Pulsed Metal Inert Gas Research Articles

Influence of the Pulse Mode of Manual Metal Arc Welding on Weldment Distortions.

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder.

Effect of filler wires on microstructure and mechanical properties of Inconel 718 welded joints by double pulse metal inert gas welding

ABSTRACT Inconel 718 possesses issues like microsegregation of Nb, Mo leads to the formation of Laves phase which degrades the mechanical properties of the welded joints. This study aims to investigate the mechanical properties and microstructural characteristics of Inconel 718 welded joints using the double pulse metal inert gas (DP-MIG) process by the combined effect of filler wires, such as ERNiFeCr-2, ERNiCrCoMo-1, and 9Cr-1Mo. All the weldments were found to have columnar dendrites with coarser grain morphology. Liquated grain boundaries, secondary phases, unmixed zones at the heat affected zone (HAZ) and segregation of Nb (21.3%) and Mo (10.4%) at the weld zone were identified for ERNiFeCr-2 and ERNiCrCoMo-1 fillers. From EBSD findings, the formation of peninsula and island at the HAZ and segregation of Fe (68%) in the weld zone of 9Cr-1Mo filler weldment was noticed. Even though the ultimate tensile strength (UTS) of all the weldments was found to be inferior to that of base metal (788.9MPa), the 9Cr-1Mo filler weldment shows better tensile strength of 403.5MPa with a joint efficiency of (51.14%). From the fractography results, the void formation due to secondary phases along with dimple networks ensures the ductility mode of fracture for all the weldments.

Experimental Investigation of Mechanical Properties and Characterization of Mild Steel Weldment Fabricated Using Pulse/Robotic Pulse Metal Inert Gas Welding Processes

Experimental Investigation of Mechanical Properties and Characterization of Mild Steel Weldment Fabricated Using Pulse/Robotic Pulse Metal Inert Gas Welding Processes

Effect of double-pulse frequency and post-weld heat treatment on microstructure and mechanical properties of metal-inert gas welded Al–Mg–Si alloy joints

The Al–Mg–Si alloy welded structure is widely used in aerospace, marine ship, automotive and other industries. However, the mechanical properties of welded joint were seriously weakened due to the microstructure coarsening and heat affected zone (HAZ) softening, making its service life decayed. In this paper, in order to enhance the mechanical properties of Al–Mg–Si alloy welded joint, a coupled method including double pulsed Metal Inert Gas (DP-MIG) welding technology and post-weld heat treatment (PWHT) were applied on the joining process of Al–Mg–Si alloy. With the increase of DP frequency from 2 Hz to 5 Hz, the average grain size of fusion zone decreased from 113.7 μm to 88.4 μm. And the tensile strength of welded joint was at the interval of 180∼190 MPa. After a suitable heat treatment (solution treatment at 530 °C for 2 h and aging treatment at 180 °C for 8 h), the tensile strength of welded joint increased to 318.3–333.8 MPa, which exceeds 90 % of the base metal (BM). Under the comprehensive effect of solid solution strengthening, fine grain strengthening, and precipitation strengthening, the mechanical properties of Al–Mg–Si alloy welded joint were significantly improved. And the research results in this paper can provide a research basis for high quality connection of Al–Mg–Si alloys.

Enhancing tensile properties of MIG welded AA6061 joints: Effect of pulse mode and post-weld heat treatment

Metal-Inert Gas (MIG) welding is one of the most important welding technologies commonly used in the manufacturing industry due to its high degree of automation and welding adaptability. However, softening is prone to occur in fusion zone (FZ) and heat affected zone (HAZ) of AA6061 MIG welded joint, which limits its application. In this work, AA6061 was welded by MIG welding with different pulse modes, and the post-welding heat treatment was carried out. The results show that the dual pulse MIG (DP-MIG) and PWHT can significantly improve the mechanical properties of AA6061 butt joint, and its ultimate tensile strength (UTS) is 331.3 MPa, even more than 90% of the base material (BM). In this paper, the microstructure of welded joints under different pulse conditions before and after PWHT was compared, and the relationship between the welding process, microstructure, and mechanical properties was established Furthermore, the influence mechanisms of pulse mode and PWHT on the mechanical properties of welded joints were explained in detail.

