Current TIG Research Articles

Parametric investigation on surface responses of TIG cladded medium carbon steel substrate with TiO2–SiC powder

The present research work consists of surface modification of a medium-carbon steel substrate with TiO2–SiC powder of the same weight percentage. A Taguchi L9 orthogonal array was used for the design of experiments. Different input process parameters, such as current (A), scan speed (mm/s) and gas flow rate (L/min), have played a significant role in controlling geometrical surface responses. The relationship between different input parameters and response surfaces (clad height, clad width) was plotted and discussed. Diagrams have been utilized to demonstrate the combined impacts of any two process factors on clad height and clad width, such as TIG current–scan speed, TIG current–gas flow rate and gas flow rate–scan speed. Experimental observations revealed that cladding input parameters have a significant influence on response surfaces. TIG current has the maximum impact on clad height. Observations showed that with the increment of current up to a certain amount clad height increased. It was also observed that with an increment of current, clad width increases. Observations revealed that as the gas flow rate rises, clad height decreases but clad width increases. It was further noted that with an increase in scan speed, clad height and clad width follow a downward trend.

Prediction of the keyhole TIG welding-induced distortions on Inconel 718 industrial gas turbine component by numerical-experimental approach

Welding technologies represent a paramount joining process for ensuring the quality and reliability of critical industrial components; therefore, their innovation constitutes a driving force in realizing increasingly competitive products. A recently developed technology is the keyhole TIG welding, a new high energy–density alternative to the conventional TIG process. A key role in improving innovative manufacturing processes such as the keyhole TIG is covered by numerical simulation; indeed, it allows the development of a process digital twin able to support decisions and work as a predictive tool. Within this framework, the paper deals with the numerical-experimental investigation of the keyhole TIG technology, successfully employed on a simplified mock-up of an industrial gas turbine component consisting of two 6.5-mm-thick Inconel 718 rings. Numerical analysis aimed at predicting welding-induced distortions was performed employing two different computational approaches, namely the moving heat source and the simplified imposed thermal cycle methods. The numerical-experimental comparison of the results demonstrates an innovative approach in the field of the current keyhole TIG numerical simulation since, besides verification of numerical thermal analysis, further substantial validation of the post-weld distortion predictions is provided through comprehensive three-dimensional experimental data. Moreover, the comparative assessment of the two computational approaches and experimental evidence revealed that the imposed thermal cycle method implementation does not compromise the accuracy of welding distortion forecasting in industrial applications such as that investigated. Therefore, it can be regarded as a valuable tool for supporting the process engineer in designing the ideal set-up to comply with a variety of industrial requirements, among them strict design tolerances.

Impact of CC and PCTIG Welding on SMO 254 Joints Using Alloy 625 Filler

Objectives: This investigation analyzes the microstructure, mechanical and corrosion characteristics of SMO 254 joints welded using constant current TIG (CCTIG) and pulse current TIG (PCTIG) with alloy 625 (ERNiCrMo-3) filler metal. Method: Optical microscopy and SEM with EDAX were employed for microstructural characterization and phase analysis. Mechanical properties were assessed through Vickers microhardness, tensile, and Charpy impact tests, followed by fracture analysis. Findings: EDAX point analysis indicates reduced Mo segregation and the absence of Nb segregation in PCTIG weldments. The overall corrosion resistance remains acceptable despite a slightly higher corrosion rate in PCTIG weldments. The study highlights the superior mechanical properties and microstructural control achieved with PCTIG welding, making it a preferable technique for SMO 254 joints. Novelty: Notably, the research establishes PCTIG as a superior method for welding SMO 254, demonstrating that it not only refines the grain structure but also significantly enhances mechanical properties, particularly toughness, by 50% compared to CCTIG. Keywords: SMO 254, SASS, Microstructural characterization, Mechanical properties, CCTIG, PCTIG

Modeling of heat transfer and fluid flow in the metal being welded during DC and HFPC TIG spot welding

A mathematical model of non-stationary electromagnetic, heat and mass transfer processes in the metal during high frequency pulsed current (HFPC) TIG spot welding has been proposed. A computational algorithm for the the numerical solution of the corresponding mathematical problems has been developed and implemented in Wolfram Language. A comparative analysis of the hydrodynamic and heat transfer processes in the specimen of steel S-235JR during HFPC TIG welding with 10 kHz square wave pulse current modulation and direct current (DC) TIG welding with current equal to the mean current of HFPC mode has been carried out. As simulations showed, the HFPC modulation results to appreciable weld penetration with minor influence on the radius of the fusion zone compared to the DC process.

