a toroidal nozzle in the welding process had lowered the ferrite content in the surface layers by about 10% in comparison to the traditional TIG method. The morphology and phase arrangement of the tested welded joints varied significantly, even when utilizing a toroidal nozzle. The analysis of the determined durability showed that welding with a toroidal shielding gas nozzle provided superior results, with enhancements ranging from 4% to 132%. Furthermore, the use of a toroidal nozzle reduced gas consumption by 17% for each joint type compared to conventional welding. In terms of service life, the joints welded with a toroidal nozzle demonstrated nearly twice the longevity of those welded with traditional methods. [ABSTRACT FROM AUTHOR]