Gas Tungsten Arc Welding Welding Research Articles

Effect of Welding Current on Mechanical Properties and Microstructure of Aluminium AA1135 Alloys by Gas Tungsten Arc Welding (GTAW)

Aluminium alloys have a wide range of applications in the defence and aerospace industry, including for the manufacture of fuel tanks. The welding Current and type of filler metal significantly affect the microstructure formed and the mechanical strength of metal joints. This study aimed to determine the effect of the kind of filler metal (ER5356 filler metal) and welding current (140 amperes, 160 amperes, and 180 amperes) on the mechanical properties and microstructural of aluminium alloys AA1135 by the GTAW welding process. The results showed that the dendrite size increased with increasing welding current. Furthermore, the micro-hardness of the weld metal shows a decreasing trend with increasing welding current. The maximum tensile strength was obtained at a current power of 160 amperes, and all specimens failed at HAZ. The fracture surface of tensile test observations using SEM showed brittle fracture for Er5356 filler metal specimens, while on the fracture surface of the base metal tensile test specimens, it was observed to show ductile fracture. Welding with a current strength of 180 amperes has met the standard acceptance criteria because no cracks were found on the face bend or the root bend specimen

Subsequent welding of mild steel in the pipeline industry: mechanical, wear and microstructure characteristics

In this work, an attempt was made to join MS IS2062 using a combination of gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes using various welding parameters to get the best weldability. An initial scanning electron microscope study was conducted to determine the microstructure of the sample. In addition to measuring and correlating microstructures and welding parameters, mechanical properties like tensile strength and microhardness are also measured. Here, friction force (FF) and specific wear rate (SWR) were carried out to analyse the tribological behaviour of the weld joint. It was found that the weld MS IS2062 by subsequent welding achieved 15% and 5% higher yield strength and 5% and 4% harder than SMAW and GTAW. Pull-off and cracks were found in the tensile fracture image, and changes in grain boundaries have been observed in the microstructural study. The contact pressure shows the greatest influence on roughness and FF; at the same time, velocity influences the SWR, as found in the experimental results. The subsequent welding process was performed with good stabilisation by balancing between the SMAW and GTAW welding, and to obtain superior properties, we must optimise our results and choose the best possible method.

Influence Of External Magnetic Field On Mechanical And Metallurgical Properties Of Pressure Vessel Steel (Sa 516 Grade 70) Welds Using Gas Tungsten Arc Welding

Abstract The mechanical and metallurgical properties of weld play the most important role in the performance of welds which needs to be enhanced. The superimposing external magnetic field to the welding arc provided wonderful and favourable results for improving the shape and properties of weld. In this research, different configurations of specially designed electromagnets were used to investigate their effects on weld characteristics of SA 516 grade 70 welds. It is observed that 0-0-S-N configuration yielded maximum penetration (3.92 mm) compared with other configurations as well as the conventional gas tungsten arc welding (GTAW) process. Tensile test, Charpy impact test and microhardness were performed to investigate the mechanical properties and microstructure analysis was used to determine the metallurgical properties of the weld joints. The result shows that the tensile strength, impact strength, and microhardness of magnetically controlled GTAW (MCGTAW) weld was 620MPa, 275J and 198HV respectively which is 3.16%, 22.76%, and 1.51% higher than weld produced by GTAW process. It has also been observed that electromagnetic stirring refined the microstructure of the weld pool. The average grain size of MCGTAW weld was 31.035µm whereas 42.558µm average grain was obtained in conventional GTAW weld. The electromagnetic stirring enhanced the weld cooling rate resulting formation of more acicular ferrite which is desirable.

