Effect of Welding Parameters on Dilution and Weld Bead Geometry in Cladding

The effect of pulsed gas metal arc welding （GMAW） variables on the dilution and weld bead geometry in cladding X65 pipeline steel with 316L stainless steel was studied. Using a full factorial method, a series of experiments were carried out to know the effect of wire feed rate, welding speed, distance between gas nozzle and plate, and the vertical angle of welding on dilution and weld bead geometry. The findings indicate that the dilution of weld metal and its dimension i.e. width, height and depth increase with the feed rate, but the contact angle of the bead decreases first and then increases. Meantime, welding speed has an opposite effect except for dilution. There is an interaction effect between welding parameters at the contact angle. The results also show forehand welding or decreasing electrode extension decrease the angle of contact. Finally, a mathematical model is contrived to highlight the relationship between welding variables with dilution and weld bead geometry.     

Predicting of bead undercut defects in high-speed gas metal arc welding (GMAW)

In the gas metal arc welding (GMAW) process, when the welding speed reaches a certain threshold, there will be an onset of weld bead undercut defects which limit the further increase of the welding speed. Establishing a mathematical model for high-speedGMAWto predict the tendency of bead undercuts is of great significance to prevent such defects. Under the action of various forces, the transferred metal from filler wire to the weld pool, and the geometry and dimension of the pool itself decide if the bead undercut occurs or not. The previous model simplified the pool shape too much. In this paper, based on the actual weld pool geometry and dimension calculated from a numerical model, a hydrostatic model for liquid metal surface is used to study the onset of bead undercut defects in the high-speed welding process and the effects of different welding parameters on the bead undercut tendency.     

Predicting of bead undercut defects in high-speed gas metal arc welding (GMAW)

In the gas metal arc welding (GMAW) process, when the welding speed reaches a certain threshold, there will be an onset of weld bead undercut defects which limit the further increase of the welding speed. Establishing a mathematical model for high-speed GMAW to predict the tendency of bead undercuts is of great significance to prevent such defects. Under the action of various forces, the transferred metal from filler wire to the weld pool, and the geometry and dimension of the pool itself decide if the bead undercut occurs or not. The previous model simplified the pool shape too much. In this paper, based on the actual weld pool geometry and dimension calculated from a numerical model, a hydrostatic model for liquid metal surface is used to study the onset of bead undercut defects in the high-speed welding process and the effects of different welding parameters on the bead undercut tendency.     

Effects of activating flux on the welded joint characteristics in gas metal arc welding

This paper presents the effect of each welding parameter on the weld bead geometry, and then sets out to determine the optimal process parameters using the Taguchi method to determine the parameters. Three kinds of oxides, Fe₂O₃, SiO₂, and MgCO₃, were used to investigate the effect of activating flux aided gas metal arc welding (GMAW) on weld bead geometry, angular distortion and mechanical properties in AISI 1020 carbon steel. During welding, a charge coupled device (CCD) camera system was used to observe and record images of the welding arc and analyze the relationship between penetration increase and arc profile. The experimental results showed that activating flux aided GMAW increased the weld area and penetration and tended to reduce the angular distortion of the weldment. The MgCO₃ flux produced the most noticeable effect. Furthermore, the welded joint presented better tensile strength and hardness.     

Study on welding process and prosperities of AA5754 Al-alloy welded by double pulsed gas metal arc welding

In this paper, the effect of double pulsed gas metal arc welding (DP-GMAW) on metal droplet transfer, weld pool profile, weld bead geometry and weld joint mechanical properties of Al alloy AA5754 are presented. A high speed camera was utilized to reveal the metal transfer behavior and weld pool profile. A self-developed electrical signal acquire system was adopted to record the current waveform during welding process. The results indicated that the metal transfer, weld pool profile and weld bead geometry in DP-GMAW significantly differ with P-GMAW. The microstructure showed that grain size of the weld bead decreased with increasing of thermal pulse frequency, and the eutectic precipitates Mg₂Si were homogeneously distributed at fusion zone. The mechanical properties of welded joints were improved.     

