Showing papers on "Gas metal arc welding published in 2022"

Effect of welding processes on mechanical and metallurgical characteristics of carbon steel cylindrical components made by wire arc additive manufacturing (WAAM) technique

Abstract: In recent decades, Additive Manufacturing (AM) has become a viable alternative to the manufacture of metal parts. Wire arc additive manufacturing (WAAM), a welding-based AM technique is an important research area since it permits the economical manufacture of large-scale parts with relatively high deposition rates. This article compares the effect of heat input on mechanical properties of carbon steel cylindrical components fabricated by Gas Metal Arc Welding (GMAW) and Cold Metal Transferred Arc Welding (CMTAW) processes. Firstly, the influence of heat input on the grain size was analysed. Subsequently, the effect of heat input on the tensile properties, impact toughness and hardness of the cylindrical components were studied along the building direction. The cylindrical component made by CMTAW process showed superior tensile properties and higher impact toughness than GMAW component. Similarly, CMTAW component exhibited higher hardness than GMAW cylindrical component. The variations in mechanical properties are mainly due to the appreciable variations that have occurred in the microstructural features and different grain sizes evolved at different heat input levels. The bottom and top regions of the fractured tensile and impact specimens of the components are characterised by dimple structures revealing the ductile fracture.

Experimental study on application of gas metal arc welding based regulated metal deposition technique for low alloy steel

Abstract: ABSTRACT In this work, a modified and advanced welding technique named regulated metal deposition (RMD) has been implemented for joining ASTM A387-11-2 low alloy steel plates. Mechanical behavior and microstructure of welded joints have been experimentally investigated after the recommended heat-treatment process. The microstructures of welded joints were examined using optical and scanning electron microscopes. Optical microscopy indicated the existence of bainitic and martensitic phases in the base material and weld zone, respectively. Scanning electron microscopy combined with energy dispersive x-ray analysis displayed the presence of martensitic colonies as well as deposits of carbide precipitates in both weldments. The mechanical properties of these weldments, namely micro-hardness, tensile strength, and impact strength were also investigated. A comparative study has also been carried out for the same material using the conventional gas metal arc welding, in which the microstructure and mechanical behavior of regulated metal deposition weldments have been compared to those of gas metal arc weldments. Regulated metal deposition weldments showed better mechanical behavior than the gas metal arc weldments for low alloy steel.

Experimental investigations on mechanical properties of multi-layered structure fabricated by GMAW-based WAAM of SS316L

Abstract: In the present study, the Gas metal arc welding (GMAW) based Wire-arc additive manufacturing (WAAM) process was used to fabricate a multi-layered structure at optimized process parameters on SS316L using metal wire of SS316L. The multi-layered structure's microstructure, macrostructure, and mechanical properties (tensile test, impact test, microhardness, and fractography) were examined at three locations at the top, middle, and bottom sides of the structure. Macrostructure at different zones has confirmed an appropriate bonding between the two layers, complete fusion without oxidation, and free from defects and unwanted geometries. Microstructure results have observed a colony of columnar dendrites in the bottom zone, coarser grains with vertical growth along with the residual ferrite in the middle zone, and vertical dendritic structure with residual ferrite in skeletal shape in the top zone. Results of all tensile properties for top, middle and bottom zone developed by the WAAM process fall in the range values of wrought SS 316 L. The microhardness values were shown a consistent behavior across the built structure in all three zones. The obtained average value for the impact test has shown better strength than commercially used wrought SS 316 L. The results of fractured tensile and fracture impact test specimens revealed many dimples, which suggests a good ductility of the as-built structure. Thus, the obtained results have shown that the built structure using the GMAW-based WAAM process matches the standards for industrial applications.

Effect of the welding technique on mechanical properties and metallurgical characteristics of the naval grade high strength low alloy steel joints produced by SMAW and GMAW

Abstract: Naval grade, high strength low alloy (HSLA) steel is designed especially for shipbuilding applications due to its high strength to weight ratio. The conventional fusion welding processes of shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) are employed widely for structural applications. This work reports the influence of welding processes on mechanical properties and metallurgical characteristics of fusion welded DMR249A grade steel. The evaluating tensile, impact, microhardness properties were correlated with microstructures. The maximum recorded transverse tensile strength value of SMAW and GMAW joints were 558 MPa and 578 MPa. The lower microhardness had obtained in the subcritical heat-affected zone than other regions. The weld zone microstructure consists of fine, elongated, and columnar grain structures. From this investigation, it has been concluded that GMAW joints displayed marginally better properties than SMAW joints. But most weld failures has been observed in the subcritical heat-affected region; due to grain deformation and subsequent softening in the weldment.

