Gas Metal Arc Welding Process Research Articles

Comparison of fatigue crack growth design curves on GMAW and EBW joints of high strength steels

AbstractThere is a growing demand in the industrial sector for the use of high-strength structural steels (HSSSs), which can achieve a significant weight reduction in structures. These structural steels are usually produced by quenching and tempering (Q + T) or thermomechanical treatment (TM), and their applications in welded structures pose several challenges for the users. In industrial practice, gas metal arc welding (GMAW) is basically the most commonly used fusion welding process, which has a relatively high heat input. However, at HSSSs, there is a need for low heat input but, at the same time, productive welding processes. High-energy density welding processes, e.g., electron beam welding (EBW), offer a unique opportunity to weld these steels. The widespread use of HSSSs is also hampered by the fact that the benefits of high strength can be exploited primarily under static loading. At the same time, different welded structures made of HSSSs are often subjected to cyclic loading, and possible weld defects and material discontinuities are major risks in this case. During our experiments, GMAW and autogenous EBW processes were applied to make welded joints from S960 Q + T and TM structural steels. The fatigue resistance of the welded joints was characterized by fatigue crack growth (FCG) tests, considering the increased crack sensitivity of HSSSs. A statistical approach was followed both in the design of the experiments and in the evaluation of their results. Based on the test results fatigue crack propagation design curves were determined for the investigated GMAW and EBW welded joints. The design curves were compared with each other, with design curves of lower strength material (S690QL) and with the recommended fatigue crack growth laws of BS 7910.

Microstructural characteristics and properties of wire arc additive manufactured 304L austenitic stainless steel cylindrical components by different arc welding processes

Wire arc additive manufacturing (WAAM) is an advanced additive manufacturing (AM) technology that offers low cost and high deposition rates, making it suitable for building large metal parts for structural engineering applications. However, various welding procedures result in differing heat inputs and repetitive heating treatments throughout the deposition process, which can affect the microstructural and mechanical characteristics of the parts. In the current study, cylindrical parts made of 304L austenitic stainless steel (ASS) were manufactured using the WAAM technique, employing both gas metal arc welding (GMAW) and cold metal transfer (CMT) processes. This study explores the correlation between WAAM techniques and their effects on the bead geometry, microstructure and mechanical properties. The microstructure of the cylinders consisted of vertically growing austenite dendrites with residual ferrite (δ) within the austenite (γ) matrix. Compared to the bottom region (region ①), the top region (region ②) contained more residual ferrite. Although the microstructural characteristics from region ① to region ② are similar, they exhibit different ferrite morphologies. The rapid cooling rate in the CMT-AM process resulted in finer structures and a greater presence of ferrite phases in both regions compared to the GMAW-AM method. Cylinders produced by the CMT process displayed nearly uniform properties across both regions and demonstrated superior tensile properties, hardness, and impact toughness relative to those made using the GMAW technique. The WAAM 304L ASS cylinders also showed enhanced performance compared to stainless steel manufactured using traditional industrial forging standards, indicating that WAAM-processed 304L ASS cylinders are suitable for industrial applications.

Effect of welding speed variation on bead geometry of IN-625 weld bead on a medium carbon steel plate using synergic GMAW process

Gas Metal Arc Welding (GMAW) is widely applicable across various sectors due to its ease of operation, higher welding speed and high production rate. The present work aims to determine the effect of welding speed in a synergic GMAW process with ER-NiCrMo-3 wire to produce a bead-on-plate on AISI 4140 base material. The results showed that the beads produced were free from defects like porosity and cracks. The increase in welding speed decreases heat input (HI), bead penetration and weld width. However, the effect of speed was found least in heat input and most in bead penetration. The variation in bead geometry hence, clearly suggests that welding speed plays a significant role in the selection of weld parameters during the fabrication of IN-625 joints.