Mechanical Properties Of Welding API 5l X-65 Cladded UNS N08825 Material Due To The Effect of Welding Repair

Abstract This study evaluate the mechanical characteristics and microstructure of API 5L X-65-clad UNS N08825 during repair welding. Gas tungsten arc welding (GTAW) and shielded metal arc welding were used in combination to carry out the welding and the repair welding (SMAW). Filler metals ER NiCrMo3 and E NiCrMo3 were used throughout the GTAW and SMAW welding processes. The first specimen served as the primary focus, after which the weld areas of the remaining four specimens were ground, re-beveled, and then re-welded using the same parameters. It performed tensile testing, bending tests, Impact Charpy tests, macro photography tests, and Vickers hardness tests. Repairs weld carried out, the heat-affected zone's hardness in the capping region increased. The findings of the tensile test demonstrate that the tensile strength is not considerably impacted by the welding repair at any particular welding repair location. The biggest decline in the number is caused by the welding repair at PTR 2, which is 0.83 percent. The heat affected area (FL) value decreased by 10.44 percent according to the charpy impact test results. The PTR 1 and PTR 2 areas in the weld metal area had the lowest charpy impact test results, respectively, of 88 J and 258 J.

General expressions for heat distribution, pressure, and current density in argon welding arcs

In welding and wire-arc additive manufacturing (WAAM), a mobile arc is the heat source that enables the deposition of metals and the resulting properties of the final product. Because the arc involves temperatures of 20 000 K, and gas velocities of the order of 300 m/s, there are only a few experiments and models available to determine optimal, or at least acceptable, parameters for the operation such as current, voltage, and arc length. On the other hand, there is a lack of engineering guidance to optimize the processes resulting in costly and time-consuming trial-and-error optimization methods, which also involve wasteful use of energy and scrap parts. In this work, a numerical model of the gas-tungsten arc welding (GTAW) arc was created and validated against experiments. The model considers the arc interactions between a non-consumable electrode and the weld pool and accounts for multiple coupled heat transfer mechanisms: Joule heating, conduction, advection, radiation, and Thomson effect. The conditions considered cover the vast majority of GTAW welding operations. The results are generalized in the form of engineering expressions suitable to be embedded in metamodels, in which the heat source is just a part. Applications include penetration and width of welds and deposition rate in external-wire WAAM.

The Strength Material Welding Dissimilar of Method GTAW AISI 1045 With HSS for Application Milling Tool

Dissimilar welding is a permanent joining of two dissimilar materials as the application of this welding is used in milling tools that receive a large load when used. It is certain that there is a change in the microstructure between the HAZ (Heat Affective Zone) regions, and causes a decrease in the strength of the material, because residual stresses, defects, and cracks due to dissimilar welding will become a problem in itself. This study will connect two different materials between AISI 1045 and HSS (High Speed Steel), using the GTAW (Gas Tungsten Arc Welding) welding method. Welding results from tensile strength, hardness and microstructure inspection as well as calculating grain size in the weld metal, HAZ and base metal areas are the focus of the analysis.
 This dissimilar welding will compare three welding amperes that is, ±110A, ±167A and ±225A. This amperage is used based on the welding results that have been carried out for both materials with the AWS standard for circular welding of solid round materials such as the shape of a milling tool. GTAW welding method is very good and strong, but the hardness of the weld metal is large and will cause brittleness. The difference in hardness between weld metal and HAZ is significant due to the rapid heat input resulting in failure in the area between weld metal and HAZ.
 Tensile test results for amperage ±110A tensile strength 84.70 kgf/mm2, the hardness is 665.58 HV in the HAZ area of HSS material. Examination of the microstructure in this area has austenite, martensite and carbide phases, it looks less than ±167A of amperage welding, the results of the hardness test are 774.70 HV in the HAZ area of HSS material so that this area will be more brittle. The smaller the grain size, the higher the hardness. Selection of dissimilar welding filler metal produces good joint strength. While the amperage welding of ±225A broke on welded metal with a tensile strength of 43.41 kgf/mm2, the hardness in the HAZ area was made of HSS with a hardness of 772.37 HV. The smallest hardness value is in the base metal area of AISI 1045 material with a hardness of 264.45 HV. The difference in hardness is much different between HSS and AISI 1045, indicating the use of filler metal with poor connection strength for large amperes.