Multicriteria decision-making for optimization of welding parameters in cold metal transfer and pulse metal-inert gas weld bead of AA2099-T86 alloy using CRITIC and ROV methods

PurposeThe criteria importance through intercriteria correlation (CRITIC) and range of value (ROV) combined methods were used to determine a single index for all multiple responses.Design/methodology/approachThis paper used cold metal transfer (CMT) and pulse metal-inert gas (MIG) welding processes to study the weld-on-bead geometry of AA2099-T86 alloy. This study used Taguchi's approach to find the optimal setting of the input welding parameters. The welding current, welding speed and contact-tip-to workpiece distance were the input welding parameters for finding the output responses, i.e. weld penetration, dilution and heat input. The L9 orthogonal array of Taguchi's approach was used to find out the optimal setting of the input parameters.FindingsThe optimal input welding parameters were determined with combined output responses. The predicted optimum welding input parameters were validated through confirmation tests. Analysis of variance showed that welding speed is the most influential factor in determining the weld bead geometry of the CMT and pulse MIG welding techniques.Originality/valueThe heat input and weld bead geometry are compared in both welding processes. The CMT welding samples show superior defect-free weld beads than pulse MIG welding due to lesser heat input and lesser dilution.

A comparative study on weld-bead geometry of austenitic stainless-steel produced by cold metal transfer welding and pulse metal inert gas welding process

In recent years, weld cladding has become an emerging technique for the surface modification of carbon steel, which has various industrial applications such as chemical, marine, mining, agriculture, and power generation. In this research, cold metal transfer (CMT) welding and pulse metal inert gas (MIG) welding are utilized to study the weld-clad bead of 308L stainless steel over low-carbon steel. To examine the mechanical and wear characteristics of CMT weld-clad samples, welding speed (3, 4, 5, and 6 mm/s) was used as the input process parameter, while current (175 A), nozzle to workpiece distance (10 mm), and shielding gas flow rate (15 l/min) were kept constant. Microstructural analysis of weld bead samples was done through optical microscopy and field emission scanning electron microscopy. With an increase in welding speed, the microhardness and wear properties of the clad surface were improved. The CMT-clad surface had significant improvements in mechanical, wear properties, and lower residual stresses due to low dilution and lesser heat input.

Effect of heat input on corrosion behavior of automotive zinc-coated steel joint

Abstract Lately, coated steel sheets have replaced bare steel in the automotive sectors due to their corrosion protection. Among them, zinc-coated high strength interstitial free (HIF) steel is widely used due to its durability, formability, good surface finish, impact resistance, and corrosion resistance. However, joining galvannealed (GA) steel using conventional fusion welding processes is challenging as it results in porosity and potentially harmful fumes. To overcome these challenges, this work uses a pulse MIG (metal inert gas) brazing technique to join the HIF-GA steel sheet with a lap joint configuration utilizing Cu-Si base filler wire (CuSi3Mn1) in an argon atmosphere. The study aims to evaluate the effect of heat input on bead geometry and Zn degradation in MIG brazed joints by adjusting the current from 40 to 60 A and brazing speed from 400 to 500 mm min−1. It is observed that the heat input is inversely proportional to the wetting angle and directly proportional to the bead width, leg length, and cross-sectional area. Heat input influences Zn degradation on both the front (at the toe) and back sides of the lap joint. The corrosion behavior of joints is studied using an electrochemical test (in 3.5% NaCl solution) and a salt spray test (in 5% NaCl solution). Further, the Zn degradation is analyzed with EDS line scanning to understand the corrosion resistance of the MIG brazed joints. A potentiostatic polarization study is also conducted to determine the corrosion rate using a Tafel plot. It is found that the lowest corrosion rate in base metal (BM) increased from 0.88 to 12.26 mm year−1 with the increase in heat input from 61 to 113 J mm−1.

