Comparison between PCA analysis and Grey based Taguchi analysis of TIG welding process parameters on Duplex stainless steel

Achieving optimal mechanical properties in welding joints hinges on employing precise parametric conditions. This is particularly crucial for Tungsten Inert Gas (TIG) welding of ASTM/UNS 2205 Duplex Stainless Steel (DSS), where attributes like hardness, ultimate tensile strength, and yield strength are paramount. Maintaining high Hardness Value (HV) demands proper welding parameters such as welding current, gas flow rate, and welding speed. To enhance DSS welding quality, especially hardness, this study utilizes the Taguchi method to optimize welding process parameters. The importance of each factor is assessed through Annova statistical analysis. The outcomes highlight the positive impact of parametric optimization on HV, as evidenced by the analysed data. Parametric optimization proves to be a potent approach for refining industrial processes like welding, with particular relevance in TIG welding of duplex stainless steel due to its mechanical robustness and corrosion resistance. Nevertheless, challenges arise due to the material's elevated hardness and low thermal conductivity, resulting in potential defects like cracks and porosity. The identification of optimal welding parameters, encompassing current, voltage, speed, and gas flow rate, helps address these challenges and advances high-quality welds. Through systematic variations and analysis of these parameters, researchers and engineers can pinpoint the optimal combination that mitigates defects while maximizing desired joint attributes. Within the realm of TIG welding of duplex stainless steel, metric optimization holds the potential to elevate welding quality, curtail costs and waste, and heighten productivity and safety. Consequently, organizations can attain enhanced performance, efficiency, and profitability within their welding processes

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively.

Welded stainless steel components used in power plants and chemical industries are subjected to mechanical load cycles at elevated temperatures which result in early fatigue failures. The presence of weld makes the component to be liable to failure in view of residual stresses at the weld region or in the neighboring heat affected zone apart from weld defects. Austenitic stainless steels are often welded using Tungsten Inert Gas (TIG) process. In case of single pass welding, there is a reduced weld penetration which results in a low depth-to-width ratio of weld bead). If the number of passes is increased (Multi-Pass TIG welding), it results in weld distortion and subsequent residual stress generation. The activated flux TIG welding, a variant of TIG welding developed by E.O. Paton Institute, is found to reduce the limitation of conventional TIG welding, resulting in a higher depth of penetration using a single pass, reduced weld distortion and higher welding speeds. This paper presents the fatigue crack growth rate characteristics at 823 K temperature in type 316LN stainless steel plates joined by conventional multi-pass TIG (MP-TIG) and Activated TIG (A-TIG) welding process. Fatigue tests were conducted to characterize the crack growth rates of base metal, HAZ and Weld Metal for A-TIG and MP-TIG configurations. Micro structural evaluation of 316LN base metal suggests a primary austenite phase, whereas, A-TIG weld joints show an equiaxed grain distribution along the weld center and complete penetration during welding (Fig. 1). MP-TIG microstructure shows a highly inhomogeneous microstructure, with grain orientation changing along the interface of each pass. This results in tortuous crack growth in case of MP-TIG welded specimens. Scanning electron microscopy studies have helped to better understand the fatigue crack propagation modes during high temperature testing.

Tungsten inert gas (TIG) welding is extensively employed for joining steel products in several manufacturing fields, partly thanks to the high mechanical weld quality achievable. However, the low efficiency represents its main drawback in industrial applications. A high-productivity alternative is the keyhole TIG method. This research is aimed at investigating and comparing the metallurgical characteristics and mechanical quality of single-pass keyhole TIG welding and conventional multi-pass TIG technique for welding medium-thickness steel parts. For this purpose, the two welding techniques were employed for joining 10-mm-thick 316L austenitic stainless steel plates. The influence of the welding processes on the metallurgical and mechanical characteristics of the joints was investigated through microstructural analysis, hardness measurements as well as tensile, bending and impact tests. Furthermore, the fracture surfaces after tensile and impact tests were analysed using scanning electron microscopy technique. The results reveal sound and defect-free welds with a dendritic weld zone microstructure consisting of a matrix of austenite and δ-ferrite, with a reduction of the latter in keyhole mode welding. Hardness measurements resulted slightly lower in the weld zone produced through the keyhole technique than those achieved by conventional TIG, while the weld tensile and bending strength properties were comparable. Moreover, keyhole TIG welding revealed excellent fracture toughness properties in the weld zone, even better than those of conventional TIG technique. Fractographic analysis of the joints showed a ductile fracture mechanism in both welds. Finally, experiments prove a drastic reduction in welding time by employing the keyhole TIG technique compared with conventional TIG, as well as a significant saving on welding consumables.

