Increasing Welding Current Research Articles

Study Of Parametric Effects On Mechanical Properties Of Stainless Steel (AISI 304) And Medium Carbon Steel (45C8) Welded Joint Using GMAW

Gas Metal Arc Welding (GMAW) is widely used for welding of carbon steel, silicon steel, low alloy steel, stainless steel, Al, Mg, Cu, Ni, Ti and their alloys. Welded surfaces produced are smooth, neat, clean and spatter free which require no further cleaning so reduces total welding cost. Because of the numerous applications of dissimilar metal welded joints, engineers and researchers are opting for dissimilar metal welding to create new structures or parts. Welding of dissimilar metals has more challenging task because the weld ability of dissimilar metals depends on many factors. It is difficult to join two different metals having different chemical, physical and metallurgical properties. A dissimilar metal weld zone contains a weld deposit with a chemical composition that differs by several percent from the composition of the two base metals that have been welded together. In the present study the aim is to weld stainless steel AISI 304 and medium carbon steel 45C8 using GMAW. Yield strength, ultimate tensile strength, weld zone hardness, weld bead thickness and reinforcement of the welded joint have been reported. The variables used are welding current, voltage, speed and gas flow rate. Taguchi’s Method has been employed for design of experiment. Based on ANOVA and S/N ratio analysis, the process parameter which significantly affects the responses is welding current. In the welded zone, the hardness decreases with increasing welding current. It has been observed that with the increase of welding current, weld bead thickness increases and reinforcement decreases. Microstructures of the base metals, both HAZs and weld zone have been investigated. Grain structure changes from base metal to HAZ and HAZ to welded zone. Grain size becomes more compact in welded zone.

Multifractal analysis for gas metal arc welding

The gas metal arc welding (GMAW) is a complicated chaotic dynamic process and its arc electrical signals have the characteristics of both chaos and fractals. The multifractal can accurately depict the geometric characteristics and local scale behaviors of time series signals. Through local and global self-similarity, we can determine the overall characteristics from the local dynamic behaviors of a dynamic system. Here, we used the multifractal theory to obtain the multifractal spectra under different welding parameters, and defined a multifractal spectrum index that described the multifractal spectrum of welding current signals. When the shielding gas flow increases under the short-circuiting mode, the welding process becomes more stable and the multifractal spectrum index decreases. As the welding current increases, the droplet mode gradually changes from the stable short-circuiting mode to the stable spray droplet mode, while the multifractal spectrum index first increases and then decreases. It is confirmed the droplet transfer behavior of GMAW is a complicated chaotic dynamic process, and the current signal has the multifractal characteristics. The multifractal spectrum distribution is closely related to the droplet transition mode and stability.

Prediction of Spot Welding Parameters for Dissimilar Weld Joints

Development of manufacturing systems are needed to invent new kind of methodology for joining process in current research and development. Spot welding technologies are widely applied in non-conventional joining process. In this investigation predicted the mechanical properties like tensile strength and Hardness. The hardness evaluated in different regions of the spot welded Stainless steel sheet and Mild steel sheet joints such as welded zone, heat affected zone and parent material subjected to different Welding Parameters. The Experimental procedures are developed by factorial design and the regression model developed from the experimental results through Response surface methodology. The variable parameters are Electrode force, Weld Current and the Weld time. The measurable parameters are Tensile strength and hardness. The optimization process is carried out by Response surface methodology and the optimized parameters are defined the quality of the welded steel joints. The optimized welded parameters are expressed the effective joining and improve the quality of the welded member. stainless steel .The phase transformation which occur during the weld thermal cycle were analyzed which shows that fusion zone exhibited a carbide precipitates with small amount of martensite the HTHAZ exhibited a martensite, the MTHAZ exhibiting the higher hardness, the LTHAZ exhibited Cr- carbide. The grain growth which occurred in FZ and HTHAZ is a major problem accompanied with fusion welding of FSSs. It shows that the peak load and energy absorption of the welds were improved as the welding current increases due to the formation of larger FZ size at higher heat input. (2) In their research, the effects of electrode force, weld nugget, and hardness of spot welded steel joints are examined based on observed values of the experiment. Mechanical properties and the microstructure of the welded joints are having significant impact on weld nudge. The significant values of difference are identified in the hardness due to the changes presence in weld nudge. The mechanical properties and the microstructure on the heat affected zone is preserve higher value compare with welded zone. (3) Weld nudges and weld time are investigated through Finite element methods by two dimensional models in resistant spot welding. This analysis defined the effect of nugget size and weld time on AISI304L stainless steel sheet.

