Wire Feed Research Articles

Single-pass high-power laser-Arc hybrid welding of thick stainless steel clad plates: Microstructure and mechanical properties

In order to solve the existing problem of low efficiency of multi-layer and multi-pass welding methods for thick stainless steel clad plate (SSCP), this paper proposes high-power laser-arc hybrid welding (HP-LAHW) single-pass weld thick SSCP. The effects of wire feeding rate (WFR) on the weld's composition distribution, microstructure and mechanical properties were investigated. The weld morphology is nail-shaped, consisting of a wide arc zone (ArcZ) within the stainless steel layer and a long narrow laser zone (LaserZ), mainly in the carbon steel layer. With the increase of WFR, the dilution rate of the carbon steel layer to the ArcZ decreases first and then increases. The influence of WFR on the microstructure and mechanical properties of the weld is observed mainly in the ArcZ. When the WFR reaches 6 m/min, the composition of the microstructure within the ArcZ will change from martensite, ferrite, and a small amount of granular austenite to ferrite and a small amount of austenite, resulting in the microhardness of the ArcZ decreasing rapidly from 398 HV to 210 HV. The solidification type and microstructure transformation mechanisms within the weld were elucidated based on quantitative calculations of the chromium and nickel equivalent ratios. The microstructure of the LaserZ in all welds is predominantly martensitic due to the rapid cooling rate, which makes the tensile properties of the weld higher than the base metal (BM). The results of this study provide technical support for realizing high-efficiency and high-performance single-pass HP-LAHW of thick SSCP.

Finite element analysis of wire EDM process parameters on performance characteristics of Al–SiC hybrid composite with micro and nano reinforcements

Aluminum Hybrid Composites (AHC) microchannels find extensive applications in aerospace, refrigeration and air conditioning (RAC), microelectronics, automotive, biomedical, and marine industries due to their improved mechanical properties. The combination of lower density, high hardness, elevated thermal and electrical conductivity, superior elasticity, and heightened oxidizing ability at low temperatures makes machining aluminum hybrid composites challenging through orthogonal methods in an open environment. Therefore, it is imperative to investigate the impact of various machining conditions to determine optimal parameter values for microchannel fabrication in aluminum hybrid composite materials. This study aims to identify the ideal machining parameters for Al–SiC micro-SiC nano hybrid composites using wire electrical discharge machining. Four distinct process parameters (pulse on time, gap voltage, wire tension, and wire feed rate) and two response parameters (material removal rate (MRR) and surface roughness (SR)) were considered for process optimization. Additionally, finite element modeling was conducted for the aforementioned process, and the results were compared with experimental outcomes. Single-variable optimization yielded maximum MRR at 125 tons (μs), 25 SV (volt), 12 WT (kgf), and 2 WFR (m/min), and minimum SR at 125 tons (μs), 10 SV (volt), 12 WT (kgf), and 4 WFR (m/min). Single-variable optimization for simulations resulted in maximum MRR at 125 tons (μs), 40 SV (volt), 4 WT (kgf), and 6 WFR (m/min), and minimum SR at 110 tons (μs), 10 SV (volt), 12 WT (kgf), and 2 WFR (m/min). Precise modeling aids in minimizing unnecessary machining, enabling exploration of a broader range of experimental results, thereby promoting environmentally friendly and sustainable machining practices.

Investigation into the Impact of Groove Shape on the Tensile Strength of Commercial Steel

In the industrial landscape, welding holds a prominent position, with a significant demand for both effective and high-quality welding processes. Manufacturers, striving to maintain competitiveness, rely on their manufacturing engineers and production personnel to swiftly and efficiently establish manufacturing processes for new products. Among the various welding methods employed, Gas Metal Arc Welding (GMAW) stands out as one of the most widely utilized processes. Several input factors, including welding current, welding voltage, gas flow rate, wire feed speed (WFS), wire size, and welding speed, play a crucial role in determining the quality of welding outcomes. Taguchi's design, recognized for its effectiveness, serves as a powerful optimization tool for enhancing the quality and performance output of manufacturing processes. In this particular study, GMAW was employed to weld commercial steel under predetermined factors of welding voltage, WFS, and groove shape. The X-groove welding exhibited lower tensile strength and hardness compared to V-groove weldments. Utilizing Taguchi's design, the objective was to identify the optimal process factors that would result in higher tensile strength and hardness. The analysis revealed that welding groove shape had the most significant impact on both tensile strength and hardness, followed by voltage. In contrast, WFS exerted the least influence on tensile strength and hardness. The optimized combination of welding factors identified was a V-groove shape, 20 V welding voltage, and a 5.9 m/min WFS.

ELECTRODE WIRE FEEDER FOR MIG/MAG AND TIG WELDING PROCESSES

The electrode wire feeding mechanisms of welding machines are designed to transport the electrode wire from the spool to the welding zone at a constant, predetermined speed or at a speed that varies according to a given law. One of the most promising areas for improving arc welding and surfacing equipment is to control the transfer of electrode metal by pulsing the electrode wire. Therefore, the feeding mechanisms of welding machines must ensure compliance with the conditions of continuous feeding at a constant speed or pulsed feeding with an intermittent movement. The problem of forming pulses with the required parameters can be solved by feeding mechanisms with a vibration drive. The main advantage of such a technical solution is the ability to produce pulsed motion with controllable frequency and amplitude parameters. Due to the high resolution of movement and high dynamic properties in transient motion modes, vibration-driven feeding mechanisms are able to provide high accuracy of bar material feeding into the working area of technological equipment. The principle of operation of such a mechanism is based on the transformation of spatial vibrations into linear displacements. The analytical dependencies obtained in this work allow us to determine the parameters of electrode wire movement by the vibratory feeding mechanism. The proposed technical solution makes it possible to provide different movements of the wire along its axis, and changing the pulsation mode is made possible by adjusting the oscillation frequency of the drive.