Effect of P-MIG and CMT on microstructure and properties of 6082-T6 joints

This paper focuses on pulse metal inert gas welding (P-MIG) and cold metal transfer (CMT) of 6082-T6 aluminium alloy. The microstructure and properties of joints were analysed and the phase transformation of the welding zones (WZ) was calculated using JMatPro. The results showed that CMT joints are better than P-MIG joints in tensile strength and hardness. The main reason is that the average grain size and the second phase size of CMT joints are smaller than those of P-MIG joints. Moreover, the larger number of large-angle grain boundaries (LAGB), diffusely distributed Al3Mg2 and Al6Mn phases in CMT WZ, as well as a small amount of distributed Al3Zr, are beneficial to the joints properties too.

Experimental evaluation of longitudinal tensile properties of ferritic stainless-steel weldment joined by metal inert gas, pulse metal inert gas, and tungsten inert gas welding

In this work, ferritic stainless steel (FSS) weldments were prepared by tungsten inert gas (TIG), metal inert gas (MIG), and pulsed-MIG welding. Pure argon and a mixture of argon + 2% oxygen were utilized as shielding gas in each type of welding. The FSS (ER430) and austenitic stainless steel (ASS) (ER309L) wires were used as filler consumable wires during all the three types of welding. The effects of varying welding processes, shielding gases, and consumable electrodes on the longitudinal tensile properties of weldments were investigated. The universal tensile testing machine was used to evaluate longitudinal ultimate tensile strength and percentage elongation experimentally in each case. The maximum tensile strength of FSS weldment was obtained in the case of (Ar + 2% O2) mixture of shielding gas and ASS filler wire in each welding process. Heat treatment was also carried out for samples prepared by MIG and TIG welding. The reduction in tensile strength and enhancement in percentage elongation was observed for both MIG and TIG welding after heat treatment.

Effect of Single and Double Pulse MIG Welding Process Parameters on Microstructure and Properties of Aluminium Alloy

Lightweight aluminium alloys are widely used in many industries due to their advantageous mechanical properties. As welding is a popular method for joining aluminium alloy sheets, it is important to understand how the welding process affects the alloy’s performance. Here, we investigated the influence of various operating parameters during pulsed metal inert gas (MIG) welding of thin aluminium alloy plates on the input energy and metallurgical microstructure of the weld. A series of welding tests were performed using surface welding of AA6061 aluminium alloy plates under conditions of a single strong-pulse, single weak-pulse, or double pulse. The morphology, metallurgical structure, and hardness of the welds produced using the different welding parameters were then examined. We observed that increasing the welding speed and the arc duration of low-energy pulses can reduce the heat input. Lower heat input is advantageous as it results in a higher cooling rate of the welding pool and a smaller average grain size of the weld structure. In addition, increasing the welding speed increased the hardness of the weld. Double pulsed MIG welding showed the best overall weld performance and is recommended for improving the quality of aluminium alloy bonding.

Effect of pulse mode and frequency on microstructure and properties of 2219 aluminum alloy by ultrahigh-frequency pulse Metal-Inert Gas Welding

Based on self-developed ultra high frequency pulse Metal-Inert Gas Welding (UFP-MIG) power source, the ultra-high frequency pulse (UFP) current was studied as an effective way for improving the microstructure and properties of 2219 aluminum alloy joints. The welding pores reduction performance, microstructures, microhardness, and tensile properties of conventional pulsed MIG(CP-MIG) welds and the UFP-MIG welds with different modes and frequencies were investigated. The results indicated that the UFP-MIG process could almost completely eliminate welding porosity in the joints of 2219 aluminum alloy. Compared with CP-MIG welding process, the grain size of the UFP-MIG welding zone was reduced and gradually decreased as the frequency of UFP increased. Similarly, the grain refinement effect also appeared in the heat affected zone (HAZ) near the welds, and the grain size could be reduced by up to 14.85%. Meanwhile, the morphology and uniformity of θ phases and α+θ eutectics along grain boundaries of UFP-MIG welds were also improved. The microhardness in the weld zone and partially melted zone (PMZ) of UFP-MIG weld joints with different modes and frequencies were significantly improved. The highest joint average microhardness occurred at peak pulse mode (PP) with 40 kHz(75.17HV), which was 27.9% higher than that of CP-MIG (58.74HV). The strength and ductility of welded joints were simultaneously improved by UFP-MIG weld process. Fracture analysis results showed that the large reduction of weld pores, the refinement of weld grains, and the lower segregation of Cu element in the eutectic were responsible for the joint tensile properties improvement.