Metallurgical, mechanical and corrosion behavior of Interpulse and pulsed current TIG dissimilar welds of Monel 400 and AISI 316L

This research work explores the weldability, structural integrity, mechanical properties, and corrosion behavior of dissimilar welds of Monel 400 and AISI 316L developed by using Interpulse and pulse arc current modes in TIG welding process. ERNiCrMo-3 filler of 1.6 mm was used to fill the V-groove configuration of 5 mm thick plates in multiple passes. Metallurgical changes were observed in both Interpulse and pulsed current dissimilar weldments using optical and scanning electron microscope techniques. Mechanical properties of the joined structures were evaluated by performing tensile tests on UTM and hardness measurements on weld surfaces using Vickers hardness tester. The resistance against the corrosion especially at the weld area of both welded structures was measured using a cyclic sweep test. From the XRT and visual inspection analyses, the joined structures were free from defects and also seen the uniformity of the filler distribution toward the base metals. The grain structure with well-defined grain structures were identified in PC-TIG weldments whereas fine grains with clear distribution of filler alloying elements were seen in Interpulse-TIG weldments. Interpulse-TIG weldments exhibited with better mechanical and corrosion resistance properties than the PC-TIG weldments vowing to constricted arc mode during the welding process.

Characterization of an energy efficient pulsed current TIG welding process on AISI 316 and 304 stainless steels

This paper presents the characterization of a TIG welding process carried out by means of an arc welding power supply able to provide dc or pulsed current. The arc welding power supply is based on resonant power converters and an FPGA-based control circuit. Dc and multiple pulsed operations up to 1 kHz with different pulse widths have been tested. The operation of the proposed welding power supply has been compared to that of a high-quality commercial welding machine. Regarding performance, the investigated electrical parameters are: power factor, power conversion efficiency and the energy consumption of the process. The radiography and mechanical properties of the welds have been examined. The mechanical properties of the welded joints characterized through tensile tests are the yield stress, tensile strength and the strain under maximum stress. In addition, the impact properties of the joints were determined through Charpy tests and the curves relating energy absorbed and temperature were obtained. The results show an improved performance of the proposed arc welding power supply over the commercial counterpart, with higher efficiency and power factor, as well as lower energy consumption. The yield stress and tensile strength results indicate that the welded plates using pulsed modes with the proposed power supply are comparable to the reference weld performed with dc operation using the commercial welder. Remarkably, it was observed that the ductility of the welded plates using pulsed modes with the proposed power supply outperforms those of the reference weld carried out with dc arc using the commercial welder.

Effect of post weld heat treatment on weld metal microstructure and hardness of HFCA-TIG welded ASTM-B670 high temperature alloy joints

In this investigation, the effect of post weld heat treatment (PWHT) conditions on weld metal (WM) microstructure and hardness of ASTM B670 alloy joints are studied for gas turbine engine applications. This high temperature alloy was joined using high frequency compressed arc TIG (HFCA-TIG) welding process. The precipitation hardening was performed on ASTM-B670 alloy joints directly after welding (DPH); after solutionizing the welds at 980 °C (980ST+PH) and at 1065 °C (1065ST+PH). The WM of ASTM-B670 alloy showed better response to PWHT in minimizing the Laves phases and enhancing the WM hardness of joints. The DPH, 980ST+PH and 1065ST+PH joints showed 55.63%, 58.80% and 64.08% enhancement in hardness of WM compared to as welded (AW) joints owing to the precipitation of hardening phases after PWHT. The 1065ST+PH joints revealed higher hardness of WM than DPH and 980ST+PH joints It is attributed to the complete dissolution of Laves phases in WM causing more Nb available for precipitation hardening of WM. Nevertheless, the PM hardness of 1065ST+PH joints are lower than 980ST+PH joints owing to the severe grain growth. The HFCA-TIG welds showed volume fraction of Laves phase up to 5.10% in WM which is 80.38% and 36.25% lower than constant current TIG (CC-TIG) and pulsed current TIG (PC-TIG) welds. It is attributed to magnetic compression and high frequency pulsation of arc which minimizes input of heat in welding and offers greater refinement of WM.

