Gas Metal Research Articles

Microstructural and Mechanical Properties of CAP-WAAM Single-Track Al5356 Specimens of Differing Scale

The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component’s structure and properties.

Power quality analysis of Gas Metal Arc Welding process operating under different drop transfer modes

. This work deals with power quality analyses related to the effect of different drop transfer modes in Gas Metal Arc Welding (GMAW) processes. The different drop transfer modes of GMAW process could be classified into: short-circuiting, globular, spray and pulsed. The correct choice of GMAW parameters is essential for optimal performance of the welding process. On the other hand, optimal parameters (from the point of view of the welding process) can lead to different power quality problems on the AC side of the local electric utility, according to the desirable transfer mode. In this sense, some power quality analysis based on metering results related to voltage fluctuations, harmonics and interharmonics will be presented to investigate the relationship between power quality problems and GMAW process operating under different drop transfer modes.

The evolutionary path of void galaxies in TNG300 simulation

ABSTRACT The properties of galaxies in low-density regions of the universe suggest an interplay between galaxy formation and environment. However, the specific reason why this particular large-scale environment influences the evolution of galaxies remains unclear. This paper examines the properties and evolutionary paths of galaxies within cosmic voids using the Illustris TNG300 simulation. The population of void galaxies at z = 0 has a higher star formation rate, a smaller stellar-to-halo-mass ratio, higher gas metallicity, and lower stellar metallicity in comparison with non-void galaxies at fixed stellar mass. Our analysis shows that these differences are mainly due to the characteristics of galaxies classified as satellites, for which the largest differences between void and non-void samples are found. Although the mean number of mergers is similar between void and non-void samples at a fixed stellar mass, void galaxies tend to experience mergers at later times, resulting in a more recent accumulation of accreted stellar mass. While the mean net accreted mass is comparable for high-mass galaxies, low-mass void galaxies tend to exhibit higher fractions of accreted stars than non-void galaxies. This finding challenges the common notion that void galaxies predominantly experience growth with infrequent mergers or interactions. With this paper, we also publicly release our void catalogue as part of the IllustrisTNG project.

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Process parameters and their effect on metal transfer in gas metal arc welding: a driving force perspective

AbstractIn gas metal arc welding (GMAW), the optimization of process parameters and the control of metal transfer is pivotal for achieving superior welding outcomes. This study meticulously examines the roles of core process parameters in metal transfer: wire extension and arc geometry, which includes arc length and inter-cathode distance. Using a unique MIG-based non-transferred arc system with symmetrically arranged tungsten cathodes we have achieved distinct control over wire feed rate and arc geometry, independent of the arc current. We investigate the interplay of these parameters and their consequential influence on the driving forces governing metal transfer. While increasing the wire extension enhanced inertial forces, it did not lead to consistent transitions in the metal transfer modes. In contrast, adjusting arc length and inter-cathode distance effectively controlled the electromagnetic force acting on molten droplets, as quantified by the arc spread angle $$\theta$$ θ . Notably, an increase in the arc spread angle resulted in the elongation of molten droplets. This study clarifies the fundamental relationships between driving forces and process parameters in GMAW. Additionally, it introduces a more advanced evaluation model for electromagnetic force and offers a comprehensive strategy for refining welding control techniques.

Microstructure and Mechanical Properties of High-Strength AA6011 Aluminum Alloy Welding with Novel 4xxx Filler Metals.

Welding high-strength 6xxx aluminum alloys using a commercial ER4043 filler often results in inferior joint strength. This study investigated the effects of newly developed Al-Si-Mg filler metals with varying Mg (0.6-1.4 wt.%) and Mn (0.25-0.5 wt.%) contents on the microstructure evolution and mechanical performance of high-strength AA6011-T6 plates using gas metal arc welding. Two commercial fillers, ER4043 and ER4943, were used as references for comparison. The results revealed that increasing the Mg and Mn contents in the novel fillers resulted in sufficiently high alloying elements in the fusion zone (FZ), leading to higher microhardness. Under as-welded conditions, the weakest region of the joint was the heat-affected zone (HAZ). The joint strength was almost independent of the filler type and was controlled by the HAZ strength, measuring a UTS of 230 and 241 MPa for ER4043 and the other joints, respectively. The higher Mg contents in the novel fillers promoted the precipitation of a large volume fraction of fine β″-MgSi in the FZ during post-weld heat treatment (PWHT), resulting in superior strength and higher welding efficiency relative to the reference fillers. The optimal Mg content of the novel fillers was 0.6 wt.%. Increasing the Mn content of the filler metal had an insignificant effect. The FMg0.6 filler with 0.6% Mg achieved the best combination of strength (UTS of 410 MPa) and elongation (6.7%) as well as the highest welding efficiency (94%) after PWHT, among all of the fillers studied. However, the newly developed fillers adversely affected the impact toughness of the joints.