Evaluation and Prediction of Formation of Heat-Affected Zone and Mechanical Properties According to Welding Method of STS 316L/A516-70N Clad Plates

Two welding methods of FCAW (Flux-cored arc welding) + FCAW, and FCAW + GTAW (Gas tungsten arc welding) were compared to identify effective routes for STS 316L/A516-70N clad stainless steel. Since the welding speed of the FCAW + GTAW welding method is slower than that of the FCAW + FCAW welding method, the amount of heat input is large, the size of the heat-affected zone formed is larger, and the amount of angular deformation is also large. The microstructure and deformation of the welding specimens were investigated by computational simulation, and the results were compared with calculated results for actual specimens. The results were very similar, thus confirming the high accuracy of the calculation. After measuring the hardness value of the actual welded specimens, the specimen welded by the FCAW + FCAW welding method was found to have a higher hardness value. The hardness of the welded portion of the FCAW + GTAW specimen tests tended to remain at nearly the same value throughout the specimen, indicating that the FCAW + GTAW hardness profile is desirable. In the computer simulation, butt welding was used to set the optimal heat source conditions for the two welding methods, and the effect of heat formed during welding was confirmed using the thermal analysis results according to the conditions. Based on the butt welding conditions, the residual stress and strain for the two welding methods are discussed, using calculations for the welding of C-seam (circumferential seam) and L-seam (longitudinal seam) used in the manufacture of pressure vessels.

Mechanical and Microstructural Characterization of Inconel 625 Welds After Corrosion at Supercritical Water Conditions

Abstract Inconel 625 is considered one of the candidate materials for fuel cladding in the Canadian supercritical water reactor. Gas tungsten arc welding (GTAW) is being evaluated as a joining technique for SCWR fuel cladding since this method is widely used to join components in the power and nuclear industry. The thermal cycle, during the GTAW process, produces different types of microstructures that affect the material's mechanical properties. The objective of this work was to study the effect of corrosion testing at supercritical water conditions on mechanical properties of Inconel 625 base material (BM) and weldments. Tubular Inconel 625 specimens were welded using a GTAW orbital process. Corrosion testing was conducted in an autoclave at 575 °C (848.15 K) and 23.5 MPa for 500 h (1.8 × 106 s). Weld characterization included mechanical tests, optical microscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The composition of second phase precipitates observed during microstructural characterization was elucidated using equilibrium phase diagrams. Tensile tests showed that both BM and welds displayed an increase in strength and a decrease in ductility after corrosion testing. The ultimate tensile strength increased about 2% and 9% for the BM and the weldment, respectively. The maximum specimen elongation decreased around 35% for the BM and 45% for the weldment. The microstructure showed indications of second phase precipitation and grain morphology changes produced by both welding and corrosion processes. Results show that ductility of Inconel 625 GTAW welds is significantly reduced after exposure to supercritical water for 500 h (1.8 × 106 s).

The Effect of GTAW Welding Current on the Strength of AISI Steel 1045

Welding is a process of joining materials by melting metal at high temperatures. Gas Tungsten Arc Welding (GTAW) is one of welding method to join metals. This welding process will affect the mechanical properties of a material. So, it is necessary to conduct a study on changes in mechanical properties that occur. This study aims to determine the mechanical properties of AISI 1045 medium carbon steel using the GTAW welding process with a current variation of 80 A and 100 A. The welding was used the AWS EWTh-1 tungsten electrode and ER70S-G filler wire. The type of connection was used a butt weld joint and a single V groove seam with an angle of 60o. The standard of ASTM E8 was used for the manufacture of tensile test specimens. The results of tensile testing with welding current of 80 A was obtained an average stress of 518.463021 N/mm2 and the strain of 19.55%. For welding with a current of 100 A, the average stress was 548.814727 N/mm2 and the strain of 26.44%. Based on the fracture that occurred in the specimen, the critical area for fracture was the Heat Affecting Zone (HAZ), which the area has undergone a phase change during the cooling process. The weld area of connection part in the welding process has higher strength than the HAZ area.

