Pulsed Metal Inert Gas Welding Research Articles

Microstructure and properties of AL-SI alloy cladding on AZ91D magnesium alloy by low heat input DC-PMIG welding

The corrosion resistance of magnesium is an important research field for useful application in industry. In order to form a corrosion resistant layer with enough thickness and strong adhesion on the surface of magnesium alloy, a low cost and efficient production process–direct current (DC) pulse metal inert gas (PMIG) welding was used to deposit Al-Si alloy on AZ91D magnesium matrix. The heat input was strictly controlled to form compact metallurgical coating with a maximum thickness of 1.8mm. The composite layer can be divided clearly into three zones: Mg matrix zone, the transition zone composed of a variety of intermetallic compounds (Al12Mg17, Al3Mg2 and Mg2Si etc.), and alloy coating (α-Al dendrites, Al-Si eutectic and Mg2Si.) zone. Furthermore, the properties of the alloy coating zone were investigated by both micro-hardness test and electrochemical corrosion. The micro-hardness of the coating is almost two times higher than that of the matrix and the corrosion resistance of the coating was greatly improved compared with that of the matrix.

Effect of process parameters on ferrite number in cladding of 317L stainless steel by pulsed MIG welding

In the current scenario cladding process are used in many engineering industries to enhance the corrosion resistance surface and wear resistance of the base material in chloride environment. Cladding of stainless steel results in formation of ferrite number content on cladded surface, which deleterious the material properties. The present investigation address the effect of process parameters on ferrite number during austenitic stainless steel 317L cladding by Pulsed Metal inert gas (MIG) welding process. Ferrite number was measured by using Fisher’s ferrite scope. Response surface methodology (RSM) based central composite rotatable design were approached to predict and develop the mathematical model for process parameters such as welding current, welding speed and contact tip to work distance on ferrite number. From the analysis of variance technique it is found that the developed mathematical model was significant. The developed mathematical model is useful to control and determine the ferrite number content in austenitic stainless steel cladding. The direct and interaction effects of input process parameters are presented graphically.

Real-time monitoring of welding path in pulse metal-inert gas robotic welding using a dual-microphone array

Online monitoring of welding path is important as deviation from the welding path will significantly affect the welding quality. This paper proposed a welding path monitoring system using a dual-microphone array for the pulse metal-inert gas (MIG) robotic welding process. A calibration method was developed for microphones to find best locations for collectin arc sound signals. Arc sound features were analyzed to obtain the relationship between the arc sound signal and the welding path deviation. Prediction models for welding paths were then established in two ways: (1) the prediction model was based on individual microphone signals and (2) the model was based on signals from the dual-microphone array which proved to have better prediction accuracy in monitoring the welding path. The dual-microphone model showed its potential advantage in quality monitoring and control for the MIG welding process. The prediction error could reach 0.6708 and 1.1901 mm. The monitoring system based on a dual-microphone array could meet the position accuracy requirement of welding quality control in pulse MIG welding.

Studies on Mechanical Properties, Fracture Morphology and Corrosion Behavior of Pulsed MIG Welded AZ31B Magnesium Alloy Sheets

AZ31B Magnesium alloy plates were successfully joined by using alternating current pulsed Metal inert gas welding (AC p-MIGW) with AZ61 Magnesium alloy wire as the filler metal. The macrostructure, tensile strength, micro hardness and corrosion rate of welded magnesium alloy joints were studied. Results showed that magnesium alloy plates could be successfully joined by pulsed MIG welding under specified process parameters. The average tensile strength of the joint was 81.34 N/mm2. The micro hardness was averagely about 67.62 HV. The joint was brittle fractured in the middle of weld zone. The corrosion rate of the welded joint was found to be 0.0112 mm/year.

Sensitivity Analysis for Process Parameters in Cladding of Austenitic Stainless Steel by Pulsed Metal Inert Gas Welding Process

In recent scenario, the automation in weld cladding process has a challenging task for most of the industries like automotive, petrochemical and food processing industries. Because to achieve the best quality of the weld clad bead geometry during automated process it is important to have complete control over the selected process parameters. The cladding process enhances the base material properties. Therefore, it is essential to predict the relationship between the process parameters and response the second order polynomial regression equation has to be developed. It makes more effectiveness of automated weld cladding processes. Palani and Murugan [1] developed a mathematical model for a flux cored arc welding process using an RSM method to study the direct effects and interaction effects of process parameters on clad bead geometry.