Study of microstructure and mechanical properties of SA553/SA537 steels joints using multi-pass welding for pressure vessels application

In this study, gas metal arc welding (GMAW or MIG) process was investigated for similar and dissimilar joints of SA553 and SA537 steel plates in different thicknesses with E NiCrMo-3 filler metal and 0–3 panel joint design that joined pressure vessels body to manholes. In order to examine the metallurgical behavior of the weld, optical and scanning electron microscopies were used. The effect of cooling rate (∂T∂t) on microstructure, strength and impact energy (cryogenic fracture toughness) were examined. By doubling the thickness (6–12 mm), the heat transfer rate or cooling rate (∂T/∂t) increased 4 times. Therefore, the strength and impact energy for the similar welding joint SA553 increased by about 8 % and for the similar welding joint SA537 by about 5 %. For dissimilar weld joints with different thicknesses, strength and impact energy are caused by the type of base metals and the different cooling rates of each base metal. Due to the high elongation of the E NiCrMo-3 electrode (30 %), there was continuous plastic deformation during bending tests. Also, by carrying out radiographic tests, the absence of cracks in welding structures was confirmed.

Experimental Investigation on Microstructure and Mechanical Properties of 15CDV6 High Strength Low Alloy Steel Welded Using Spin Arc Gas Metal Arc Welding Process

Experimental Investigation on Microstructure and Mechanical Properties of 15CDV6 High Strength Low Alloy Steel Welded Using Spin Arc Gas Metal Arc Welding Process

Controlling the high weld rejection rate of mechanized gas metal arc welding process (GMAW)

Controlling the high weld rejection rate of mechanized gas metal arc welding process (GMAW)

Investigation of the tensile strength of the CMT and PCMT joints of AA8011 aluminum alloy

The advanced variant of gas metal arc welding (GMAW) known as cold metal transfer (CMT) developed by Fronius in Austria is used to overcome heat-input- and fusion-related issues such as porosity and cracking in welding of AA8011-H18 alloy sheets. AA8011-H18 alloy sheets 3 mm thick were welded using normal CMT-GMAW and pulsed CMT (PCMT)-GMAW processes. The microstructure of the weld metal and heat-affected zone was analyzed using an optical microscope. The tensile properties and hardness of joints were evaluated and compared. The results revealed that the PCMT-GMAW joints showed 26.45, 48.97 and 40.42% improvements in tensile strength, yield strength and elongation, respectively, compared with CMT-GMAW joints. The superior tensile performance of PCMT-GMAW joints compared with that of CMT-GMAW joints is due to the current pulsing effects along with the wire retraction mechanism, which aids in reducing the heat input and controlled droplet transfer.

The effect of heat input on tensile strength, Vickers hardness, and microstructure on DMW of AISI 1015 and 304L SS through the GMAW process

This experiment was to evaluate the effect of heat input on tensile strength, Vickers hardness, and microstructural observations.The materials welded are AISI 1015 and 304L SS, and the joining process is Gas Metal Arc Welding (GMAW). The filler electrode used is ER70S-6 with a diameter of 1.2 mm, and the workpiece size is 300 x 125 x 3 mm with a butt-joint connection. The variations in welding current applied are 120, 130, and 140 A. Meanwhile, the voltage and welding speed in the experiment were kept constant.The maximum tensile test index was 380.08 MPa, and the Vickers hardness index was 376.85 HV, with the maximum heat input being 0.5943 kJ/mm. The macro- and microstructure, as well as structural inspection of the welded joints, were observed in the experiment. The best heat input effect for the DMW technique between 304L SS and AISI 1015 is 0.5943 kJ/mm at a plate thickness of 3 mm.Dissimilar Metal Welding (DMW) is widely applied in the power generation industry. Materials generally joined using the DMW technique are austenitic stainless steel (304L SS) and low carbon steel (AISI 1015).Using the proposed heat input approach is important for the dissimilar welding industry application to obtain the right product for its expected use.This paper presents the differences in heat input to reveal the weld properties by dissimilar welding processes, where the properties will be adapted for a particular use. Particularly in the application of dissimilar joints between 304L SS and AISI 1015 with a thickness of 3 mm, which requires an average tensile strength of around 380.08 MPa and an average yield strength of about 320.16 MPa, the heat input parameter can be recommended as 0.5943 kJ/mm.