Investigating effects of resistance wire heating on AISI 1023 weldment characteristics during ASAW

In this article, effects of advanced submerged arc welding process parameters on weld bead geometry have been investigated. A novel water-cooled torch has been developed which allow a use of higher preheat current values for a continuous advanced submerged arc welding (ASAW) operation. Weld beads have been deposited on AISI 1023 steel plates by varying open circuit voltage, wire feed rate, welding speed, nozzle to plate distance, and preheat current as per central composite design. The relationships between welding parameters and weldment characteristics namely bead width, penetration, reinforcement, and dilution have been developed using multiple linear regression. The effects of individual process parameters and their interactions on response parameters were examined. Finally, single and multiobjective optimization of process parameters were performed using desirability approach and Jaya algorithm. The results reveal that a smaller bead width and lower dilution can be achieved with the developed torch by allowing the use of higher preheat current values.     

Mathematical Modeling of Metal Active Gas (MAG) Arc Welding

In the present paper. a numerical model for MAG (metal active gas) arc welding of thin plate has been developed. In MAG arc welding, the electrode wire is melted and supplied into the molten pool intermittently. Accordingly, it is assumed on the modeling that the thermal energy enters the base-plates through two following mechanisms, i.e., direct heating from arc plasma and "indirect" heating from the deposited metal. In the second part of the paper, MAG arc welding process is numerically-analyzed by using the model. and the calculated weld bead dimension and surface profile have been compared with the experimental MAG welds on steel plate. As the result. it is made clear that the model is capable of predicting the bead profile of thin-plate MAG arc welding, including weld bead with undercutting.     

Experimental Investigation of Wire Arrangements for Narrow-Gap Triple-Wire Gas Indirect Arc Welding

A new narrow-gap welding process is proposed by applying triple-wire gas indirect arc (TW-GIA). There are double power supplies and triple wires in this system. Power supplies are only connected between electrode wires and base materials are not linked to power supplies. Since there are different wire arrangements with TW-GIA, this article studies these wire arrangements and their effects on sidewall fusion for narrow-gap welding. Results show that different wire arrangements lead to variant arc behaviors and metal transfer, and consequently they lead to different situation of sidewall fusion. The heat to melt sidewalls is mainly from the indirect arc column and metal transfer with narrow-gap TW-GIA. When side wires deviate from the main wire to opposite directions, heat from arc columns and metal transfer can concentrate toward groove sidewalls. When the whole weld torch is lowered, heat from the indirect arc column and metal transfer increases at the weld bead root.     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.     

Manual metal arc weld modelling: Part 1 Effect of process parameters on dimensions of weld bead and heat-affected zone

Abstract

The properties of a weldment are determined largely by the size and distribution of microstructural regions within the weld metal and heat-affected zone (HAZ). It has been appreciated for some time that these properties may be controlled by adjusting the parameters of the welding process, although until recently this was done mainly qualitatively. Means of achieving more quantitative control are now beginning to be applied. In this paper measurements of the sizes of the weld bead and HAZ are presented for single manual metal arc weld beads. The process variables investigated were electrode type, gauge size, welding position, polarity, welding current, preheat, and welding velocity. Functional relationships between the process variables and the size of the weld bead and HAZ are determined. The generality of these relationships is examined by analysing measurements made previously on other materials. The results are discussed in terms of the theory of the welding process and, as shown in two accompanying papers, they can be used to develop models of multipass manual metal arc welding on which a practical welding procedure may be based.

MST/193a     

Effect of heat-input and cooling-time on bead characteristics in SAW

Load-carrying capacity of weld joints could be identified by its shape and size where weld bead geometry and shape relationship parameters are of utmost importance. Heat input and preheating temperature together can control the cooling time of weld, which in turn determines the weld microstructure and its mechanical properties. To control the shape and geometry of weld bead, it is necessary to understand its relationship with cooling time. In present work, preheating temperature is used as process variable along with heat input varying parameters for understanding their effects on weld bead geometry and shape relationship parameters using submerged arc welding process on high-strength low alloy pipeline steel. The experimental investigation was then analyzed by using the mathematical modeling in context with response surface methodology. The mathematical model predicts the influential dependency of cooling time on the preheating temperature than the other weld process parameters. The associated effects in relation to the process parameters have been discussed and analyzed in the present study.     