Microstructural characteristics of different heat-affected zones in welded joints of UNS S32304 duplex stainless steel using the GMAW process: analysis of the pitting corrosion resistance

Abstract The influence of specific microstructural characteristics on the properties of single-pass welding joints was assessed by optical processed images, transmission electron microscopy, microhardness measurements and corrosion tests conducted in various regions of the heat-affected zone (HAZ) in a lean duplex stainless steel. The welded joints were obtained with heat inputs of 1.5 and 2.5 kJ/mm using a gas metal arc welding (GMAW) process with a shielding gas enriched in Ar. Three selected regions in the HAZ showed different ferrite grain sizes and austenite fractions. The place in the welded joint where the HAZ was narrowest, and therefore experiences the highest cooling rate, is most prone to the formation of cubic CrN metastable nitrides. Conversely, the place where the HAZ was wider promotes the precipitation of stable Cr2N nitrides with more coalesced intragranular austenite (IGA) particles, where presumably random interfaces predominate. The HAZ region where the cooling rate was the highest presented more pitting corrosion resistance.

Investigation of tensile and fatigue properties of an austenitic stainless steel part fabricated by WAAM

Austenitic stainless steels are used in many industrial applications and the use of components produced from this material by the wire arc additive manufacturing (WAAM) method has gained interest. Since damage of metallic parts generally occurs due to fatigue, it is necessary to understand their fatigue properties. This study focused on the determination of tensile and fatigue properties of an austenitic stainless steel structure produced by WAAM. For this purpose, a medium-sized part was fabricated using 308LSi metallic wire and gas metal arc welding (GMAW) technique. Hardness tests and microstructure examinations were also performed on the part. In the tensile tests, it was found that the strength and ductility of the vertical and horizontal samples were different. However, the fatigue test results of horizontal and vertical specimens were very similar. The average fatigue limit was found to be 195 MPa, and the fatigue life of the sample reached 107 without any macro damage. As a result of the hardness tests, the average hardness was calculated as 197 HV0.5. In the microstructure studies, different ferrite formations were observed in the austenite matrix on the bottom, middle and upper zones. The changes in microstructure were mostly attributed to the exposure of multiple layers to different heating and cooling rates during WAAM.

Analyzing microstructural, residual stress, and mechanical characteristics in dissimilar welds of Inconel 59 and AISI 904L through double-pulsed gas metal arc welding

In this research, dissimilar welding of the nickel-based superalloy Inconel 59 and austenitic stainless steel AISI 904L steel was successfully done with double-pulsed gas metal arc welding (DP-GMAW) using the filler ERNiCrMo-13. Macroscopic analysis showed a defect-free weld with an aspect ratio of 2.4, attributed to the efficient heat delivery (0.642 kJ/mm) in DP-GMAW. The microstructure of the weld joint was examined through both optical microscopy and scanning electron microscopy. Examination of the microstructure of the weld interface exposed grain coarsening near the heat-affected zone on the AISI 904L side. In contrast, the weld fusion zone contained fine equiaxed dendrites. Microsegregation and alloying element migration across the entire weld area were assessed through energy dispersive X-ray spectroscopy point analysis and line mapping, revealing controlled microsegregation across the region. X-ray diffraction (XRD) analysis was used to ascertain the average grain size (38.41 nm) and secondary phase composition. The XRD-cosα method was used to assess the residual stress of the weld joint, revealing tensile residual stress in the weld zone and compressive residual stress in other regions. Tensile, Charpy impact, and Vickers hardness tests were conducted in the study to evaluate the strength, toughness, and hardness of a dissimilar weld. The impact of two cryogenic treatments, namely shallow and deep, on tensile and toughness characteristics was investigated in this study. The cryogenic treatments significantly enhanced the mechanical properties of weld samples compared to their as-welded condition, leading to an 11.5% increase in tensile strength and a 10% improvement in toughness.