Investigating arc and molten metal transport phenomena in gas metal arc welding with Ar–CO2 gas mixtures using a numerical method

This paper presents a numerical investigation of the transient transport phenomena of the arc and molten metal during gas metal arc welding (GMAW) using shielding gas mixtures ranging from 100% Ar + 0% CO2 to 80% Ar + 20% CO2. The thermophysical parameters of the Ar–CO2 mixtures, considering the presence of metal vapor, were calculated as a function for a temperature range of 1000–30 000 K. The influence of metal vapor content and CO2 proportion on the thermophysical properties of the mixed gas was discussed in detail. As the CO2 content increased from 0 to 20%, the shape of the arc changed from a bell to a cone due to the increase in mass density, specific heat, and thermal conductivity. The maximum arc temperature and velocity decreased with increasing CO2 content, resulting in larger droplets and a lower droplet transfer frequency. Although the change in electrical conductivity did not affect the arc shape, it did influence the arc temperature by altering the distribution of current density. Experiments of droplet transfer and arc behavior were carried out, and the results showed that the simulated droplet size, transfer frequency, and arc temperature distribution agreed well with the experimental values. These findings could serve as a theoretical tool for better understanding the underlying physical mechanisms of the GMAW process using different shielding gases, ultimately aiming to achieve high weld quality.

Comparative study about the results of HAZ physical simulations on different high-strength steel grades

AbstractWith continuous improvements, structural steels are available in even higher strength grades above 1000 MPa yield strength. As the great majority of these steels are used in welded structures, their weldability needs to be taken into account. Several factors can cause difficulties during welding of these steels, but in this paper the softening behavior and the toughness characteristics of the heat-affected zone (HAZ) are examined. As the critical parts of the HAZ in a real welded joint are relatively small, their investigating ability is limited. However, the physical simulation provides a way of evaluating specimens made from a given material to produce the specified HAZ areas in a suitable size range for subsequent testing. In this research work, three different strength categories of high-strength structural steels (with yield strength of 960 MPa, 1100 MPa, and 1300 MPa) are investigated by physical simulation. In the case of different technological variants of gas metal arc welding (GMAW) process, the effect of the cooling time t8/5 is investigated in different HAZ subzones considered to be critical. The thermal cycles were determined according to the Rykalin 3D model. The investigated cooling times were t8/5 = 5 s, 15 s, and 30 s. The properties of the selected coarse-grained, intercritical and intercritically reheated coarse-grained zones are analyzed by laser scanning microscope, scanning electron microscope, hardness test, and instrumented Charpy V-notch impact toughness test. Furthermore, additional investigation like JMatPro calculations, electron backscatter diffraction measurements, and prior austenite grain size calculation were carried out. As a result of the tests, the investigated heat-affected subzones indicated higher sensitivity to the welding heat input compared to conventional structural steels. Overall, the results of the tests show that the application of shorter t8/5 cooling time can be beneficial for the investigated high-strength steel grades, since significant toughness reduction and the risk of softening occur in the whole cooling time range.