Comparative studies on weldability and mechanical characteristics of semi- killed steel using different arc welding technique

The main objective of this study is to examine the weldability and mechanical properties of semi-killed steel of E250BR grade which is mostly used in gear box casing. Three different arc welding methods i) GMAW (Gas Metal Arc Welding) ii) GTAW (Gas Tungsten Arc Welding), and iii) A-GTAW (Activated Gas Tungsten Arc Welding) were employed in this study, and the respective weld joints mechanical properties were evaluated and compared with each other. Visual inspection of the specimens shows that the GTAW and A-GTAW processes offer excellent weld bead geometry. Visual and radiographic inspections showed no crack or discontinuity is in the weld joints. The weldment produced by A-TIG welding has the highest aspect ratio, which is due to the reverse Marangoni convection effect. The tensile and hardness test outcomes exhibited that the mechanical properties of the parent metal were not affected by the welding processes, but impact test results showed a lack of energy absorption by the specimen from the A-GTAW process. A-GTAW welding had the highest Ultimate Tensile strength, which was 2.5 percent to 5 percent higher than the other processes employed in this study. Weldments fabricated using GTAW welding have the highest impact toughness, which is 43.5 percent and 51.85 percent more than the other two processes. Vickers hardness test reveals that joints made with the GTAW process are better than the other counter parts.

Weldability Evaluation of GMAW and GTAW for Al-6.7 wt.% Mg Alloy

In this study, the arc weldability of an aluminum alloy was investigated based on its Mg content. The base materials used in the experiments were aluminum with a Mg content of 6.7 wt.% (referred as Al-6Mg) and commercial Al5083-O. The weldability of two types of fusion welding methods was evaluated: gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW). The tensile strength, hardness, alloy composition, and microstructure properties of the welds of two types of the aluminum alloys were compared. The tensile strength values of the GMAW and GTAW welds of Al-6Mg were 20% and 10% higher than those of Al5083-O, respectively. The weld hardness of the GMAW and GTAW welds of both aluminum alloys were similar. Al-6Mg by GMAW and GTAW were smaller than those of Al5083-O. Based on the results of analysis of the welds, the residual magnesium content was as high as 37% by GMAW and 30% by GTAW.

Appreciable-tuned ferrite/austenite phase balance in the fusion zone of GTAW welds via an assisted magnetic field

In the present paper, a transverse magnetic field was applied to gas tungsten arc welding (GTAW) for 2205 DSS in order to regulate the weld microstructure, which has not been investigated so far. The results indicated that the application of magnetic field not only can increase the austenite/ferrite phase ratio of the welds, but also refine the ferrite grains, and a magnetic field with a frequency of 1 Hz worked best. Both of the above can be attributed to the slower cooling rate of the welding pool with arc oscillation. Hardness test showed that the arc oscillation exerted a significant influence on hardness distribution. Under the effect of a low frequency (1 Hz) magnetic field, the hardness level of the weld metal was close to that of the base material. However, when no magnetic field was applied, the hardness level of the weld increased.

Remanufacturing the AA5052 GTAW Welds Using Friction Stir Processing

Progress in sustainable manufacturing is a crucial element to minimise negative environmental impacts. The conventional fusion weld process used to join aluminium alloys resulted in coarse grain structure, inevitable defects, and severe joint softening. Friction stir processing (FSP) has the potential to modify the microstructure of materials in joint structure and improve the mechanical properties. In this investigation, the effect of friction stir post–processing was evaluated to study the microstructural characteristics and mechanical properties of GTAW (gas tungsten arc welding) welds in the aluminium 5052 alloy. During FSP, the grains’ dendritic microstructure was destroyed, and the dynamic recrystallisation resulted in a very fine and equiaxed grains structure in the fusion zone. The hardness of the friction-stir-processed welds significantly improved because of microstructure grain refinement. The processed joint demonstrated higher ultimate tensile and yield strength (~275 MPa and 221 MPa, respectively) and superior elongation (31.1%) compared to the unprocessed weld; at the same time, the mechanical strength (yield and ultimate tensile) is similar to that of the base metal.