Characteristics of welding and arc pressure in TIG narrow gap welding using novel magnetic arc oscillation

Tungsten inert gas (TIG) narrow gap welding using magnetic arc oscillation is one of the most important methods for joining thick components. Today’s developments are aimed at increasing a sophisticated process understanding, especially concerning the physical effect of arc behavior, which can provide many strategies to enhance weld prediction and joint quality. In this article, the arc behaviors studied by its arc pressure, static characteristic, and arc profile in terms of arc force are presented. With the help of the forces acting on the welding arc, arc profile can be considered separately to allow an improved investigation of narrow gap welding involved. Measurements of arc pressure distribution are used to validate the weld formation and the final welding result. Under the same conditions, the uniformity of arc pressure distribution in both the bottom and sidewall improved with the increase in magnetic flux density. Furthermore, a comparative study of arc static characteristic with magnetic field and non-magnetic field has also been carried out. The reduction in the difference of arc static characteristic is attributed to the inverse effect between electromagnetic pinch force and Lorentz force with the increasing welding current.

二段給電式ミグ溶接プロセスの数値シミュレーション

GMA welding under pure argon shielding gas atmosphere (pure argon-GMA welding) is suitable to obtain a high-strength and high toughness welded joint. However, it is difficult to apply pure argon-GMA welding practically to welding structure because of arc instability. In order to perform stable pure argon-GMA welding, duplex current feeding GMA welding has been developed. The duplex current feeding GMA welding consists of primary GMA welding current by constant-voltage power source and secondary current by constant-current power resource. In previous experimental study, it was found that the temperature of a droplet by duplex current feeding GMA welding was higher than the conventional GMA welding. In this study, mechanism and basic characteristics of duplex current feeding GMA welding are investigated by numerical simulation with a simplified duplex current feeding GMA welding model. As a result, it was found that total welding current was largely increased by conducting the secondary current in addition to the primary GMA welding current under the same arc voltage and wire feed speed. Furthermore, the droplet temperature was also increased due to the increase in total welding current.

Effect of Current on Characteristic for 316 Stainless Steel Welded Joint Including Microstructure and Mechanical Properties

Gas Metal Arc Welding (GMAW) process is a clean and cost effective process in arc welding which is higher productivity and good in quality. In this study, 316 stainless steel pipes with outside diameter is 73mm and 7.0mm thickness were joint using Tungsten Inert Gas (TIG) welding process. Various current settings were used to obtain the optimum joint characteristics and minimize defects that will contribute to cost effective. Mechanical characteristics of the welded alloys were carried out is tensile tests and hardness (HV). Metallographic examination was conducted to identify and observe the various fusion zones. Results show that the increase of welding current bring about the large amount of heat input in the welding pool, the enlargement of width and deepness of the welding pool, cumulative sigma phase in the matrix and reducing the chromium carbide percentage in 316 stainless steel welded joint. Arc current of 100A has been identified of the most suitable current since it gives the lowest defects and brings the highest value of strength and hardness for this material.