Role of material properties on metal transfer dynamics in gas metal arc welding

In the gas metal arc welding (GMAW) process, metal transfer dynamics, influenced by wire material properties such as electrical conductivity and surface tension, serve as key sources of mass and heat for metal deposition on substrates. To elucidate the role of these material properties on metal transfer dynamics from a driving force perspective, this study examined molten droplet elongation across five distinct wires: Al, Cu, Fe, Ni, and Ti. Additionally, a unique non-transferred arc welding setup equipped with a consumable wire anode and two tungsten cathodes was introduced, allowing for observations at minimized arc lengths and preventing current concentration in molten droplets. For Al and Cu wires, while only projected-spray transfer was observed under sufficient arc length conditions, a shift to minimized arc length resulted in significant droplet elongation and a transition to streaming-spray transfer. This contrast emphasized the impact of high electrical conductivity in reducing the internal gradient of electromagnetic pressure and inhibiting the occurrence of streaming-spray transfer. Further substantiating this mechanism, Fe, Ni, and Ti wires revealed that higher electrical conductivity corresponded to an increased transition current to streaming-spray transfer. Additionally, surface tension played a crucial role in the formation of molten droplets and ensured transfer stability, with its influence varying at different current levels. These insights contribute to our comprehensive understanding of arc plasma and molten metal interactions. Our study proposes material-specific strategies to optimize metal transfer dynamics, leading to enhanced control over weld bead formation and overall mechanical properties of welded joints in the GMAW.

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.

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.

Evaluation of Austenitic Stainless Steel ER308 Coating on H13 Tool Steel by Robotic GMAW Process

Within the drilling, petrochemical, construction, and related industries, coatings are used to recover components that failed during service or to prevent potential failures. Due to high stresses, such as wear and corrosion, which the materials are subjected to, industries require the application of coating between dissimilar materials, such as carbon steels and stainless steels, through arc welding processes. In this work, an austenitic stainless steel (ER308) coating was applied to an H13 tool steel substrate using the gas metal arc welding (GMAW) robotic process. The heat input during the process was calculated to establish a relationship between the geometry obtained in the coating and its dilution percentage. Furthermore, the evolution of the microstructure of the coating, interface, and substrate was evaluated using XRD and SEM techniques. Notably, the presence of martensite at the interface was observed. The mechanical behavior of the welded assembly was analyzed through Vickers microhardness, and a pin-on-disk wear test was employed to assess its wear resistance. It was found that the dilution percentage is around 18% at high heat input (0.813 kJ/mm) but decreases to about 14% with reduced heat input. Microhardness tests revealed that at the interface, the maximum value is reached at about 625 HV due to the presence of quenched martensite. Moreover, increasing the heat input favors wear resistance.

Use of DC Motor Control in Development of Pipe Welding Technology by Using the GMAW Process for Variation of Welding Nozzle Movement

Gas Metal Arc Welding (GMAW) welding technology is a welding method that is widely used in industry. A problem that often occurs is that it is difficult for a welder to control the speed of movement of the welding nozzle, which can affect the quality of the welding results. With welding tools that can control the movement of the welding nozzle, this problem can be overcome and increase the efficiency and productivity of the welding manufacturing process. The method for testing the quality of welding results is analyzed visually using the visual test and penetrant test methods. The use of GMAW welding tools for pipe butt joints using DC motor control to vary the movement of the welding nozzle is effective, making it easier for the welder and good welding results. Good welding results were obtained for setting the welding nozzle movement time in 1.4 seconds and 1 second for one left and right the movement cycle on a pipe joint rotating at a constant speed of 24 rpm. Setting the time for the welding nozzle movement in 0.6 seconds for one cycle of left and right movement produces poor welding in pipe joints that rotate at the same speed.

Arc and molten pool behavior on quality of hybrid cold metal transfer and tandem pulsed narrow gap gas metal arc welds: a study

ABSTRACT This research proposes a novel hybrid cold metal transfer (CMT) and tandem Pulsed gas metal arc welding (P-GMAW) process for narrow gap welding (NGW) of high strength low alloy (HSLA) steel plates. Investigating three sets of lead and trail wire feed speed (WFS) ratios [WFSL/T - 1.4, 1, 0.7], the study delves into the complex arc and metal transfer behavior within the narrow gap. Utilizing synchronized arc images and current-voltage waveforms, the research assesses their influence on fusion and mechanical properties. The root pass employs the single wire CMT process, while filling and closing passes leverage tandem P-GMAW, effectively minimizing incomplete fusion and reducing heat input. Results indicate that a lower WFSL/T (0.7) reduces the molten pool hump and overflow within the narrow gap while enabling direct weld arc engagement with the previously deposited layer, enhancing weld penetration. WFSL/T of 1.4 and 0.7 revealed higher and lower Charpy impact toughness.

