W Lucas

Bio: W Lucas is an academic researcher. The author has an hindex of 1, co-authored 1 publication(s) receiving 99 citation(s).

Activating flux - increasing the performance and productivity of the tig and plasma processes

Abstract: This paper presents details of the A-TIG process and its operating characteristics. A mechanism is proposed by which the unique depth of weld pool penetration is achieved. Whilst there are undoubted significant productivity benefits to be gained, its performance in comparison to the conventional TIG plasma processes is highlighted and the potential areas of application are identified.

Performance of activated TIG process in austenitic stainless steel welds

Abstract: Five kinds of oxide fluxes, MnO 2 , TiO 2 , MoO 3 , SiO 2 , and Al 2 O 3 , were used to investigate the effect of activated tungsten inert gas (activated TIG) process on weld morphology, angular distortion, delta-ferrite content, and hardness of Type 316L stainless steels. An autogenous TIG welding was applied to 6 mm thick stainless steel plates through a thin layer of flux to produce a bead-on-plate welded joint. The oxide fluxes used were packed in powdered form. The experimental results indicated that the SiO 2 flux facilitated root pass joint penetration, but Al 2 O 3 flux led to the deterioration in the weld depth and bead width compared with conventional TIG process. Activated TIG welding can increase the joint penetration and weld depth-to-width ratio, thereby reducing angular distortion of the weldment. On the basis of the present results, it is considered that the centripetal Marangoni convection and constricted arc plasma as a mechanism in increasing the penetration of activated TIG joint.

TIG welding with single-component fluxes

Abstract: Gas tungsten arc welding is fundamental in those applications where it is important to control the weld bead shape and the metallurgical characteristics. This process is, however, of low productivity, particularly in the welding of large components. The activated flux TIG (ATIG) welding process, developed by the Paton Welding Institute in the 1960s, is now considered as a feasible alternative to increase the process productivity. ATIG welding uses a thin layer of an active flux that results in a great increase in weld penetration. This effect is, generally, connected to the capture of electrons in the outer parts of the arc by elements of high electronegativity, which constrict the arc causing an effect similar to that used in plasma arc welding. Generally, the literature does not present the flux formulations for ATIG welding, the few formulations that were found to have a complex nature. The present work evaluates the use of ATIG welding for the austenitic stainless steels with fluxes of only one major component. The changes in weld geometry were compared to variations in the electrical signals from the arc and the arc shape. The effect of the flux on the weld microstructure was also studied. The results indicate that even the very simple flux that was used can greatly increase the penetration of the weld bead.

Study of the characteristics of duplex stainless steel activated tungsten inert gas welds

Abstract: The purpose of this study is to investigate the effects of the specific fluxes used in the tungsten inert gas (TIG) process on surface appearance, weld morphology, angular distortion, mechanical properties, and microstructures when welding 6 mm thick duplex stainless steel. This study applies a novel variant of the autogenous TIG welding, using oxide powders (TiO 2 , MnO 2 , SiO 2 , MoO 3 , and Cr 2 O 3 ), to grade 2205 stainless steel through a thin layer of the flux to produce a bead-on-plate joint. Experimental results indicate that using SiO 2 , MoO 3 , and Cr 2 O 3 fluxes leads to a significant increase in the penetration capability of TIG welds. The activated TIG process can increase the joint penetration and the weld depth-to-width ratio, and tends to reduce the angular distortion of grade 2205 stainless steel weldment. The welded joint also exhibited greater mechanical strength. These results suggest that the plasma column and the anode root are a mechanism for determining the morphology of activated TIG welds.

Comparison of TIG welded and friction stir welded Al–4.5Mg–0.26Sc alloy

Abstract: This paper investigates the comparative microstructural and mechanical characteristics of fusion welds (TIG) and solid-state welds (FSW) of Al-4.5 Mg-0.26 Sc heat-treatable aluminium alloy Microstructures of base metal and welded zones are analyzed by optical (OM) and transmission electron (TEM) microscopy Particular emphasis is laid on the evolution of hardening precipitates in welded areas. The corresponding mechanical properties are evaluated through microhardness measurements and uniaxial tensile tests. The effect of a post-weld heat treatment on both microstructure and mechanical properties is further examined. The results suggest that hardening precipitates are comparatively more affected by the TIG than by the FSW process. This results in a substantial reduction of mechanical properties of TIG welds that can be partially recovered through a post-weld heat treatment.

Effects of shielding gas composition and activating flux on GTAW weldments

Abstract: This study investigated the effects of shielding gas composition and activating flux on weld morphology, angular distortion, retained delta-ferrite content, mechanical properties and hot cracking susceptibility. An autogenous gas tungsten arc welding process was used on austenitic stainless steel to produce a bead-on-plate weld. The nitrogen content in the argon-based shielding gas was in the range of 2.5–10 vol.%. Activating flux materials consisted of a manganese oxide powder and zinc oxide powder mixture. The results showed that the penetration and cross-sectional area of the weld increased with the increase of nitrogen added to the argon-base shielding gas. An increase in shielding gas nitrogen content had markedly reduced the angular distortion of the weldment. Increasing the nitrogen increased the tensile strength and hardness but reduced the retained delta-ferrite. The hot cracking susceptibility of the austenitic stainless steel welds increased as the nitrogen content increased. Activating flux plays a major role than nitrogen added in argon shielding gas, which influenced the various properties of austenitic stainless steel TIG welds.