The mechanical properties of dissimilar resistance spot-welded DP600–DP1000 steel joints for automotive applications

A study was conducted to investigate the microstructure and the mechanical properties of dissimilar resistance spot welds between steel sheets of DP600 and DP1000 using different welding currents for automotive applications. Microstructural characterization, microhardness tests and tensile shear tests of the joints were conducted. The dissimilar joints had three main microstructural zones: the base metals; the heat-affected zones of both steels; the fusion zone. Additionally, the DP1000 side of the joints also had a transition zone between the heat-affected zone and the base metal, which exhibited significant softening. Such a soft transition zone was not observed on the DP600 side. The peak hardness values were observed in the centre heat-affected zones of both sides of the joints. The welding current significantly influenced the microstructure and the mechanical properties of the joints. With increasing welding current, the nugget size increased almost linearly and the widths of the heat-affected zones on both sides became smaller. The use of higher welding currents reduced the microhardness values in the outer heat-affected zones of both sides and the fusion zone of the joints; the hardness values in these zones decreased almost linearly with increasing welding current. For a welding current of up to 10 kA, the tensile shear loads of the joints increased linearly with increasing welding current. The peak values of the tensile shear load and tensile deformation were obtained for the joints welded with a current of 10 kA. All joints exhibited the full button pull-out failure mode under the tensile shear loading test. The failure location of all joints was in the centre heat-affected zone. The joints welded with relatively lower welding currents (8–9.5 kA) failed on the DP1000 side, while the failure of the other joints fabricated with relatively higher welding currents (10–11 kA) was located on the DP600 side of the weld.

The Behaviour of Nitrogen on the Welding Parameters of the Dissimilar Weld Joints between AISI 304 and AISI 316L Austenitic Stainless Steels Produced by Gas Tungsten Arc Welding

The behavior of nitrogen into the dissimilar joining metal between AISI 304 and AISI 316L Austenitic stainless steel during gas tungsten are welding process was investigated. Studied by using an arc nitrogen atmosphere – controlling in chamber. The relations between nitrogen content of the dissimilar weld metal and the welding parameters, such as the welding current, welding speed, welding arc length and penetration area of weld metals were also evaluated. The results show that the nitrogen content of the weld metals decreased with an increasing welding current, and increasing penetration areas of weld metal, but scarcely depends on the welding arc length. The nitrogen content of the weld metals increased with the welding speed, but decreased penetration areas of weld metals. The role of nitrogen content on the dissimilar weld metals stainless steel is further confirmed by the experimental microstructure, mechanical and corrosion behaviour of the weld metal.

Mass Transfer of Nickel-Base Alloy Covered Electrode During Shielded Metal Arc Welding

The mass transfer in shielded metal arc welding of a group of nickel-base alloy covered electrodes according to AWS specification A5.11-A5.11M was investigated by directly measuring their deposited metal compositions. The results indicate that the chromium mass-transfer coefficient is in the range of 86 to 94 pct, iron in the range of 82 to 89 pct, manganese in the range of 60 to 73 pct, niobium in the range of 44 to 56 pct, and silicon in the range of 41 to 47 pct. The metal mass-transfer coefficient from the core wire is markedly higher than that from the coating. The basicity of slag, the metal contents in the flux coating, and the welding current together affect the mass transfer. As the basicity of slag increases, the mass-transfer coefficients of Mn, Fe, and Cr slightly increase, but those of Nb and Si decrease significantly. As the niobium and manganese contents increase in the coating, their mass-transfer coefficients also increase. However, iron is different. The content of iron in the coating in the range of 8 to 20 wt pct results in the optimal effective mass transfer. The lower, or higher, iron content leads to lower mass-transfer coefficient. As the welding current increases, the mass-transfer coefficients of niobium and manganese decrease, but chromium and silicon increase. Iron has the lowest mass-transfer coefficient when welded under the operating current of 100 A.