Study on weldability and effect of post heat treatment on mechanical and metallurgical properties of dissimilar AA 2025, AA 5083 and AA7075 GTAW weld joints

Gas Tungsten Arc Welding (GTAW) has been extensively in use over a period in mechanical industry. Most of the problems associated with the structural development involving Aluminium is still a challenging and requires a methodological study to understand weldability of dissimilar Aluminium base materials. In this present study, mechanical and metallurgical properties of AA 2025, AA 5083 and AA 7075 weld joints made with GTAW have been presented. Mean pulse current of 80 A to 100 A was selected to join the similar and dissimilar base material combinations to make comparative studies. Difficult to weld base material combinations, AA 2027 with other selected base materials, and with non-heat treatable base materials were subjected to post weld heat treatment. Tensile and hardness tests were performed to evaluate the properties of as weld and post heated dissimilar weld joints.

Realistic Model to Predict the Macrostructure of GTAW Welds for the Simulation of Ultrasonic Non destructive Testing

The knowledge of grain growth directions makes it possible to describe the material anisotropy, which helps to ensure the ultrasonic testing of welded assemblies and the assessment of their mechanical integrity. Here, we study multipass welds made of 316 L stainless steel manufactured by a Gas Tungsten Arc Welding (GTAW) process. We have developed a specific model to predict the grain growth directions using a phenomenological solidification model relevant for GTAW welds. This new model follows the philosophy of the MINA model, developed since 2000 and which predicts the grain growth directions for Shielded Metal Arc Welding (SMAW) multipass welds, taking into account information from the welding notebook and macrograph analysis. Unlike the MINA model, the new model does not require measurement of the remelting parameters on macrographs, which can be complex to perform. These parameters are calculated from the measurement of dimensions on associated beads on plate. In this paper, the development of this new model is presented and the results are shown.

Chemical pollutants in the respiratory zone of welders: Determination of concentrations and hazard analysis.

Welding pollutants have potentially dangerous effects on the health of welders. Analysis of exposure risks is an appropriate method for industrial hygiene occupational exposure. The present study aimed to determine the concentrations of exposure and risk evaluation of welders to fumes and gases in three common types of welding including Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW) and Gas Tungsten Arc Welding (GTAW). This cross-sectional study was carried out at a steel company. Samples were taken from manganese, chromium and nickel fumes with NIOSH 7300 method and for NO, NO2, CO and O3 gases using direct reading instruments. SQRCA method was used to assess the level of exposure risk. Our study showed that the highest and lowest concentrations of exposure to gases were observed in MIG and GTAW welding, respectively. Also, the highest and lowest concentrations of exposure to metals were observed in SMAW and GTAW processes, respectively. Mean exposure to M, Cr and Ni metals was 2.302, 3.195, and 1.241 mg/m3, respectively. Also, mean exposure to CO, NO, NO2 and O3 was 43.05, 27.88, 4.30, and 0.41 ppm, respectively. Results of risk analysis showed that O3, NO2 and Cr had high and very high risk levels in all welding processes. MIG and SMAW welders have a high occupational exposure to metal and toxic gases in welding. Preventive measures such as assessment of workplace air, installation of the ventilation systems, and providing appropriate respiratory protection devices for welders should be taken.