Optimization of Bead Morphology for GMAW-Based Wire-Arc Additive Manufacturing of 2.25 Cr-1.0 Mo Steel Using Metal-Cored Wires

Abstract: The fabrication of components involves the deposition of multiple beads in multiple layers for wire-arc additive manufacturing (WAAM). WAAM performed using gas metal arc welding (GMAW) allows for the manufacturing of parts through multiple-bead multi-layer deposition, which depends on the process variables. Thus, the selection of process parameters along with their required levels is mandatory to deposit multiple layers for WAAM. To obtain the desired levels of parameters, bead-on-plate trials were taken on the base plate of low alloy steel by following an experimental matrix produced through the Box–Behnken design (BBD) on GMAW-based WAAM. Wire feed speed, travel speed, and voltage were chosen as the input parameters and bead width and bead height were chosen as the output parameters. Furthermore, the robustness and adequacy of the obtained regression equations were analyzed by using analysis of variance (ANOVA). For both responses of BW and BH, values of R2 and adj. R2 were found to be near unity, which has shown the fitness of the model. Teaching–learning-based optimization (TLBO) technique was then employed for optimization. Within the selected range of process variables, the single-objective optimization result showed a maximum bead height (BH) of 7.81 mm, and a minimum bead width (BW) of 4.73 mm. To tackle the contradicting nature of responses, Pareto fronts were also generated, which provides a unique non-dominated solution. Validation trials were also conducted to reveal the ability and suitability of the TLBO algorithm. The discrepancy between the anticipated and measured values was observed to be negligible, with a deviation of less than 5% for all the validation trials. This demonstrates the success of the established model and TLBO algorithm. The optimum feasible settings for multi-layer metal deposition were determined after further tuning. A multi-layer structure free from any disbonding was successfully manufactured at the optimized variables. The authors suggest that the optimum parametric settings would be beneficial for the deposition of layer-by-layer weld beads for additive manufacturing of components.

Thermal expansion behaviour of Invar 36 alloy parts fabricated by wire-arc additive manufacturing

Abstract: Invar 36 alloy is of high interest in various industrial sectors, due to its reduced thermal expansion properties. This study aims to validate Wire-Arc Additive Manufacturing (WAAM) technology as a valid method for manufacturing aerospace tooling in Invar 36. The main novelty and the objective of this work is to study the properties of Invar deposited by WAAM technology and to provide guidelines for the manufacture of parts using this technology. To do so, the thermal expansion behaviour of Invar specimens manufactured using Gas Metal Arc Welding (GMAW)-based WAAM technology and Plasma Arc Welding (PAW)-based WAAM technology is analyzed for subsequent comparison with the values obtained from the laminated Invar sample used as the reference specimen. A wall is manufactured with each technology, for comparative purposes, from which specimens were extracted for the dilatometry test and metallographic analysis. The results of these analyses show the advantages of GMAW technology for the manufacture of Invar alloy parts, as it presents the same thermal expansion behaviour as the laminated reference material with less presence of precipitates and no macrostructural failures such as pores, cracks and lacks of fusion. Furthermore, to conclude, an aeronautical tooling that has been manufactured within this work demonstrated the potential of this technology to manufacture specialized aeronautical parts.

Advanced High-Strength Steels for Automotive Applications: Arc and Laser Welding Process, Properties, and Challenges

Abstract: In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS.