On failure mode of resistance spot welded DP980 advanced high strength steel

This paper aims at investigating the correlation between metallurgical and mechanical characteristics of DP980 dual phase steel resistance spot welds with attention focused on the transition in failure mode from interfacial to pullout mode during the tensile shear test. It was studied whether the conventional/industrial weld size criteria can produce pullout failure modes for DP980 spot welds. Based on theoretical analysis and experimental results, there is a minimum fusion zone size which beyond that the interfacial failure mode is avoided. Results showed that by increasing welding current, pullout failure mode was promoted due to increasing the fusion zone size and encouraging martensite tempering in subcritical heat affected zone (HAZ). Fusion zone size was proved to be key factor controlling mechanical properties of DP980 welds in terms of peak load, ductility and failure energy.Ce document vise à examiner la corrélation entre les caractéristiques métallurgiques et mécaniques de soudures par points par résistance de l’acier biphasé DP980, en mettant l’accent sur la transition du mode de défaillance de mode d’interface à mode par arrachement lors de l’essai de traction-cisaillement. On voulait savoir si les critères conventionnels ou industriels de taille de la soudure pouvaient produire des modes de défaillance par arrachement des soudures par points de DP980. L’analyse théorique et les résultats expérimentaux indiquent qu’il y a une taille minimale de la zone de fusion au-delà de laquelle on évite le mode de défaillance d’interface. Les résultats ont montré qu’en augmentant le courant de soudage, le mode de défaillance par arrachement était favorisé, à cause de l’augmentation de la taille de la zone de fusion et de l’encouragement du revenu de la martensite dans la HAZ sous critique. On a démontré que la taille de la zone de fusion constituait une composante clé contrôlant les propriétés mécaniques des soudures de DP980 en ce qui a trait à la charge de pointe, à la ductilité et à l’énergie de défaillance.

Effect of submerged arc welding parameters on microstructure of SA516 steel weld metal

The influence of submerged arc welding (SAW) process parameters on the microstructure of SA516 grade 70 steel weld metal (WM) was investigated in the present work. Steel plates of 17 mm thickness were submerged arc welded using welding currents of 700–850 A and welding speeds of 5·3–15·3 mm s−1. The morphologies and volume fractions of the various ferrites in the WM were studied using optical microscopy and the morphologies and chemical compositions of the WM inclusions were examined using scanning electron microscopy and energy dispersive X-ray spectrometry. The results showed that the WM grain structure coarsened but the grain width of prior austenite grains decreased with increasing heat input. Also, the proportion of acicular ferrite (AF) in the WM increased initially, while the volume fractions of grain boundary ferrite and Widmanstätten ferrite decreased with increasing welding current. However, with further increasing the welding current above 800 A, less AF was produced. The weld nugget area decreased with increasing welding speed at all currents, but did not affect the amount of AF produced.Au cours de ce travail, on a examiné l’influence des paramètres du procédé de soudage à l’arc sous flux en poudre (SAW) sur la microstructure du métal soudé (WM) de l’acier SA516, Gr. 70. On a soudé à l’arc sous flux en poudre des tôles d’acier de 17 mm d’épaisseur en utilisant des courants de soudage de 700 à 850 A et des vitesses de soudage de 5·3 à 15·3 mm s−1. On a étudié la morphologie ainsi que la fraction volumique des diverses ferrites du WM en utilisant la microscopie optique et l’on a examiné la morphologie ainsi que la composition chimique des inclusions du WM en utilisant la microscopie électronique à balayage (SEM) et la spectroscopie à dispersion d’énergie (EDS). Les résultats ont montré que la structure de grain du WM grossissait mais que la largeur de grain des grains antérieurs d’austénite diminuait avec une augmentation de l’apport de chaleur. Également, la proportion de ferrite aciculaire (AF) dans le WM augmentait initialement, alors que les fractions volumiques de ferrite des joints de grain (GBF) et de ferrite de Widmanstatten (WF) diminuaient avec l’augmentation du courant de soudage. Cependant, avec une augmentation supplémentaire du courant de soudage au-dessus de 800 A, moins de ferrite aciculaire était produite. La région du noyau de soudure diminuait avec une augmentation de la vitesse de soudage à toutes les valeurs de courant, mais la quantité d’AF produite n’était pas affectée.