Pulsed TIG Cladding of a Highly Carbon-, Chromium-, Molybdenum-, Niobium-, Tungsten- and Vanadium-Alloyed Flux-Cored Wire Electrode on Duplex Stainless Steel X2CrNiMoN 22-5-3

The hardfacing process aims to increase the life span of structural components in the petrochemical, mining, nuclear and automotive industries. During operation, these components are subject to demands of abrasion wear, cavitation erosion and corrosion. Duplex stainless steels are characterized by high mechanical characteristics and corrosion resistance, but poor behavior to abrasive wear and cavitation erosion. The improvement in wear resistance is possible by selecting and depositing a special alloy on the surface using a joining technique that ensures a metallurgical bonding between the layer and the substrate. The experimental investigations carried out in this work demonstrate the ability of the TIG pulsed welding process to produce layers with good functional properties for engineering surfaces. The “Corodur 65” alloy was deposited on a duplex-stainless-steel substrate, X2CrNiMoN22-5-3, using a series of process parameters that allowed for the control of the cooling rate and heat input. The properties of the deposited layers are influenced not only by the chemical composition, but also by the dilution degree value. Since the deposition of layers through the welding operation can be considered as a process with several inputs and outputs, the control of the input parameters in the process aims at finishing the granulation and the structure in the fusion zone as well as limiting the segregation phenomena. The aim of this work is to investigate the microstructural characteristics of the iron-based alloy layer, Corodur 65, deposited via pulsed current TIG welding on duplex X2CrNiMoN22-5-3 stainless-steel substrates.

Metallurgical, mechanical and corrosion behaviour of pulsed and constant current TIG dissimilar welds of AISI 430 and Inconel 718

This research work explore the weldability, structural integrity, mechanical properties and corrosion behaviour of dissimilar welds of Inconel 718 and AISI 430 developed by using constant and pulse arccurrent modes in TIG welding process. The welded structures defects for inspected by employing X-ray radiography images as well as macrostructures. Metallurgical changes were observed using optical & scanning electron microscope techniques. Mechanical properties of the joined structures were evaluated by performing tensile test on UTM and hardness measurements on weld surfaces using Vickers hardness tester. The resistance against the corrosion especially at the weld area of both welded structures was measured. The joined structures were free from flaws and also seen the uniformity of the filler distribution towards the base metals. The grain coursing with well-defined grain structures were identified in CC-TIG weldmentswhereas fine grains with clear distribution of filler alloying elements were seen in PC-TIG weldments. PC-TIG weldments exhibited with better mechanical and corrosion resistance properties than the CC-TIG weldments vowing to pulse arc mode during welding process. The aerospace and nuclear industries will benefit from the study's findings especially turbine disc and shaft assembly.

Increase in Mechanical Properties and Damping Capacity of a Cast Mn-Cu Damping Alloy Welded Joint by Pulsed Current TIG Welding

Increase in Mechanical Properties and Damping Capacity of a Cast Mn-Cu Damping Alloy Welded Joint by Pulsed Current TIG Welding

Simulation of the influence of welding parameters on weld pool behavior during a TIG-MIG hybrid welding process

TIG-MIG hybrid welding produces better weld formation than traditional MIG welding at higher welding speeds. The adaptive heat source and arc pressure models of inclined TIG-MIG arcs on curved surface were improved based on their distribution on flat surface. A 3D transient model of heat and mass transfer in a weld pool was established to analyze the influences of various welding parameters on a high-speed TIG-MIG hybrid welding process. The influence of the TIG current, distance between electrodes, and welding speed on this hybrid welding process were simulated to study the quantitative relationships between process parameters, molten pool behavior, and weld beam formation. The heat flux field, temperature field, and fluid flow on the upper surface and longitudinal sections of the weld pool were simulated and analyzed under various welding conditions. Experiments were performed; the simulation results agreed well with the experiments.

INFLUENCE OF VOLTAGE AND CURRENT ON THE ARC SHAPE IN CABLE-TYPE WIRE TIG-MIG HYBRID WELDING

In order to achieve high efficiency, energy saving and high quality of welding, it is necessary to carry out research on cable-type wire TIG-MIG hybrid welding. In this study, voltage and current influences on the arc shape in cable-type wire TIG-MIG hybrid welding were studied. The results showed that in cable-type wire TIG-MIG hybrid welding, with an increase in the TIG current, the MIG current increased at first and then remained constant, while the MIG basic voltage remained unchanged. With an increase in the MIG voltage, the TIG current produced small changes, but overall, it remained stable. The TIG current of different droplet-transfer modes had different effects.