Study on microstructure and mechanical properties of 304 stainless steel joints by TIG, laser and laser -TIG hybrid welding

In this work, one-pass and two-pass friction stir processing (FSP) were applied to the tungsten inert gas (TIG) weldments of AA6082-T651 and AA8011-H14 to analyse the microstructure and tensile characteristics of the weldments. The tests included macrostructure, microstructure, microhardness, tensile testing and fractography. When the one-pass and two-pass FSP were applied to the TIG weldments, the coarse grain structure (grain size 24.63 µm) was transformed into a refined grain structure (grain size 2.632 µm for second pass), thereby eradicating the defects that had been seen before FSP. The tensile strengths of the TIG + FSP passes were more significant than that of the TIG welded joints. The ultimate tensile strength of TIG welding, TIG + FSP 1-pass and TIG + FSP 2-pass were 86.86 MPa, 133.833 MPa and 135.75 MPa, respectively. The tensile strain of the TIG + FSPed joints was found to have a minimal difference from that of the TIG welded joints, with the TIG joint with a higher percentage. The joints’ microhardness post-FSP was more significant than the TIG weldment. The maximum hardness (73.84 HV) at the Nugget zone (NZ) was observed in the TIG + FSP 2-pass welded joint. The results obtained corresponded with the grain sizes of the welded joints; the TIG results displayed a coarse-grained structure, while the TIG + FSP results, regardless of the passes, showed a fine sandwich-arranged grain structure.

Mechanical and corrosion properties of TIG welded dissimilar AISI 420 and UNS S32205 stainless steel sheets

An Analysis of the Mechanical Behavior of AISI 4130 Steel after TIG and Laser Welding Process

Sampling and Analysis of Welding Fumes and Gases Produced Under Experimental Hyperbaric Conditions

Electron beam melting (EBM) is a powder bed additive manufacturing (AM) technology for small and medium-sized Ti-6Al-4V components. In this study, EBM-built Ti-6Al-4V tensile specimens were joined using tungsten inert gas (TIG) welding and laser beam welding (LBW) to form large-scale components. Weld morphology, defects, mechanical properties, and microstructure of joints made by LBW and TIG welding were compared. It was found that the pore sensitivity of EBMed Ti-6Al-4V is extremely high. In EBM, the most common defect is pores, but this has been ignored as parts are broken at welding zone. Large pores are distributed along the edge of the weld in TIG welding, whereas in laser welding they are distributed at top of the weld. LBW has a much smaller grain size in the weld center than TIG welding. The TIG welded sample has more heat at the weld boundary. Mechanical properties of TIG welded parts were superior to laser welded parts. The main reason for this is that the weld cross section is larger than the center. In addition, in the microstructure examination of TIG welding, it was observed that the weld had fewer defects than laser welding. Also, the elongation of all specimens is very low.