Investigations on the Influence of Surfacing Process Parameters Over Bead Properties During Stainless Steel Cladding

The bead parameters play a vital role in determining and understanding the properties of the weld cladding in fusion welding process. This investigation aims at minimizing weld dilution and predicting the behavior of the bead parameters during weld cladding of AISI 316 L (UNS 316 03) metal powder over carbon steel (ASTM A105/ IS: 2062), by plasma transferred arc (PTA) surfacing through response surface method. The data for modeling were collected from experiments conducted using a five level factorial technique. The predictions reveal that the travel speed has a phenomenal effect in increasing the penetration of the weld bead at lower level. The torch stand-off distance has a predominant effect in deciding the penetration and dilution of the weld bead during lower level while increasing welding current. The reinforcement of the weld bead reduced the dilution level with increase in the oscillation frequency and the powder feed rate.

Study on Intermediate Frequency Spot Welding Process of Hot Stamping High Strength Steel

The joints of RSW for HSHSS were prepared with IF spot weld equipment. The weld nugget, fracture mode, microstructure and micro-hardness of the joints were investigated. The weld nugget increases and the fracture mode changes from interfacial fracture to nugget plug fracture with the increasing welding current. There are three distinct zones in the weld joint: weld nugget, heat affected zone (HAZ) and base metal. The microstructure of HAZ includes tempered zone (HAZ-1), incomplete quenching zone (HAZ-2) and complete quenching zone (HAZ-3). The micro-hardness of weld nugget and HAZ-3 is same with the base metal. The micro-hardness of HAZ-1 and HAZ-2 is smaller than that of base metal.

Effects of Welding Parameters on Microstructure and Mechanical Properties of the Joint of the Magnesium Alloy AZ31B

Through the metal inert gas welding (MIG) experiment, the effects of the different welding parameters on the microstructure, the weld configuration and the mechanical properties of the joint of the magnesium (Mg) alloy AZ31B were analyzed. The results indicate that with the increase in the welding current, the microstructure change of the weld is characterized by the grain coarsening, and the microstructure change of the heat affected zone is characterized by the grain coarsening and the broadening of the heat affected zone. An exorbitant welding current is inimical to the weld configuration. With the increase in the welding speed, the welding linear energy decreases, inducing the formation of the finer equiaxed grains in the weld. Moreover, the grains in the heat affected zone are also with the trend of the refinement, and thus the mechanical properties of the joint increase. The optimal welding current and speed in our experiment are 160-170A and 400-450mm/min, respectively.

Investigation on Joint Strength of Dissimilar Resistance Spot Welds of Aluminum Alloy and Low Carbon Steel

Resistance spot welding was used to join low carbon steel and A5250 Aluminum alloy sheets. Mechanical properties and failure behavior of the spot welds in terms of peak load, failure energy and failure mode, were evaluated using tensile- shear test. Relationship between welding current and mechanical properties was investigated. It was found that the formation of brittle intermetallic compounds in the weld fusion zone is the key governing factor for mechanical properties of dissimilar Al alloy/low carbon steel resistance spot weld. Increasing welding current, increases both peak load and energy absorption due to increasing overall bond area and transition in failure mode from interfacial to pullout failure mode.

Effect of welding parameters on residual stresses in dissimilar joint of stainless steel to carbon steel

In this study, a thermo-mechanical model was utilized to investigate the effects of welding parameters on the distribution of residual stresses in dissimilar TIG welds of low carbon and ferritic stainless steels. To solve the governing thermal and mechanical problems, a finite element program, ANSYS, was employed while the different aspects such as welding sequence and dilution were considered in the numerical solution. To validate the predictions, the model results were compared with the residual stresses measured by X-ray diffraction technique and a reasonable agreement was found. The results show that the magnitude of tensile residual stresses decrease as the welding current increases while lower residual stresses are produced in the longer samples. In addition, the magnitudes of residual stresses significantly decrease when a symmetric welding sequence is employed especially for the carbon steel part with the higher yield strength.