Effect of the Heat Input on Wire-Arc Additive Manufacturing of Invar 36 Alloy: Microstructure and Mechanical Properties

Abstract: Abstract Invar, also known as FeNi36, is a material of great interest due to its unique properties, which makes it an excellent alternative for sectors such as tooling in aeronautics and aerospace. Its manufacture by means of wire arc additive manufacturing (WAAM) technology could extend its use. This paper aims to evaluate the comparison of two of the most widespread WAAM technologies: plasma arc welding (PAW) and gas metal arc welding (GMAW). This comparison is based on the analysis of wall geometry, metallography, and mechanical properties of the material produced by both technologies. The results show a slight increase in toughness and elongation before fracture and worse tensile strength data in the case of PAW, with average values of 485 MPa for ultimate tensile strength (UTS), 31% for elongation and 475 MPa, 40% in GMAW and PAW, respectively. All results gathered from the analysis show the possibility of successful manufacturing of Invar by means of WAAM technologies. The novelties presented in this paper allow us to establish relationships between the thermal input of the process itself and the mechanical and metallographic properties of the material produced.

Parametric Study and Investigations of Bead Geometries of GMAW-Based Wire–Arc Additive Manufacturing of 316L Stainless Steels

Abstract: Appropriate selection of wire–arc additive manufacturing (WAAM) variables imparts bead geometries with characteristics of multi-layer structures. Thus, the present study aimed to optimize the gas metal arc welding (GMAW)-based WAAM variables of travel speed (TS), wire feed speed (WFS), and voltage (V) for the bead geometries of bead width (BW) and bead height (BH) on an SS 316L substrate. Single-layer depositions were made through a metallic wire of SS 316L by following an experimental matrix of the Box–Behnken design (BBD) technique. Multivariable regression equations were generated for design variables and responses, and ANOVA was used to investigate the feasibility of the obtained regression equations. WFS was the highest contributor affecting the BW, followed by V and TS, while WFS was again the highest contributor affecting the BH, followed by TS and V. Heat transfer search (HTS) optimization was used to attain optimal combinations. The single-objective optimization result showed a maximum bead height and minimum bead width of 6.72 mm and 3.72 mm, respectively. A multi-layer structure was then fabricated by considering an optimization case study, and it showed optimized parameters at a WFS of 5.50 m/min, TS of 141 mm/min, and voltage of 19 V with the bead height and bead width of 5.01 mm and 7.81 mm, respectively. The multi-layered structure obtained at the optimized parameter was found to be free from disbonding, and seamless fusion was detected between the obtained layers of the structure. The authors believe that the present study will be beneficial for industrial applications for the fabrication of multi-layer structures.

On the Influence of Linear Energy/Heat Input Coefficient on Hardness and Weld Bead Geometry in Chromium-Rich Stringer GMAW Coatings

Abstract: Wear of the working surfaces of machinery parts is a phenomenon that cannot be fully countered, only postponed. Among surface lifecycle elongation techniques, hardfacing is one which is most often used in heavy load applications. Hardfaced coating can be applied using different welding approaches or thermal spraying technologies, which differ when it comes to weld bead dimensional precision, layer thickness, process efficiency and material. In this study the authors examine the geometrical behavior and hardness properties of two distinctive chromium-based Gas Metal Arc Welding (GMAW) cored wires. The stringer beads are applied numerically with five levels of linear energy, being a resultant of typical values of welding speed and wire feed, ranging between 250 mm/s to 1250 mm/s (welding speed) and 2 m/min to 10 m/min (wire feed). The samples were cut, etched and measured using a digital microscope and Vickers indenter, additionally the chemical composition was also examined. Hardness was measured at five points in each cutout, giving 40 measurements per sample. The values were analyzed using an ANOVA test as a statistical background in order to emphasize the divergent behavior of the cored wires. It appeared that, despite having less chromium in its chemical composition, wire DO*351 exhibits higher hardness values; however, DO*332 tends to have a more stable geometry across all of the heat input levels.

A study on tensile properties and microstructural characteristics of wire arc additive manufactured low carbon steel cylindrical components

Abstract: Abstract Wire arc additive manufacturing (WAAM) is an additive manufacturing (AM) technology that uses a modified robotic arc welding machine to manufacture parts in a layer-by-layer pattern. Wire-based AM has many major advantages, including good fabrication flexibility and control, as well as easier automated manufacturing. This article compares the tensile proprieties of WAAM low carbon steel cylinders made by pulsed current gas metal arc welding (PGMAW) and pulsed current cold metal transfer (PCMT) arc welding techniques. The microhardness and tensile properties of the WAAM cylindrical parts were evaluated in the bottom and top zones. The PCMT-WAAM cylinder showed higher hardness, yield strength (YS), and ultimate tensile strength (UTS) than the PGMAW-WAAM cylinder. The microstructural characteristics of the produced low carbon steel cylinders varied from one process to another process. The inhomogeneity in tensile properties and hardness is caused by variations in microstructural characteristics.