Enhanced mechanical properties in nickel-aluminium bronze alloy via wire arc additive manufacturing with follow-weld forced cooling

In pursuit of enhanced microstructural and mechanical properties, follow-weld forced cooling wire arc additive manufacturing (CWAAM) was employed for the fabrication of nickel aluminium bronze (NAB) components. The application of compressed gas metal arc welding (GMAW) system was implemented to mitigate the interference of cooling gas with the arc. A comprehensive examination of the microstructural and mechanical was conducted with and without the cooling source. Compared to WAAM sample, the grains size in CWAAM decreased by more than two times, attributed to higher melt pool subcooling. The 〈100〉 texture in CWAAM specimens showed a decrease due to the emergence of equiaxed grains and grain refinement, reducing the anisotropy of materials. Moreover, the dislocation density in CWAAM samples increased by 62.7%, owing to forced cooling that generated additional dislocations and suppressed recrystallization. Consequently, the average 0.2% yield strength (338.7 MPa) and ultimate tensile strength (687.3 MPa) of CWAAM specimens exhibited an approximate increase of 20% and 8.6%, respectively, in comparison to WAAM samples. This enhancement in yield strength is primarily ascribed to grain boundary strengthening and dislocation strengthening, instead of solid solution strengthening or precipitation strengthening.

Assessment of Fatigue Life of Gas Metal Arc and Friction Stir Welded AA 6061-T651 Aluminium Alloy Joints: A Comparative Investigation

Assessment of Fatigue Life of Gas Metal Arc and Friction Stir Welded AA 6061-T651 Aluminium Alloy Joints: A Comparative Investigation

Realized volatility spillovers between energy and metal markets: a time-varying connectedness approach

This paper analyzes the degree of dynamic connectedness between energy and metal commodity prices in the pre and post-COVID-19 era, using the time-varying parameter vector autoregressive connectedness approach of Antonakakis et al. (J Risk Financ Manag 13(4):84, 2020). The results suggest that market interconnectedness increased slightly following the outbreak of COVID-19, although this increase was lower and less persistent than that observed after the Global Financial Crisis of 2008. Furthermore, we find that crude oil was the main net transmitter of shocks before COVID-19 while heating oil, gold, and silver were the main net transmitters of shocks during the COVID-19 pandemic. In contrast, natural gas and palladium were the main net receivers of shocks during the entire sample period, making these two commodities attractive hedging and safe haven options for investors during the pandemic. Overall, our results suggest that hedging and diversification opportunities decrease during crises. Furthermore, they indicate that accurate forecasts of the volatility of several commodities, such as natural gas and different metals, can be obtained by exploiting the information content of crude oil. However, they also reveal that crude oil lost its leading position as a net shock transmitter during the COVID-19 pandemic.

A comprehensive study of ultrasonic-assisted gas metal arc welding of high-strength steel

The present study investigated longitudinal ultrasonic vibrations applied uniformly perpendicular to the weld line as an efficient approach in the ultrasonic-assisted gas metal arc welding (U-GMAW) of high-strength steel. The penetration depth, microstructure, microhardness, mechanical properties, and corrosion of welded joints produced from GMAW and U-GMAW were experimentally explored at different welding conditions to evaluate their performance. The experimental findings show that welded joints produced by U-GMAW have a maximum ultimate tensile strength (UTS) of 18.7 %, while showing 35.4 % elongation and 57.4 % toughness compared to the GMAW-welded joints at optimal conditions. The surface morphology analysis of the welded joints emphasizes that the dendritic microstructures generated by U-GMAW are finer than the dendritic microstructures generated by GMAW. Moreover, the microhardness of welded joints produced by U-GMAW method is higher than the GMAW-welded joints. The results of the polarization test also confirm that the corrosion rate of GMAW-welded and U-GMAW-welded joints are 360 and 1.60 µm/year, respectively with a power of 30 %. These results show that the corrosion rate of welded joints produced by GMAW is much higher than the one produced by U-GMAW.