Effect of welding processes and heat input on corrosion behaviour of Ferritic stainless steel 409M

In the present work, Ferritic stainless steel 409M is welded with shielded metal arc welding (SMAW), gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) of welding current 90A, 100A and 110A. Four mm thick plates were used as base material and single V-joint was prepared for welding. Single pass welding was carried out. Microstructures in the transverse section were observed for base metal, Heat Affected Zone (HAZ) and weld joint. Corrosion rate of welded joints have been evaluated by weight loss method in sodium chloride (NaCl) solution. In this investigation results reveal that, corrosion rate of welded joint is more than the base metal. It is also found that corrosion rate increases on increasing welding current. It is observed that corrosion rate is more in SMAW than GMAW and GTAW weld joint. Results are discussed in the light of microstructure. Increased corrosion rate is attributed to welded structure and formation of HAZ due to variable welding heat input.

Argon localizing by concentration method for GTAW welding process of high chromium alloy steel pipes

The present invention relates to a novel argon purging device in butt joint welding for high chromium alloy steel pipes or more predominantly relates to a device which can be used for focusing of argon at root area of welding and also an approach for purging out the atmospheric air through the inert gas argon at butt welding of high thickness pipes of high pressure steam generators. The butt joint root welding of high chromium alloy steel pipes carried out by manual Gas Tungsten Arc Welding (GTAW) requires shielding from atmospheric oxygen. Otherwise, Chromium reacts with oxygen and forms Chromium Oxide (CrO2) which is termed as oxidation. In the conventional method of purging, the argon gas is fed into both ends of the pipe using two argon cylinders. The ends are closed with metallic end covers which have many inherent limitations like ineffective purging at the butt joint, more wastage of the inert gas argon, incomplete fusion, lack of penetration, root oxidation and formation of weak brittle structures etc. Present invention is to provide a device for argon supply in butt welding of high chromium alloy steel pipe which ensure substantially better shielding and thereby avoiding the root oxidation. The developed argon purging device has resulted in elimination of root oxidation in high chrome high alloy steel pipe butt joint welding, improved weld quality as well as reduced process time. Argon gas savings up to 87.5%, as only one fourth of an argon cylinder is used in place of 2 argon cylinders for purging one butt joint and the overall cycle time is reduced by 40%.

Microstructure and Mechanical Properties of AA7005 Alloy Joint by Fusion and Solid-State Welding Processes

In the present work, effect of gas tungsten arc welding (GTAW), gas metal arc welding (GMAZ) and friction stir welding (FSW) processes on microstructure and mechanical properties of AA7005 alloy were investigated. In general, conventional welding process like GTAW and GMAW is preferred by industries but they produce a joint efficiency of 55%. In this study, welding of AA7005 alloy was carried out with ER 5183 filler wire using GTAW and GMAW welding and without filler using solid-state FSW. Coarse grain with wide HAZ was observed in conventional welding which resulted in a reduction in tensile strength by 37 to 43%. Nevertheless, only a 17% reduction in strength was observed in FSW weld due to fine equiaxed grain size and precipitates in the weld. A joint efficiency of 83% was achieved by the FSW process.

Assessment of Impact Strength of Welds Produced by Cold Wire and Hot Wire Gas Tungsten Arc Welding (GTAW) Processes

Modified 9Cr 1Mo material is used as principal material of construction of Steam Generators (SG) for 500MWe Prototype Fast Breeder Nuclear Reactor (PFBR), at Kalpakkam, India. One of the major problems associated with welding of modified 9Cr 1Mo steel is poor impact strength of weld metal produced from the processes that involves the use of flux. Due to this reason, 100% Gas Tungsten Arc Welding (GTAW) process is chosen for fabrication of PFBR Steam Generators.The major limitation of conventional cold wire GTAW process is low deposition rate which makes it highly uneconomical especially for welding component with large section thickness. Therefore, hot wire GTAW process is selected for welding of PFBR Steam Generators wherever possible in addition to the conventional cold wire GTAW process. The impact properties of modified 9Cr 1Mo welds produced by hot wire GTAW process are compared with impact properties of cold wire GTAW welds. The impact strength of welds produced by hot wire GTAW process is found to be inferior compared to that of welds produced by cold wire GTAW process. Nevertheless, hot wire GTAW system has the benefit of high weld deposition rate with excellent profile of weld with reduced dilution and porosities