Additive manufacturing of a bridge in situ

Abstract: Nominated for Eurosteel 2021 Best Paper Award

Deep Neural Networks for Defects Detection in Gas Metal Arc Welding

Abstract: Welding is one of the most complex industrial processes because it is challenging to model, control, and inspect. In particular, the quality inspection process is critical because it is a complex and time-consuming activity. This research aims to propose a system of online inspection of the quality of the welded items with gas metal arc welding (GMAW) technology through the use of neural networks to speed up the inspection process. In particular, following experimental tests, the deviations of the welding parameters—such as current, voltage, and welding speed—from the Welding Procedure Specification was used to train a fully connected deep neural network, once labels have been obtained for each weld seam of a multi-pass welding procedure through non-destructive testing, which made it possible to find a correspondence between welding defects (e.g., porosity, lack of penetrations, etc.) and process parameters. The final results have shown an accuracy greater than 93% in defects classification and an inference time of less than 150 ms, which allow us to use this method for real-time purposes. Furthermore in this work networks were trained to reach a smaller false positive rate for the classification task on test data, to reduce the presence of faulty parts among non-defective parts.

Analysis of metal transfer and weld forming characteristics in triple-wire gas indirect arc welding

Abstract: Triple-wire gas indirect arc welding (TW-GIA) has the advantages of low heat input and high deposition rate. However, the simultaneous melting of triple wires makes the metal transfer mode complicated. The unknown of the metal transfer mode restricts the development of this technology. In this paper, high-speed camera systems and electrical signal acquisition sensors were used to explore the TW-GIA metal transfer mode. The static force model and the arc conductive channel model were used to discuss the droplet force and energy conversion characteristics, respectively. Results showed that the TW-GIA metal transfer modes can be divided into the following: short-circuit transfer (SCT), main wire projected transfer + side wire globular transfer (PGT), main wire streaming transfer + side wire projected transfer (SPT), and main wire streaming transfer + side wire streaming transfer (SST). Moreover, the process parameter ranges corresponding to the four modes were summarized. Due to the stable arc and the uniform metal transfer process, SPT and SST can form desirable weld seam. The gravity and z-axis components of electromagnetic force are the main forces that promote metal transfer. The x-axis and y-axis components of the electromagnetic force deviate the metal transfer path from the arc coverage. Due to the change of arc conductive channel, the energy transferred from TW-GIA to the base metal is less than that of gas metal arc welding, showing the advantages of small welding deformation, narrow heat-affected zone, and grain refinement.

Finite element analysis and experimental investigation of moving heat source model for GMAW deposited mild steel weld bead

Abstract: An investigation has been done to identify the heat source model suitable for numerical modeling of the Gas Metal arc Welding (GMAW) welding process. In the present investigation, a numerical model was constructed to simulate the GMAW welding process through transient thermal analysis for different thermal heat source models for weld deposition of Mild steel considering semi-cylindrical weld bead geometry. The Gaussian heat source with radial coordinate system and double ellipsoidal thermal heat source have been considered to develop a Finite Element Analysis (FEA) model. Validation of numerical analysis results has been confirmed through experimental investigation. Numerical modeling confirms the utilization of both heat sources, i.e. Gaussian and Double ellipsoidal for the prediction of the weld bead deposition profile. However, the numerical modeling developed using a double ellipsoidal heat source has more resembles experimental investigation due to the utilization of bead profile data. However, the Gaussian heat source is found to be suitable in the case of the unavailability of experimental data. The experimental studies show a variation in the weld bead geometry, along its welding direction due to multiple environmental factors. The microstructural investigation also shows the development of a fine columnar grain structure at the welding bead & weld penetration zone, and the grain structure became coarser at the Heat Affected Zone (HAZ).