Análise comparativa da geração de fumos entre arames maciços (GMAW) e tubulares (FCAW)

O processo GMAW (MIG/MAG) é muito utilizado no meio industrial. Entretanto, este processo apresenta limitações quanto a ações metalúrgicas sobre a zona fundida e moldabilidde do cordão. O processo FCAW, por outro lado, por apresentar elementos fluxantes, consegue melhores resultados nestes aspectos, mas o fluxo pode ser um agente responsável por elevada emissão de fumos. Este trabalho teve por objetivo apresentar um estudo comparativo da geração de fumos entre o processo GMAW com transferência metálica por curto-circuito e o processo FCAW sob proteção gasosa, ambos com eletrodos de mesma classe de resistência mecânica (483 MPa de limite de ruptura) e aplicação. Os experimentos foram realizados utilizando-se um coletor de fumos calibrado de acordo com norma. Os dois consumíveis foram avaliados sob uma proteção de 100% CO2 em dois níveis de corrente. O efeito do comprimento do arco e do uso de outra proteção (Ar+25% CO2) também foi avaliado. Para se possibilitar uma comparação próxima da realidade prática de cada consumível, procurou-se trabalhar com cada combinação arame/gás de proteção em condições apropriadas de distância bico de contato-peça e de regulagem de tensão. Fixou-se ainda o mesmo volume do cordão de solda por metro para cada nível de corrente, mantendo-se constante a relação entre a taxa de deposição e a velocidade de soldagem. Os resultados confirmam uma maior taxa de geração de fumos pelo processo FCAW (já esperado) e que a taxa absoluta de fumos cresce com o aumento da corrente de soldagem, porém para processo GMAW analisado de forma relativa (em função da massa fundida) isso não ocorre. Verificou-se que o efeito da corrente é mais significativo para o processo FCAW. O aumento do teor de CO2 elevou a taxa de geração de fumos apenas no processo FCAW, enquanto que a variação da tensão de arco não demonstrou qualquer efeito sobre esta.

Resistance Spot Welding Characteristics and Mechanical Properties of Galvannealed HSLA 350 Steel

Galvannealed high strength low alloy steel 350 (GA HSLA 350), because of its high strength-to-weight ratio, is particularly attractive in transportation applications. The GA HSLA 350 steel was spot welded at different welding currents to identify a suitable welding current giving good spot welds. Failure loads in the tensile shear increased with increasing welding current. There was a concomitant increase in the nugget diameter and the failure mode changed from interfacial fracture to button pull-out failure. Cross tension and microhardness tests were also carried out. The fusion zone microstructure was martensitic with a microhardness that was twice that of the base metal.

Numerical simulation for welding pool and welding arc with variable active element and welding parameters

A numerical modelling of the welding arc and weld pool is established for moving argon shielded gas tungsten arc welding to systematically investigate the effect of the active element oxygen and the welding parameters on the Marangoni convection and the weld shape using FLUENT software. The different welding parameters will change the temperature distribution and gradient on the pool surface, and affect the strength of Marangoni convection and the weld shape. Under high oxygen content, the weld depth/width (D/W) ratio substantially depends on the welding parameters. A high welding speed or large electrode gap (arc length) will make the weld D/W ratio decrease. The weld D/W ratio initially increases and then remains constant around 0·5 with the increasing welding current. When the oxygen content is lower, the weld D/W ratio decreases with the increasing welding current. However, the weld D/W ratio is not sensitive to the welding speed or electrode gap. The predicted weld D/W ratio agrees well with the experimental results.

NUMERICAL STUDY FOR GTA WELD SHAPE VARIATION BY COUPLING WELDING ARC AND WELD POOL

A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.