Pulsed Metal Inert Gas Welding 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.

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 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.

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.

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.

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

A gradient Al/Ni-Cr-Al layer formed by direct current pulse metal inert gas welding combined laser cladding on AZ91D magnesium alloy

A gradient modified layer, containing an Al-Si interlayer and a Ni-Cr-Al top layer, was formed by direct current pulse metal inert gas welding combined laser cladding on AZ91D magnesium alloy. Firstly, the direct current pulse metal inert gas welding was used to prepare an interlayer with enough thickness on the surface of AZ91D magnesium alloy. After that, a pulsed YAG laser was applied to clad Ni-Cr-Al powders on the interlayer to form a top modified layer with higher micro-hardness and better corrosion resistance. The SEM, EDS and XRD results show that the interlayer is mainly composed of α-Al, Al + Al3Mg2 and Mg2Si while the top layer is mainly composed of α-Al, Al3Ni, Al45Cr7, Mg2Si and Al + Al3Mg2. Furthermore, Y2O3 was added to ameliorate the microstructure and properties of the gradient layer. The addition of Y2O3 could refine the grain size, forming uniform microstructure in the top layer. The micro-hardness of the top layer is about five times higher than that of the AZ91D substrate and two times higher than that of the interlayer. The micro-hardness and corrosion resistance of the top layer were enhanced with the addition of Y2O3.

Active vision sensing and feedback control of back penetration for thin sheet aluminum alloy in pulsed MIG suspension welding

Consistent penetration control of thin sheet aluminum alloy in automatic pulsed metal inert gas (MIG) welding can help ensure its welding quality. In this research, a novel active vision sensing system consisting of a camera and an auxiliary light source has been designed for back penetration monitoring in pulsed MIG suspension welding for aluminum alloy, possessing the ability of intensifying weld seam features and anti-interference to arc lights. Corresponding image processing algorithms were developed to suppress noises and calculate back width of weld pool. Then a fuzzy controller was proposed to control back penetration of aluminum alloy in pulsed MIG suspension welding by means of adjusting the welding current. Butt welding and variable heat dissipation tests under constant welding current and closed-loop control demonstrated that the closed-loop controller can solve the lack of penetration issue during the welding process and can prevent increased back width when the heat dissipation conditions are deteriorated. Furthermore, the maximum deviation between the detected and given width can be controlled to be within ±0.5 mm in these tests, and mean square deviations were less than 0.32, which is acceptable for weld formation control.

Effect of Applied Energy on the Microstructure, Texture, and Mechanical Properties of Short-Circuit Metal Inert Gas-Welded Modified Cr-Mo Steel Joints

Modified 9Cr-1Mo is a ferritic-martensitic steel widely used in steam generators of fast breeder reactors in the nuclear industry due to their enhanced creep resistance. In the present investigation, P91 steel was welded without preheat using three different heat inputs by pulsed short-circuit metal inert gas welding process using a ER90S-B9 wire electrode for the first time. The microstructural developments were characterized by using optical and electron microscopy, while the residual stresses were measured by X-ray diffraction using the sin2ψ method. The grain size variation in the fusion zone/heat-affected zone was effectively studied using electron backscattered diffraction to bring out the changes quantitatively. The weld zone had a consistent texture, while the heat-affected zone was random. The grain size tends to increase with the increase in heat input which leads to reduced joint strength. It is evident that at highest heat input, the weld microstructure shows substantial precipitation of M23C6-type carbides. The residual stresses were near compressive in the weld-HAZ, while maximum tensile stresses were found for the highest heat input.

Pulse MIG Welding of 6061-T6/A356-T6 Aluminum Alloy Dissimilar T-joint

Dissimilar T-joints between 4-mm-thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates are made with pulse metal inert gas welding (P-MIG) process, and the weld geometry, microstructure and mechanical properties of the joints are investigated. The average tensile load of the joints is 9488 N at travel speed 12 mm/s and welding current 165 A with 6061 aluminum alloy as web plate and A356 aluminum alloy as flange plate. The weld zone (WZ) is composed of dendrite zone and columnar zone, which is wide at bottom of weld making it become a weak zone. Besides, grain boundary (GB) liquation, consisting of GB eutectic and solute-depleted α-Al, occurs in the partially melted zone on 6061 aluminum alloy side. The T-joint with highest tensile load fails at the root of WZ and the flange plate near the weld with different fracture modes.

Characterisation of microstructure, mechanical and corrosion properties of pulsed MIG welded modified P91 steel weld metal

Varying the shielding gas composition with argon and carbon dioxide influences the properties of the weldments which are evaluated using microstructural, micro-hardness and corrosion studies. The modified P91 steel samples are welded by Pulsed Metal Inert Gas welding process with different shielding gas mixture, i.e., 95%Ar-5%CO2, 80%Ar-20%CO2 and 60%Ar- 40%CO2. The welded steels are studied metallographically by observing microstructures at three different regions namely at the base metal, Heat Affected Zone (HAZ) and the Weld zone. Hardness measurements are also done using Vicker’s micro-hardness tester. Corrosion studies in acidic media (sulphuric and nitric acid media of four different normalities 0.5, 1.0,1.5 and 2.0) are done in the welded region and the parent metal to compare the corrosion resistance. Of all the welded samples, welds made with the shielding gas composition of 95%Ar-5%CO2 exhibits good corrosion resistance over the other two welds while the weld made with the shielding gas composition of 60%Ar -40%, shows very poor corrosion resistance.

A comparative study between pulsed metal inert gas welding and continuous metal inert gas welding on thin Invar alloy

The pulsed metal inert gas welding and continuous metal inert gas welding with various parameters are implemented on 2-mm-thick Invar36 alloy plates. The pulsed metal inert gas welding and continuo...

3D measurement of temperature and metal vapor concentration in MIG arc plasma using a multidirectional spectroscopic method

Tweetable abstract3D measurement for MIG arc plasma was developed with 12 cameras equipped with 3 types of interference filters.Spectroscopic measurements for metal inert gas (MIG) arc plasma have been recently performed. The studies have reported that the central core of the MIG arc has low temperature owing to the high radiation loss of iron vapor. In these studies, it was assumed that the MIG arc phenomenon is axially symmetric because of the measurement method using Abel inversion. GMA welding, including MIG arc welding, is normally performed with a travel speed and most of the phenomena become axially asymmetric. Tomographic measurement is required to obtain the internal emission intensity distribution of axially asymmetric phenomena. This study reports on a multi-directional and heterochromatic measurement system that can capture such axially asymmetric plasma. The proposed system is composed of 12 CCD cameras with three types of narrowband interference filters (one Ar I line and two Fe I lines). Each line intensity distribution was obtained using an image reconstruction method. We converted the line intensities into plasma temperature and iron vapor concentration by using the relative intensity method, absolute sensitive calculation, and solving the Saha equation under the LTE assumption. We measured a pulsed MIG welding process and observed that the temperature of the central area of the MIG arc plasma was lower than the outer area, as shown in recent conventional studies. We found such temperature and iron vapor distributions were drawn backwards along the welding line, and the time variation of the iron vapor concentration corresponded to the current pulse shape. We achieved the 3D measurement of the MIG arc through error estimation and comparison with the previous 2D studies.