Framework for a finite element method-based simulation approach to fatigue assessment of welded joints using the 4R method

The increased tensile strength capacity of high-strength steels (HSS) can be utilized fully in static loads, for fluctuating loads, however, more detailed analysis of design and manufacturing is needed. This study presents a framework for investigating utilization of the finite element method (FEM) in multiparametric 4R method-based fatigue evaluation. More specifically, the aim of the current study is to produce a concept for determining the parameters of the 4R method using FEM, thus providing a tool for evaluating fatigue strength related factors numerically. The study examines gas metal arc welded (GMAW) longitudinal gusset joints made of HSS S700MC Plus. The simulation is carried out as a sequentially coupled welding analysis that includes material condition changes in the HAZ and the fluctuating response as a restart analysis. Experimental measurement is performed for comparison with the results of the numerical model in the intermediate stages of the analysis process, and in the final stage as regards fatigue life. The experimental and simulated sub-results are consistent, and the estimated fatigue lives are in relatively good agreement with the experimental fatigue results. The numerical method thus provides a tool to predict fatigue related factors considered in 4R to evaluate fatigue life of welded joints.

Investigation of the Effect of Free Wire Length on Mechanical Values in Joining AW 6061 T6 Aluminum Alloys Used in Railway Vehicles with MIG Welding Method

Bu çalışmada demiryolu araçları sektöründe özellikle hızlı tren gövde ve şasilerinin imalatında kullanılan AW 6061 T6 serisi alüminyum alaşımları MIG (metal inert gaz) kaynak yöntemi ile birleştirilmiştir. Çalışma kapsamındaki tüm numunelere PA (kaynak torcunun iş parçasına olan açısı 900 konumda yapılan kaynak) pozisyonunda BW (alın birleştirme) uygulanmış ve birleştirme işlemlerinde 150x300x3 mm ebatlarında plakalar kullanılmıştır. Mukavemet değerlerinin kıyaslanabilmesi için kaynaklı numunelere çekme testi, çentik darbe testi, sertlik testi uygulanmış, birleştirme bölgeleri makrografi ve mikrografi muayene ile incelenmiştir.

Emission characteristics and removal of heavy metals in flue gas: a case study in waste incineration and coal-fired power plants.

Heavy metal pollutants such as Hg, As, Pb, Cr, and Cd emitted from coal and waste combustion have received widespread attention. In this study, we systematically investigated the emission characteristics of heavy metals in waste incineration and coal-fired flue gases, focused on testing the removal effect of self-made cold electrode electrostatic precipitator (CE-ESP) on heavy metals in flue gas, and made a comparative analysis with the existing air pollution control devices (APCDs). Test results from waste incineration power plant showed that each APCD showed a certain effect on the removal of heavy metals in condensable particulate matter (CPM), with an average removal efficiency of bag filter was 86%, but its effect on Hg removal was slightly worse. Under the coupled field with electrified cold electrode plate operation mode, the average removal efficiency of CE-ESP on heavy metals in CPM was as high as 93%, including 76% for Hg. The removal efficiency of heavy metals (especially Hg) in CPM increased with the increase of flue gas temperature difference between inlet and outlet of CE-ESP. Test results from this coal-fired power plant showed that heavy metals were enriched in fly ash to a higher degree than in slag, the synergistic control of heavy metals in submicron particulate matter by the dust remover was not obvious, and there was a significant correlation between each heavy metal emission factor and its content in coal. Under the temperature field with non-electric cold electrode plate operation mode, the overall effect of CE-ESP on the removal of gaseous heavy metals was better than that of particulate heavy metals. Under the conventional electric field operation mode, CE-ESP was less effective in removing particulate Cr and gaseous Hg0. Under the coupled field with electrified cold electrode plate operation mode, the average removal efficiencies of CE-ESP for particulate and gaseous heavy metals were 82.37% and 76.16%, respectively.

Stability Analysis of Metal Active-Gas Welding Short-Circuiting Transfer Based on Input Pulsating Energy.

In this study, a platform for a welding experiment, used to collect input and output electrical signals, was constructed, and the algorithm for the input pulsating energy interpolation line (IPEI) was given. Experiments with MAG surface straight line welding were conducted at various voltages. Analysis of the IPEI in relation to the welding current was performed while combining real-world welding occurrences with high-speed camera images of droplet transfer. It was established that the IPEI can be employed as a characteristic parameter to assess the stability of the short-circuiting transfer process in MAG welding. The three criteria for assessing the stability were the spectrum, approximation entropy, and coefficient of variation. A comparative analysis was conducted on each of these approaches. It was determined that the most effective technique is approximation entropy. The approximation entropy of the welding current and IPEI are also highly consistent, with a correlation coefficient as high as 0.9889.