Progress in the arc plasma temperature measurement and its finite element analysis in pulsed MIG welding process

The article focuses on the state of the art review of progress in the arc plasma temperature measurement, a lesser-explored area of pulsed metal inert gas welding because of technological and economic constraints. However, investigation of the arc plasma temperature is paramount for precise prediction in welding process simulation models. The dynamic behavior of arc plasma in the pulsed MIG welding process is a multifaceted heat mass transfer phenomenon involving chemical, electro-magnetic, and fluid dynamics.In the pulsed MIG welding process thermal, mechanical, and electrical phenomenon co-exists and results in the formation of all four states of matter in a very small fusion sphere. The paper throws light on the latest investigations on the importance of precise measurement of arc plasma temperature, techniques used for measurement of the arc plasma, and challenges associated with pulsed MIG welding. Moreover, unanswered characteristics of the welding fusion sphere with future directions are discussed in the challenges section. It will serve as a guide to researchers and industry for developing better insight for performing pulsed MIG welding, developing accurate numerical models of pulsed MIG welding, and will also provide sufficient base to focus on thrust area of pulsed MIG welding.

Feature Extraction of Double Pulse Metal Inert Gas Welding Based on Broadband Mode Decomposition and Locality Preserving Projection

A novel adaptive signal decomposition algorithm, broadband mode decomposition (BMD), is proposed for analyzing nonstationary broadband signals. Unavoidable error will occur when applying former time-frequency methods to broadband signals, which is caused by Gibbs phenomenon and the calculation of extrema. To overcome that problem, BMD is proposed by searching in the associative dictionary that contains both broadband and narrowband signals. The procedure of the proposed method is as follows: First, the collected datasets are analyzed by BMD and the composite multiscale fuzzy entropies (CMFEs) of the obtained effective components are calculated. Then, locality preserving projection (LPP) is applied for further feature extraction. Analysis results show BMD is more effective when drawing broadband feature from noise and BMD is adaptive for the quality monitoring of DPMIG welding.

Influence of deposition strategy of structural interface on microstructures and mechanical properties of additively manufactured Al alloy

Mechanical properties of the structural interface are significantly important for the wire + arc additively manufactured (WAAM) component who keeps the substrate as a part. Two deposition strategies using power sources of pulse advanced cold metal transfer (CMT-PA) and pulse metal inert gas (MIG-P) as the first layer were designed to build WAAM 2319 Al alloy walls. The microstructure and mechanical properties of the structural interfaces and the entire parts were investigated. Key findings demonstrated the deposition strategy has little influence on the macro-mechanical properties of the WAAM parts. All the as-deposited parts were fractured on the WAAM metal 5–7 layers away from the interface boundary, although the bottoming arc mode had a great influence on the geometry and microstructure of the interfaces. Microcracks were initiated from the micropores or coarse θ particles. After the T6 heat treatment, the entire WAAM part containing the substrate exhibited a homogeneous feature of mechanical properties. The mean yield stress and ultimate tensile stress achieved over 330 MPa and 430 MPa due to the precipitation of a considerable number of nano-sized metastable θ′ phases. Whereas the bottoming strategy of MIG-P, which will effectively enlarge the load-bearing area and increase materials utilization rate, is suggested during the design of WAAM components.

Comparative Study of Laser-Arc Hybrid Welding for AA6082-T6 Aluminum Alloy with Two Different Arc Modes

The effects of arc modes on laser-arc hybrid welding for AA6082-T6 aluminum alloy were comparatively studied. Two arc modes were employed: pulsed metal inert gas arc and cold metal transfer arc. The results indicated that joints without porosity, undercutting, or other defects were obtained with both laser-pulsed metal inert gas hybrid welding (LPMHW) and laser-cold metal transfer hybrid welding (LCHW). Spatter was reduced, and even disappeared, during the LCHW process. The sizes of equiaxed dendrites and the width of the partially melted zone in the LPMHW joint were larger than those in the LCHW joint. The microhardness in each zone of the LPMHW joint was lower than that of the LCHW joint. The softening region in the heat-affected zone of the LPMHW joint was wider than that of the LCHW joint. The tensile strength of the LCHW joint was higher than that of the LPMHW joint. For the two joints, the fractures all occurred in the softening region in the heat-affected zone, and the fracture morphologies showed ductile fracture features. The dimples in the fractograph of the LCHW joint were deeper than those of the LPMHW joint.