Numerical and Experimental Investigation of Heat Distribution and Residual Stress Variation on Stacked Thin Sheets of CRNO Electrical Steel Post Tungsten Inert Gas and Cold Metal Transfer Welding

Abstract The paper presents a numerical and experimental investigation on the stacking of thin, cold rolled nongrain-oriented (CRNO) electrical steel sheets post-tungsten inert gas (TIG) and cold metal transfer (CMT) welding for predicting the effects of TIG and CMT welding current on weld geometry, temperature field, and residual stress distribution in thin, stacked weld sheets. Numerical simulation of a transient nonlinear thermal three-dimensional (3D) element based on actual weld conditions was carried out using ansys software by employing a moving heat source model based on a 3D Gaussian distribution to predict changes in temperature. As a result of the thermal history provided by the model, a mechanical analysis is performed to determine the residual stress distribution and the surface distortion in the element. A significant increase in weld penetration and weld width of the samples was observed with the increase in welding current, as well as a change in the temperature field in the weld zone. Moreover, both the experimental and numerical data are consistent in their estimation of the generation of residual stresses in the weld samples. A numerical model is presented for predicting the thermomechanical behavior of TIG and CMT welded stacked CRNO structures in the stator core of electric motors.

Microstructure characterization and texture evolution of Ti-6Al-4V cladding layer fabricated by alterative current assisted TIG

In this paper, an alternating current (AC) was added to filling wire in the arc deposition process. The effect of alternative current on grains size and microstructure of Ti-6Al-4V cladding layers were studied. The microstructure evolution, grain size distribution, texture, and crystal twining of cladding layers with the addition of alternative current were studied in detail using metallographic microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscope (TEM). The results reveal that the addition of AC can effectively inhibit β grain growth, the grains size decrease with the increase of AC value. The enhancement of microstructure uniformity and decrease of texture intensity have been realized by electromagnetic force produced by alternative current. Additionally, the {10-10}<10-12> compression twins system was observed in cladding layer at 45A. • A new method of alternative current assistedTIG welding (AC-TIG) was used to fabricate Ti-6Al-4V cladding layer. • The microstructure uniformity and texture intensity decrease will realize under the coupled magnetic-thermal field. • The {10-10}<10-12> compression twins was identified by TEM characterization in cladding layer when AC value is 45A.

Variants of TIG welding process for improvement of weld penetration depth - A review

This article deals with the various process modifications that occurred in the tungsten inert gas welding process over a decked of time. The conventional TIG welding process usually offers a shallow weld penetration (up to 5 mm). Due to this limited depth of penetration, the industrial applications of this process are very limited and used only for sheet metal working. This article focuses on the various modification that has been made in the conventional TIG welding process to improve the process capabilities. Mainly flux assisted TIG welding, pulse current TIG welding, keyhole TIG welding, multi-electrode TIG welding, TIP-TIG welding process, and their hypothesis responsible to improve the weld penetration were discussed. The effect of various process parameters of these process variants on weld penetration was also discussed. So, this article will help in strengthening the future research trend in TIG welding for enhancement of its industrial application and capability of the process.

Effects of different laser power and welding speed on the microstructure and mechanical properties of TRIP joints in laser-TIG arc hybrid lap filler wire welding

The TRIP steel applied in the automotive application was welded successfully by hybrid low-power laser-TIG arc lap welding method with the Fe-based filler wire. The influence of different laser powers and different welding speeds on the forming properties of joints was studied. The introduction of the laser increased the heat input and the weld depth of the joint. The pulse laser stirred the weld seam and improved the formation of the joint. At a welding speed of 1500 mm/min, the defect-free lap joint of TRIP steels was obtained. The fracture occurred on the base metal. Compared with low current TIG welding, with the introduction of laser, the fracture form changes from brittle fracture characteristic to ductile fracture characteristic. The microstructure was mainly composed of pearlite, bainite, ferrite, and cementite. Pearlite and bainite are the strengthening phases. The microstructure evolution model of joints that varied with laser power and welding speed was established.