Study on the transient impact energy of metal droplet transfer in P-MIG welding based on acoustic emission signals analysis

According to the structure-borne acoustic emission (AE) signals detected in pulsed metal inert gas (P-MIG) welding on aluminum alloy, the energy gradient and total energy of AE signals were used to describe the rate of impact energy and total impact energy coming from metal droplet transferred into molten pool. The results showed that there were three types of energy gradient curves according to three modes of metal droplet transfer (MDT). The characteristics of energy gradient curves had a close relation to the transient impact energy of MDT. The energy gradient of MDT decreased with the rise of pulse frequency during the impact process of not only one metal droplet but also several metal droplets within 0.04s. So, the variation rate of impact energy was lowered with the raise of transfer frequency on the premise of one droplet per pulse mode. Total energy of AE signals coming from not only one metal droplet but also several metal droplets within 0.04s also demonstrated a downward trend. On the premise of one droplet per pulse mode, the variation of the transient impact energy accorded with an exponential attenuation model.

Effect of torch position and angle on welding quality and welding process stability in Pulse on Pulse MIG welding–brazing of aluminum alloy to stainless steel

In this paper, Pulse on Pulse metal inert gas (MIG) welding–brazing of 6061 aluminum alloy to 304 stainless steel in a lap configuration was developed to investigate the effect of torch position and angle on the welding quality and welding process stability. Images of arc, electrical signals of welding current, and welding voltage were acquired in synchronous modes by a high-speed camera and electrical signal acquisition system, respectively. The obtained results demonstrate that arc shape, macrostructure, microstructure, and mechanical properties are sensitive to torch aiming position when torch travel angle is 20° and work angle is 0°. However, when travel angle is 20° and work angle is 20°, the effect of torch aiming position is insignificant. It is easier to strike arc and maintain it on the surface of aluminum alloy compared to stainless steel. High-strength joints, whose fracture occurred at heat-affected zones of Al alloys at 89 MPa up to 72 % of the tensile strength of Al alloys, have been obtained. Moreover, a comprehensive evaluation method for the welding process stability based on statistical techniques has been proposed. This method can be easily and quickly integrated in real-time control of the welding process, which provides a quantitative guidance in MIG welding–brazing of aluminum alloy to stainless steel.

Correlation between stability of aluminium alloy pulsed metal-inert gas welding and pulse current signal

In order to evaluate the stability of the process of aluminium alloy pulsed metal-inert gas welding, pulse current signals are analysed under different conditions of stability based on modern digital signal processing methods such as approximate entropy and probability density. Then correlation between the stability of aluminium alloy pulsed metal-inert gas welding and pulse current signals is observed, and the characteristic value S, which controls the stability of welding process, is quickly obtained (within 25 ms). Thus, S can be used as the feedback criteria of real-time control in the process of aluminium alloy pulsed metal-inert gas welding.

Sensor based prediction of weld microstructure in pulsed MIG welding

Pulsed gas metal arc welding (P-GMAW) is often used to improve weld quality as well as productivity in today's manufacturing industries. Current pulsing is used in grain refinement of weld fusion zone and uniform microstructure with less heat input. In this work, weld microstructure and its hardness have been studied on low carbon steel in pulsed metal inert gas welding using bead on plate method. The primary objective was to compare the grain morphology and different phase percentage to hardness variation in various welding zones, especially in the interface of weld fusion zone and heat affected zone (HAZ), affected by pulse parameters. Various sensors have been used to monitor the weld microstructural features. The weld peak temperature along with arc heat input were found to be strongly correlated with weld ferrite content, grain size and its hardness. The arc sound is also an essential indicator of weld microstructure affected by arc stability.

Modeling and Control of Pulsed Double-electrode MIG Welding Process

Pulsed double-electrode metal inert gas welding is a new kind of low heat input welding method. With different connection, parts of welding current bypassed and it controlled the base metal current and melting current separately. With free-flight metal transfer process, it could weld dissimilar metals. Aiming at the unstability of coupling arc in pulsed double-electrode metal inert gas welding process, a dynamic mathematic model has been built to truly describe and simulate the welding process with equivalent simplification, linearization and iterative solution. Then a control scheme is put forward and simulated, which changes the wire feed speed to adjust the main arc length, and further to control the stability of the coupling arc. Also the welding experiments with control scheme are carried based rapid prototyping system. Simulations proved the effectiveness of control scheme. And with controlling, the welding experiment is more stable and a good Al-Fe joint is acquired.