Quality monitoring of aluminum alloy DPMIG welding based on broadband mode decomposition and MMC-FCH

In double pulse metal inert gas (DPMIG) welding, the input broadband electrical signals are often affected by strong noise, which will decrease the quality monitoring accuracy. Therefore, a suitable method should be applied to extract features from the signals. However, due to the Gibbs phenomenon and the interpolation of extreme points, former methods such as variational mode decomposition (VMD) and ensemble empirical mode decomposition (EEMD) will generate unavoidable error. Therefore, broadband mode decomposition (BMD) method is newly proposed in this paper by constructing an associative dictionary library consisting of typical broadband and narrowband signals. Therefore, the drawbacks of the former methods can be avoided by searching in the dictionary. Analysis results indicate that by combining with flexible convex hulls (MMC-FCH), BMD is more accurate in extracting broadband components. Meanwhile, the mean accuracy of quality monitoring can be increased from 92.19% (VMD) and 93.75% (EEMD) to 100% by applying BMD.

Effect of pulsed metal inert gas (pulsed-MIG) and cold metal transfer (CMT) techniques on hydrogen dissolution in wire arc additive manufacturing (WAAM) of aluminium

Aluminium is one of the most experimented metals in the WAAM field owing to a wide range of applications in the automotive sector. Due to concerns over reduction of strength, elimination of porosity from wire arc additive manufactured aluminium is one of the major challenges. In line with this, the current investigation presents findings on hydrogen dissolution in solid aluminium and hydrogen consumed to form porosity along with its distribution as a function of heat inputs and interlayer temperatures in a WAAM 5183 aluminium alloy. Two varieties of WAAM, pulsed metal inert gas (MIG) and cold metal transfer (CMT), were explored. Samples made with pulsed metal inert gas (pulsed-MIG) process picked up more hydrogen compared to samples produced by cold metal transfer technique. Correspondingly, pulsed-MIG samples showed increased number of pores and volume fraction of porosity than samples manufactured using the cold metal transfer (CMT) technique for different heat input and interlayer temperature conditions. However, CMT samples exhibited higher amount of dissolved hydrogen in solid solution compared to pulsed-MIG process. In addition, heat input, interlayer temperature, and interlayer dwell time also played a key role in pore formation and distribution in WAAM-produced aluminium 5183 alloy.

Modulated Broadband Mode Decomposition for the Feature Extraction of Double Pulse Metal Inert Gas Welding

Modulated Broadband Mode Decomposition for the Feature Extraction of Double Pulse Metal Inert Gas Welding

Formability behavior of Al/steel MIG arc brazed-fusion welded joint

5052 Al alloy plate was successfully lap-joined to galvanized steel plate by pulsed metal inert gas (MIG) arc welding with Al-Si filler wire. Formability properties of the Al/steel brazed-fusion welded joints with different welding parameters were characterized and investigated by bending and cupping tests. Sound weld appearance was obtained for all the fusion welded-brazed joint of aluminum alloy to steel in experiments, the average mechanical resistance of the joints reached up to 80% or so of that of the Al alloy base metal. The largest longitudinal face bending angle was 108°. There was an evident negative relationship between the welding heat input and the joint bending property. The formation of Fe2Al5Zn0.4 of intermetallic compounds (IMCs) at the brazed interface was an important influencing factor on the bending property of the joints. Based on the IMCs layer morphology, the fracture modes in bending tests were analyzed by three different paths of crack propagation owing to different welding heat inputs. During the cupping tests, surface crack initiation occurred in the heat-affected zone of the Al alloy side at welding heat input of 592 J/cm and the bulging drawing property was equivalent to that of the Al alloy base metal. The studies indicated the possibility and feasibility of manufacturing TWBs by the MIG brazed-fusion welding of Al alloy to steel.