Thermal field and residual stress analyses of similar and dissimilar weldments joined by constant and pulsed current TIG welding techniques

ABSTRACT Higher heat input rates and uneven thermal cycles involved in fusion welding processes effect HAZ properties and causes to develop residual stress across fusion zones. These thermal stresses reduce the service life of welded structures. To understand the thermal cycles, In-Situ peak temperatures and their distribution over the weld surface of similar and dissimilar combinations of Monel 400 and AISI 316 base plates joined by constant and pulsed current TIG welding processes are measured with Infrared thermography technique at different time intervals. After welding the joints, thermal stresses developed across the joints were measured using X-ray diffraction technique. The stress measurements were made on weld surfaces of fusion zone and HAZ on either side of base metals. Higher temperature values were recorded during constant welding technique than the pulsed welding technique. Also, the heat affected area was more in weldments of constant welding technique. The maximum temperatures of 1657 0C, 1711 0C and 1748 0C were recorded in CCGTAW process during pass-1, pass-2 and pass-3 welding, respectively. Whereas, in PCGTAW process, maximum temperatures of 1434 0C, 1509 0C and 1634 0C were recorded during pass-1, pass-2 and pass-3 welding, respectively. The overall reduction in temperatures in PCGTAW process was 10.6%, which could affect the cooling cycles during solidification. Both the welding techniques have exhibited development of compressive natured residual stresses in dissimilar joints. The heat concentration at fusion area was reduced in pulsed technique that resulted in lower residual stresses.

Preliminary Research for Development of MW-TIG Hybrid Welding System

The paper aims to report preliminary researches towards to development of new hybrid welding system by coupling a microwave beam with a TIG torch. The main research was focused on the designing of hybrid system as well as to establish the heating/welding mechanism by coupling two different thermal sources. Therefore, a specific welding chamber was designed taking into consideration the limitations provided by microwave waveguide technical specs, geometrical shape and dimensions of the TIG torch as well as the temperature monitoring during welding process and video surveillance for data recording. A microwave generator with adjustable power from 0 to 1250 W was coupled with a TIG torch and welding power source in order to establish the main parameters for hybrid system. The preliminary researches reported that the MW-TIG hybrid welding could be applied to eutectic joining of materials using low power (up to 600 W) injected from microwave generator as well as low welding current (up to 20 A). The flow of shielding gas have been established initially to 2 l/m. The research related to stabilization of MW-WIG plasma arc have been studied by increasing the flow of shielding gas up to 10 l/m. The results have shown that the microwave generator and TIG torch can be coupled to obtain hybrid-welding process without any matching tuning devices but with risks for damaging the microwave generator. Further researches will be done in order to design auxiliary devices to optimize the hybrid-welding process and to avoid any unwanted plasma arc discharge from welded base materials to microwave generator. In terms of temperature monitoring, an infrared pyrometer has been used. The IR pyrometer was targeted to the base materials in order to be able to measure their temperature without any influences from plasma arc. The results obtained have shown a stable plasma at average microwave power around 400 W even without any TIG current.

Effect of angle, distance between electrodes and TIG current on the weld bead geometry in TIG-MIG/MAG welding process

Appropriate control of the weld pool is essential to obtain weld beads in accordance with project specifications. In this context, the TIG-MIG/MAG welding process has appeared as a viable alternative, mainly due to the greater independence between the deposited material and the heat transferred to the plate. Therefore, this study aims to evaluate the influence of input variables in TIG-MIG/MAG welding process on the weld bead geometry. Welds were made varying the TIG current, the TIG torch angle, the MIG/MAG torch angle, and the distance between the electrodes. It was found that it is possible to act upon the geometry of the weld bead varying the parameters evaluated. A larger fusion zone area and penetration are achieved by TIG current TIG torch angle and MIG/MAG torch angle in maximum and the distance between the electrodes in minimum values. Greater bead width is obtained by using the TIG current and MIG/MAG torch angle in the minimum value and distance between electrodes and the TIG torch angle in the maximum values. The highest reinforcement is obtained when using the TIG current, TIG torch angle, and MIG/MAG torch angle in maximum values and the distance between electrodes at the minimum value.

Observation of Arc Behaviour in TIG/MIG Hybrid Welding Process

In this project, the influence of TIG currents’s variation on arc stability of TIG/MIG hybrid welding was studied by comparing with MIG welding process. The welding current-voltage waveform was analyzed to characterize the arc stability of the MIG arc. From the observations, the introduction of TIG arc as low as 60 A of current significantly change the MIG arc stability in TIG/MIG hybrid welding. The length of MIG arc in TIG/MIG welding increased with the introduction of the TIG arc as compared with MIG welding. The increase of arc length was due to the arc interaction between the TIG arc and MIG arc, which is affecting the wire melting rate. At the maximum TIG current, the diameter of the molten droplet decreased with the increment of droplet transfer frequency.