Study and Investigations on Process Parameters for Bead Geometry during Cladding by Pulsed MIG Welding Process

Bead geometry is a very important factor in achieving and studying the properties of the weld cladding in fusion welding process. This paper addresses minimization of depth of penetration and predicting the behavior of the cladded bead parameters during cladding of AISI 317L stainless steel electrode of 1.2mm diameter over low carbon structural steel (ASTM A105/ IS: 2062), by using Pulsed Metal Inert Gas welding process through response surface methodology. The input process parameters for present analysis are welding current (I), welding speed (S) and nozzle-to-plate distance (N) respectively. Experiments were conducted as per central composite design techniques, models were developed from the collection of data, and the measured responses are viz., depth of penetration, height of reinforcement and bead width. From the ANOVA it was found that welding speed and nozzle-to-plate distance is the dominant parameter in deciding the depth of penetration of the weld bead at the lower level. It is also found that the height of reinforcement reduces with increase in the welding speed.

Development of Mathematical Model for Prediction of Convexity Index in Cladding by Pulsed MIG Welding Process

Pulsed metal inert gas welding (PMIGW) process is more effective for cladding. The input process parameters for present analysis are welding current (I), welding speed (S) and nozzle-to-plate distance (N) respectively. By using response surface methodology technique the experiments were conducted as per central composite design techniques. The measured response is convexity index and models were developed from the collection of data and checked for their adequacy. Analysis of variances was used to analysis the input process parameters. The direct effect and interactive effect of the process parameters on the convexity index is significant and cannot be neglected it is represented graphically.

Study on DC Double Pulse Metal Inert Gas (MIG) Welding of Magnesium Alloy

This article gives a preliminary research on direct current (DC) double pulse metal inert gas (MIG) welding of magnesium alloys. It will be an effort for broadening the application of this new MIG welding process. The unique parameters of DC double pulse MIG welding are selected to investigate their effects on weld bead geometry size and appearance of AZ31B Mg alloy, and the principles of their effects are summarized. Then, butt joints are produced with optimum and stationary parameters by using the new process, and high quality surfaces without spattering, undercut, or discontinuous beads are obtained. For verifying the reliability of this new process on welding of Mg alloy, microstructure, mechanical property, and fracture characteristics of the butt joint are analyzed in detail. Results show the joint has fine homogenous microstructure and high ultimate tensile strength, which is up to 96% of that of the base metal. The fracture surfaces of the butt joints and base metal show a mixed fracture characteristic with tearing cleavage planes and deformed dimples.

Study on Arc Length Stability of Pulsed MIG Welding Based on Average Output Characteristics of Pulse Cycle

Average output characteristics curve is proposed by calculate rate of changes of average arc current and average arc voltage for pulsed metal inert gas(MIG) welding in a period of pulse.In addition,arc operating points of dynamic stability are analyzed for intersection of average output characteristics curve of a pulse cycle for arc welding power and arc static characteristics curve.A control strategy is obtained for pulsed MIG welding using average output characteristics in a pulse cycle.At the same time,digital arc welding power source of I/I mode control based on arc voltage feedback is realized by using double-loop control.Arc welding power adapts to change of arc length perturbation in the case of wire-feed speed stability.Droplet transfer of one-drop per pulse has achieved in pulsed arc welding process.Finally,through arc length step test shows that wire melting rate tracked arc length change immediately,there is a good dynamic performance adjustment and maintain dynamic stability for arc length.This is concluded that pulsed welding process is stable,weld appearance is beautiful.It is verified that the analysis process is correct and the design process is feasibly by experiment.

Multi-sensor based prediction of metal deposition in pulsed gas metal arc welding using various soft computing models

The deposition efficiency is an important economic factor in welding. A multitude of uncontrollable factors influence the metal deposition, which indicates the necessity of robust sensors with an intelligent system to monitor the process in real time. This paper attempts to develop artificial neural network (ANN) models to predict the weld deposition efficiency using the welding sound signal along with the welding current and the arc voltage signals in pulsed metal inert gas welding. Three different implementations of ANNs have been used: gradient descent error back-propagation, neuro-genetic algorithm and neuro-differential evolution. The results indicate that the sound signal kurtosis, used in conjunction with the current and the voltage signals, is a reliable indicator of deposition efficiency.