Specification of the optimal gas metal arc welding (GMAW) parameters to enhance the mild steel strength (MS1018)

Arc fusion processes, such as high-efficiency gas metal arc welding (GMAW), have become increasingly prevalent in various industries. To optimize the GMAW parameters and enhance the strength of MS 1018, Monika and Chauhan conducted experiments using the low carbon steel filler wire (ER 70 S6). They used a Taguchi L9 OA (orthogonal array) to generate test data focusing on 3 GMAW parameters such as gas flow rate, arc voltage, and welding current. The performance characteristics considered were tensile strength (TS), weld zone hardness (WZH), and heat-affected zone hardness (HAZH). The effect of GMAW parameters investigated using the S/N (signal-to-noise ratio) transformation of individual test data, which is valid to account for variations observed in repeated tests. By conducting a thorough analysis of variance (ANOVA) on this transformed data, they were able to identify the optimal GMAW parameters for achieving high TS, WZH, and HAZH. Given that HAZH exhibited higher values than WZH, it was evident that TS had the most significant impact on the GMAW process. Consequently, the researchers established empirical relationships for TS, WZH, and HAZH in terms of the GMAW parameters. Their test data aligned reasonably well with the expected range of performance indicators, supporting the validity of their findings. Overall, Monika and Chauhan’s modified Taguchi approach, based on the L9 OA, allowed them to efficiently conduct a limited number of tests while obtaining comprehensive information on the optimal GMAW parameters for enhancing the strength of MS 1018.

Defects detection of GMAW process based on convolutional neural network algorithm

It is significant to predict welding quality during gas metal arc welding process. The welding defect detection algorithm has been developed based on convolutional neural network (CNN). The sensing system and image processing algorithm for molten pools has been developed. It overcomes the interference caused by the arc light to obtain clear images of the molten pool's boundaries. The molten pools images are used to build up training set and test set for training and testing the CNN model. The model is designed to extract the visual features of molten pool images to predict the penetration state, the welding crater, and slags. Through optimizing the network parameters such as kernel-size, batch-size and learning rate, the prediction accuracy is higher than 95%. Moreover, the model enhances additional focus on the welding crater based on the welder experience. The mechanisms between molten pool characteristics and welding defects were analyzed based on the welder experience and the visual features of the model. It is found that the model judges the occurrence of burn-through with the black hole in the middle zone of the molten pool. When the surface pores are generated, the model exhibits a strong response to circular voids in the semi-solid region at the trailing end of the molten pool. The size and shape of fusion holes exhibit a strong correlation with the molten state. When the shape of the crater does not appear concave, it often signifies excessive penetration. It contributes to enhancing the algorithm's robustness during various welding scenarios.

Image processing technique for measuring the weld dilution and heat-affected zone to model the gas metal arc welding process by a neuro-fuzzy system

Image processing technique for measuring the weld dilution and heat-affected zone to model the gas metal arc welding process by a neuro-fuzzy system

FOAMING THE 3D MODEL OF THE GAS METAL ARC WELDING PROCESS WITH THE HELP OF SOLID-WORKS AND EXAMINING THE STRESS

Today, in parallel with the rapid developments in every sector of the industry, various welding technologies are used for joining metal-based materials. In this article, a 3D model of the welding process was created with the help of SolidWorks program by using AISI 1020 and AISI 310 steel sheet brands and 2014-T4 Al electrode materials, which are suitable for the real mechanical properties of the alloys. Theoretically, the necessary modeling and stress calculations were made with the help of finite elements for the gas metal arc welding process. Keywords: SolidWorks, welding process, AISI 1020 steel sheet, AISI 310 steel sheet