An outlook on comparison of hybrid welds of different root pass and filler pass of FCAW and GMAW with classical welds of similar root pass and filler pass

In the present study, gas metal arc welding and flux cored arc welding were applied on SA516 Gr70 carbon steel material. Two different hybrid passes were applied, wherein flux cored wire and solid wire were applied to root pass and filler pass one by one and vice versa. Besides, two more welds of similar electrode root pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative analysis was carried out in terms of macrostructure and microstructure examination, tensile testing, hardness variations, and impact testing for these classical welds and hybrid welds. The results reveal that, hybrid welds lead to better impact properties relative to classical welds. Maximum angular distortion of 2.66° was reported with classical weld of gas metal arc welding with solid wire root pass and same filler pass. The maximum impact toughness of 49 J/m³ was reported for flux cored root pass and solid wire filler pass at the weld zone. Maximum tensile strength of 596 MPa was reported for hybrid weld of solid root pass and flux cored filler pass. Microstructures are reported with the presence of different acicular ferrite and grain boundary ferrite. Maximum acicular ferrite of 61% was reported with classical weld of flux cored arc welding.     

A comparative study of multiple regression analysis and back propagation neural network approaches on plain carbon steel in submerged-arc welding

Weld bead plays an important role in determining the quality of welding particularly in high heat input processes. This research paper presents the development of multiple regression analysis (MRA) and artificial neural network (ANN) models to predict weld bead geometry and HAZ width in submerged arc welding process. Design of experiments is based on Taguchi’s L16 orthogonal array by varying wire feed rate, transverse speed and stick out to develop a multiple regression model, which has been checked for adequacy and significance. Also, ANN model was accomplished with the back propagation approach in MATLAB program to predict bead geometry and HAZ width. Finally, the results of two prediction models were compared and analyzed. It is found that the error related to the prediction of bead geometry and HAZ width is smaller in ANN than MRA.     

590 MPa级高强钢双面双弧立焊焊缝组织性能

为研究590 MPa级高强钢双面双弧工艺得到的焊接接头组织与性能的关系,采用钨极氩弧焊(TIG)与熔化极气体保护焊(MAG)方法获得成型良好的焊接接头,经过拉伸、冲击、弯曲试验及光学显微镜、扫描电镜、EBSD分析,对590 MPa级高强钢双面双弧立焊打底焊与盖面焊焊接接头的组织及性能进行了研究.结果表明:打底焊缝组织主要为贝氏体,盖面焊缝组织以贝氏体与针状铁素体为主;打底焊缝经历过一次热循环后组织得到一定程度的细化;打底焊缝硬度值与盖面焊缝相近,盖面焊缝热影响区最高硬度值高于打底焊缝热影响区最高硬度;2 mm坡口间隙性能较5 mm坡口间隙有较大提高,2 mm坡口间隙断口以韧窝断裂为主,5 mm坡口间隙断口以解理断裂为主.     

Hybridization of filler wire in multi-pass gas metal arc welding of SA516 Gr70 carbon steel

In the present investigation, multi-pass gas metal arc welding (GMAW) of SA516 Gr70 carbon steel was carried out by different filler wires such as solid, metal cored and flux cored, wherein, other process parameters were kept constant. The hybrid approach of multi-pass filler wires was applied to obtain three different welds. The root pass was filled by a solid wire for all three cases while the subsequent filler pass was applied through solid, flux-cored and metal cored filler wires, respectively. Metallographic, mechanical and metallurgical analyses such as macrograph study, optical microscopy, tensile testing and hardness variations were performed to address the quality of weld. The results revealed that defect-free sound welds were produced by the hybrid approach of different filler wires in multi-pass GMAW. Overall cost and time reduction can be achieved through hybrid filler welds, without affecting their mechanical strength. Angular distortion was reported minimum at hybrid weld of solid and metal cored filler wire. Maximum reinforcement with higher penetration was observed at weld of solid and metal cored filler wire. Impact toughness was reported higher in case of hybrid weld of solid and flux cored filler wire. Higher macro hardness was reported at weld of solid and flux cored filler wire.     