Review of MIG and TIG welding current variation of low-carbon steel materials based on tensile strength

SS400 and ASTM A36 a low-carbon steel materials that are used in the industry in the connection process to create materials according to the design. The aim of this research is to review the mechanical properties that occur in low-carbon steel materials in the MIG and TIG welding process with current variations and provide advice on low-carbon steel in welding. The materials used are ASTM A 36 and SS 304 steel. MIG welding uses a plate with a thickness of 6mm and uses AWS A5.18 ER 705-6 electrode diameter of 1.2mm. TIG welding uses a cylinder with a diameter of 6mm. The method of this review reported the tensile strength of low-carbon steel ASTM A36 with current variations of 150, 155, and 160A for MIG. Current variations of SS304 low-carbon steel are 80, 100, and 120A for TIG. The result of tensile strength with the MIG process produces the highest average current of 150 A of 354.92MPa. The results of tensile strength TIG process for 100A of 1007.31 MPa. The suggestion of this review is in MIG welding a greater current is required to obtain a high tensile strength value than the current required for TIG welding on low-carbon steel ASTM A 36 with a carbon content of 0.29% C and on SS304 with a carbon content of 0.042% - 0.07% C. Welding for stainless steel material can be used on TIG welding to get maximum tensile strength values. For ASTM A36 steel materials, MIG welding can be an option.

Robotizing double-electrode GMAW process through learning from human welders

Gas metal arc welding (GMAW) is the most robotized arc welding process and most widely used process for wire arc additive manufacturing (WAAM). Double-electrode GMAW (DE-GMAW) is its novel modification achieved by adding a second/bypass electrode. It provides the capability to freely adjust the base metal current (heat input) without changing the wire current (mass input). However, it must be robotized in order to be adaptive to manufacturing variations and constraints. Due to the complexity of the process, we propose learning from human welders through their attempts to adjust the bypass electrode in collaboration with the robotized GMAW. To generalize human success using a follower robot/surrogate, the distance between the wire and bypass electrode is proposed as the process state to quantify human observation and operation. As such, Inertial Measurement Unit (IMU) sensors are integrated to track the wire and bypass electrode operated by both the lead robot and the human welder. To interpret human adjustments per arc observation, a Convolutional Neural Network (CNN) is employed to process arc images and calculate the distance. The automatically obtained distance labels from IMU signals are used to train the CNN; however, they are noisy and inaccurate. Thus, the CNN is finely tuned through transfer learning using manually labeled distances. With accurately automatically calculated distances from the finely tuned CNN for all the data, the demonstrations from human welders are analyzed. The generalized knowledge is implemented by a robotic surrogate, substituting for the human welder to fully automate the DE-GMAW. Experiments demonstrated the superior performance of the fully robotized, and adaptively controlled, DE-GMAW process.

Effect of interlayer temperature and cold wire addition in Wire Arc Additive Manufacturing on carbon steel

Wire Arc Additive Manufacturing (WAMM) consists in the manufacture of metallic preforms from the deposition of multilayer weld beads on a substrate, that is, from a three-dimensional model, the object is divided into layers defining the trajectories in which the addition of metal will be made, with the use of a robotic manipulator. The objective of this work is to study the influence of the addition of cold wire and the effect of interlayer temperature in the WAAM process, comparing it with the deposition made with a single wire, observing mechanical properties such as tensile strength, hardness, in addition to the cooling time for different interlayer temperatures and the geometry of the manufactured parts. A GMAW (Gas Metal Arc Welding) system was used coupled to a robotic manipulator, with multiple wires of 1.6 mm in diameter for the energized wire and 1.0 mm for the cold wire, both classified as ER70S-6. In order to manufacture the specimens for the tensile test, 20 layers were superimposed in a straight line, forming a wall, varying the interlayer temperature between each layer, using 100°C, 150°C and directly, with no waiting interval between layers. In general, a shorter cooling time was observed for the walls manufactured with the addition of cold wire when compared to depositions with a single wire. In addition, it was noted that the cold wire also influences the height and thickness of the pieces. In the mechanical tests, the cold wire did not significantly influence the hardness values. The highest values were found in the 100°C samples. For the tensile tests, it was observed that, in general, the addition of cold wire tended to increase the maximum tensile strength of the samples.