GTAW welding (gas tungsten arc welding) or commonly called TIG (tungsten inert gas) welding is welding using a flame arc produced by a fixed electrode made of tungsten. One thing that needs to be considered in welding (especially in TIG welding) is the effect of welding amperage on the mechanical properties or strength of the welded joint. PeThe tests carried out in this study were tensile tests and micro tests. Tensile tests were carried out with the aim of knowing the tensile strength of the test specimens. And the micro test is carried out aiming to see the microstructure that occurs in the weld area (HAZ). Data analysis was carried out by looking at the relationship of tensile stress, yield stress, and strain that occurred in the test specimen based on variations or parameters used during welding. Based on the analysis of the mechanical properties and microstructure of thematerial stainless steel sus 304 musing TIG welding (Tungsten Inert Gas)with a current variation of 80 A, 100 A and 120 A showed a difference that caused a comparison of the difference in the tensile strength. Welding using a current of 80 A has the highest average stress of 316.6 kN/mm2, welding using a current of 100 A has a tensile strength of 378.6 kN/mm2. While welding using a current of 120 A has the highest tensile strength of 458.3 kN/mm2. The results of this test indicate that the analysis of the mechanical properties and microstructure of TIG welding (Tungsten Inert Gas) shows a significant effect of tensile strength at a current of 120 A, so it has the highest tensile strength with an average value of 458.3 kN/mm2

This study tackles the challenges of inconsistent weld quality and limited real-time monitoring in Tungsten Inert Gas (TIG) welding by developing a digital twin for the process. The primary objective is to enhance process efficiency and quality control by creating a high-fidelity virtual model of TIG welding that enables real-time monitoring and control. To achieve this, the study employs Desirability Function Analysis (DFA) to optimize multiple quality characteristics. The methodology integrates advanced sensors and IoT technologies to gather real-time data on critical welding parameters such as current, voltage, travel speed, and gas flow rate. This data is used to create a simulation model that accurately replicates the physical welding process. The experiments are conducted using digital twin on SS304 thin which is widely used in industrial applications. By applying DFA, the study converts multiple quality characteristics into a single composite desirability score, offering a quantitative assessment of process efficiency and output quality. The experimental results demonstrate the digital twin’s ability to accurately predict and control welding outcomes, significantly improving productivity and quality control. This research highlights the transformative potential of digital twin technology in TIG welding, paving the way for smarter, data-driven decision-making in industrial settings.

An extensively studied Al-Mg-Si (AA6061) alloy has been considered for this investigation. This alloy is used for large number of industrial applications since it possesses medium to high strength to weight ratio, excellent weldability and corrosion resistance. It has been observed that these alloys are usually used in sheet form and were welded for large application. Even though a number of welding procedures are available, the most convenient and economical procedure of tungsten inert gas (TIG) welding was used to weld Al-Mg-Si sheets. All the sheets were having a thickness of 3.0 mm. In the case of single pass TIG welded samples, the pulsed current has been found beneficial as it is most advantageous over the conventional continuous current process. The use of pulsed current parameters has been found to improve the mechanical properties of the welds compared to those of continuous current welds of this alloy. This is possibly due to the grain refinement occurring in the fusion zone. These results clearly demonstrated that current parameters and its optimization is most important aspect for obtaining a good weldment. An Influence of process parameters and their influence on mechanical properties are explained in detail in light of microstructural details.

Reduced-activated ferritic-martensitic steels are being considered for use in fusion energy reactor and subsequent fusion power reactor applications. Typically, those reduced activated steels can loose their radioactivity in approximately 100 years, compared to thousands of years for the non-reduced-activated steels. The commonly used welding process for fabricating this steel are electron-beam welding, and tungsten inert gas (TIG) welding. Therefore, Activated-flux tungsten inert gas (A-TIG) welding, a variant of TIG welding has been developed in-house to increase the depth of penetration in single pass welding. In structural materials produced by A-TIG welding process, weld bead width, depth of penetration and heat affected zone (HAZ) width play an important role in determining in mechanical properties and also the performance of the weld joints during service. To obtain the desired weld bead geometry, HAZ width and make a good weld joint, it becomes important to set up the welding process parameters. The current work attempts to develop independent models correlating the welding process parameters like current, voltage and torch speed with weld bead shape will bead shape parameters like depth of penetration, bead width, HAZ width using ANFIS. These models will be used to evaluate the objective function in the genetic algorithm. Then genetic algorithm is employed to determine the optimum A-TIG welding process parameters to obtain the desired weld bead shape parameters and HAZ width.

04/00550 SLLV phase behavior and phase diagram transitions in asymmetric hydrocarbon fluids: Shaw, J. M. and Béhar, E. Fluid Phase Equilibria, 2003, 209, (2), 185–206.