Effect of Thermal Frequency on AA6061 Aluminum Alloy Double Pulsed Gas Metal Arc Welding

The present investigation aims to contrast the effect of the commonly used thermal frequency on welding process suitability, weld profile, weld macrostructure, and weld hardness on AA6061 aluminum alloy double pulsed gas metal arc welding. Material manufacturing processes and welding parameters with thermal frequencies of 2, 3, and 4 Hz are described in detail. Three defect-free welds were successfully formed at these thermal frequencies. The results indicate the following: (1) thermal frequency has no effect on welding process suitability when the welding parameters are self-matching; and (2) at increased thermal frequency, weld ripple distance reduces, maximum penetration depth decreases, grain size of the fusion zone decreases, and fusion zone hardness increases.     

Hybrid laser/arc welding of thick high-strength steel in different configurations

In this investigation, hybrid laser/arc welding (HLAW) was employed to join 8-mm-thick high-strength quenched and tempered steel (HSQTS) plates in the butt-and T-joint configurations. The influences of welding parameters, such as laser power, welding speed, stand-off distance (SD) between the arc of gas metal arc welding, and the laser heat source on the weld quality and mechanical properties of joints, were studied to obtain non-porous and crack-free fully-penetrated welds. The weld microstructure, crosssection, and mechanical properties were evaluated by an optical microscope, and microhardness and tensile tests. In addition, a finite element model was developed to investigate the thermal history and molten pool geometry of the HLAW process to join the HSQTS. The numerical study demonstrated that the SD had a paramount role in good synergy between the heat sources and the stability of the keyhole. For the butt-joint configuration, the results showed that, at a higher welding speed (35 mm/s) and optimum SD between the arc and laser, a fully-penetrated sound weld could be achieved. A non-porous weld in the T-joint configuration was obtained at a lower welding speed (10 mm/s). Microstructural evaluations indicated that the formation of residual austenite and the continuous network of martensitic structure along the grain boundary through the heat affected zone were the primary reasons of the softening behavior of this area. This was confirmed by the sharp hardness reduction and failure behavior of the tensile coupons in this area.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-017-0193-6     

Comparative experimental study on the modification of microstructural and mechanical properties of friction stir welded and gas metal arc welded EN AW‐6061 O aluminum alloys by post‐weld heat treatment

In this paper, the effects of post‐weld heat treatment on modification of microstructures and mechanical properties of friction stir welded and gas metal arc welded AA6061‐O plates were compared with each other. Gas metal arc welding and friction stir welding were used as the applicable welding processes for AA6061‐O alloys. The applied post‐weld heat treatment consisted of solution heat treatment, followed by water quenching and finally artificial aging. The samples were classified as post‐weld heat treated and as‐welded joints. The microstructural evolution, tensile properties, hardness features and fracture surfaces of both as‐welded and post‐weld heat treated samples were reported. The results clearly showed that friction stir welding process demonstrated better and more consistent mechanical properties by comparison with the gas metal arc welding process. The weld region of as‐welded samples exhibited a higher hardness value of 80 HV0.1 compared to the base material. In addition, the feasibility of post‐weld heat treatment in order to enhance the mechanical properties and to obtain more homogeneous microstructure of 6061‐O aluminum alloys was evaluated.     

Hybrid laser/arc welding of advanced high strength steel in different butt joint configurations

An experimental procedure was developed to join thick advanced high strength steel plates by using the hybrid laser/arc welding (HLAW) process, for different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm from the weld centerline. The cross-section of the welds was examined by microhardness test. The microstructure of welds was investigated by scanning electron microscopy and an optical microscope for further analysis of the microstructure of fusion zone and heat affected zone. It was demonstrated that by changing the geometry of groove, and increasing the stand-off distance between the laser beam and the tip of wire in gas metal arc welding (GMAW) it is possible to reduce the width of the heat affected zone and softened area while the microhardness stays within the acceptable range. It was shown that double Y-groove shape can provide the optimum condition for the stability of arc and laser. The dimensional changes of the groove geometry provided substantial impact on the amount of heat input, causing the fluctuations in the hardness of the weld as a result of phase transformation and grain size. The on-line monitoring of HLAW of the advanced high strength steel indicated the arc and laser were stable during the welding process. It was shown that less plasma plume was formed in the case where the laser was leading the arc in the HLAW, causing higher stability of the molten pool in comparison to the case where the arc was leading.     

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.