Study on DC Double Pulse MIG Welding of Automobile Aluminum Alloy

In this paper, the features of weld formation, porosity, arc behavior, microstructure and mechanical properties of 6061 Al alloy thin sheet welds by direct current (DC) double pulse metal inert gas (MIG) welding process are investigated and compared with the traditional DC MIG welding process. Results show that continuous one-side welding with back forming weld beads without spatters, undercuts or cracks can be obtained by using the DC double pulse MIG welding process. The porosity of weld bead can be largely reduced by using the process. The arc of DC double pulse MIG welding is stable without arc blowout, and the metal transfer model of DC double pulse MIG welding is better than that of DC MIG welding. Microstructure of the weld bead by DC double pulse MIG welding shows a dendrite structure and it is fine and uniform. The average ultimate tensile strength and elongation of the weld bead by DC double pulse MIG welding can get to 228MPa, 80% of base metal, and 7.6%, 63% of base metal.

Monitoring of Weld Penetration Using Arc Acoustics

The weld penetration monitoring is a challenging work in modern automated manufacturing industries. The weld quality can be improved with higher depth of penetration and less weld pool area. In this work, various pulse parameters have been varied to investigate their influence on weld penetration in pulsed metal inert gas (P-MIG) welding. The primary objective was to improve the depth of penetration adjusting the pulse parameters. The sound sensor and an infrared pyrometer were used along with arc sensors to properly monitor the depth of weld penetration. Finally, an attempt has also been made to correlate the time domain statistical features of each sensor with weld bead characteristics.

Optimisation of weld deposition efficiency in pulsed MIG welding using hybrid neuro-based techniques

The weld quality depends primarily on the degree of arc stability and the bead characteristics in gas metal arc welding. The weld deposition has to be enhanced to make the process economically feasible. This article addresses modelling and optimisation of deposition efficiency in highly non-linear pulsed metal inert gas welding. The design of experiments was performed using central composite response surface methodology for the model development. The back propagation neural network technique was found to be better than the response surface regression model. Two global optimisation techniques, namely, genetic algorithm and differential evolution, were then applied to maximise the deposition efficiency. The capability to identify the hidden optimum solutions using differential evolution technique was found to be better than genetic algorithm.

Pulsed MIG welding of AZ31B magnesium alloy

Pulsed metal inert gas welding of AZ31B magnesium alloy is carried out, and continuous butt joints of high quality are obtained at optimised parameters. The effects of parameters on weld formation and welding stability are studied. The microstructure, mechanical properties and fracture of weld beads with different filler wires are investigated. The results show that it is a stable drop transition process with optimised parameters, which belongs to globular transfer. The precipitates in fusion zone and heat affected zone (HAZ) are uniform, dispersive and almost granular. The grain size in fusion zone is fine, and the grain size does not grow too large in HAZ compared with the base metal. The ultimate tensile strength of weld beads can be 94% of base metal, and the average elongation is 11%. Dimples and coarse tearing ridges can be observed on the fracture of the weld bead.

Determination of Optimal Pulse Metal Inert Gas Welding Parameters with a Neuro-GA Technique

Optimization of a manufacturing process is a rigorous task because it has to take into account all the factors that influence the product quality and productivity. Welding is a multi-variable process, which is influenced by a lot of process uncertainties. Therefore, the optimization of welding process parameters is considerably complex. Advancement in computational methods, evolutionary algorithms, and multiobjective optimization methods create ever-more effective solutions to this problem. This work concerns the selection of optimal parameters setting of pulsed metal inert gas welding (PMIGW) process for any desired output parameters setting. Six process parameters, namely pulse voltage, background voltage, pulse frequency, pulse duty factor, wire feed rate and table feed rate were used as input variables, and the strength of the welded plate, weld bead geometry, transverse shrinkage, angular distortion and deposition efficiency were considered as the output variables. Artificial neural network (ANN) models were used for mapping input and output parameters. Neuro genetic algorithm (Neuro-GA) technique was used to determine the optimal PMIGW process parameters. Experimental result shows that the designed parameter setting of PMIGW process, which was obtained from Neuro-GA optimization, indeed produced the desired weld-quality.