Investigation on dual wire TIG Arc additive manufacturing of IN625 and SS316L FGM for continuous gradient and sandwich structures

Fabrication of functionally graded material (FGM) has been studied using dual wire WAAM-TIG (wire arc additive manufacturing - tungsten inert gas) process. The experimental research aims to perform the feasibility study of different designs of FGMs, including continuous gradient (CG-FGM) and sandwich structures (SW-FGMs). The weight percentage of two wire materials, SS316L and IN625, was precisely controlled using individual wire feeding systems. Process parameters were identified to obtain the defect-free deposition for the desired combination of weight percentage. The governing elements, i.e., Ni and Fe, showed a gradual variation in the case of CG-FGM and alternate peaks for SW-FGMs while examined using energy-dispersive X-ray spectroscopy (EDS). The alternate material distinction was noticeable with the increase in the number of individual layers for each set of SW-FGMs. The microstructure evolution of CG-FGM showed a smooth transition from equiaxed to columnar dendrites along the build direction, while SW-FGM showed heterogeneous behaviour. The hardness was steadily increasing in CG-FGMs and formed a wavy pattern in SW-FGMs. X-ray diffraction (XRD) analysis confirmed the formation of the austenitic phase, and variation in peak heights correlates to the change in microstructure and hardness. The conducted tribological study showed the specific wear rate gradually decreased with an increase of Ni content in CG-FGM, whereas in SW-FGM, it showed a strong dependency on the adopted design. The alloying effect in SW-FGM with different design modalities and its comparison with equal weight percentages were also studied in detail and presented.

Achieving a Columnar-to-Equiaxed Transition Through Dendrite Twinning in High Deposition Rate Additively Manufactured Titanium Alloys

AbstractThe coarse β-grain structures typically found in titanium alloys like Ti–6Al–4V (wt pct, Ti64) and Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242), produced by high deposition rate additive manufacturing (AM) processes, are detrimental to mechanical performance. Certain modified processing conditions have been shown to lead to a more refined grain structure, which has generally been attributed to a change in the solidification conditions with respect to the experimental Hunt diagram proposed by Semiatin and Kobryn. It is shown that with Wire Arc AM (WAAM) increasing the wire feed speed (WFS) is effective in promoting a columnar-equiaxed transition (CET). Conversely, estimates of the dendrite-tip undercooling using the KGT model suggest that this will be too small for free nucleation without the addition of artificial nucleants, due to the very low solute partitioning in Ti alloys. It is also shown that it is difficult to promote a CET with plasma transferred arc WAAM as computational fluid dynamics (CFD) melt-pool simulations indicate that the solidification parameters remain within the columnar region on the Semiatin-Kobryn Hunt map, within the constraints of a stable process. However, a high fraction of twin boundaries was observed in the refined β-grain structures seen at high WFS. This has been attributed to departure of $$\left\langle {001} \right\rangle _{\beta }$$ 001 β alignment from the direction of maximum thermal gradient, caused by the curvature of the fusion boundary, stimulating dendrite twinning during solidification. In addition, it is shown that increasing the WFS leads to a change in melt-pool geometry and a reduction of remelt depth, which promoted dendrite twinning and grain refinement.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 1 — Microstructure

Laser welding with cold versus hot wire feed was employed as a root pass to weld X80 pipeline steel. The influences of wire feed rate and preheat on the fusion zone microstructure were investigated. Increasing the wire feed rate helped generate acicular ferrite in the weld metal, and preheating the wire further suppressed the formation of bainite. The acicular ferrite in the upper region of the fusion zone was finer than that in the lower region, which was due to an increase in nucleation sites available. Five fill and cap passes were applied by gas metal arc welding to fill the remaining top part of the groove. Compared to arc welding with a higher heat input, laser welding led to finer prior austenite grains and smaller bainite packet size in the coarse-grained heat-affected zone and limited the formation of martensite-austenite constituents in the intercritically reheated coarse-grained heat-affected zone.

Experimental investigation to assess the surface integrity in WEDM of Al-based hybrid composite material

Aluminum-based hybrid composites are used in various engineering applications due to their unique properties, such as high strength, good wear resistance, excellent corrosion resistance, and low density. Aluminum metal matrix (AMMC) composites reinforced with ceramic particles can be more difficult to machine than traditional aluminum alloys because of their increased hardness and abrasiveness. Wire electric discharge machining is a non-traditional machining process that uses a thin metal wire, typically made of molybdenum, brass or tungsten to cut through a workpiece using electrical discharge sparks. This process is useful for precision machining of complex shapes and profiles in hard or difficult to machine materials. WEDM is a commonly used process for cutting Al-SiC-ZrO2 HAMMCs due to their hardness and difficulty in machining using conventional techniques. The present study examines the relationship between machining parameters like pulse on time (TON), pulse off time (TOFF), peak current (IP) and wire feed (WF) and material removal rate (MRR) and surface roughness ( Ra) for Al-SiC-ZrO2 in WEDM. The Box-Beckham Design was used to plan the experiments, and response surface method was employed to develop the models. The pulse duration, TOFF, IP, and quadratic terms of [Formula: see text] and [Formula: see text] are the most influential factors of the MRR. The TON, IP and interaction term (TON × IP), and [Formula: see text] were the most significant factors for Ra. Multi-response optimization of process parameters was obtained using the desirability function approach. Furthermore, the machined samples were analyzed for surface integrity using SEM techniques. The prediction from this model validated the confirmation results.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 2 — Mechanical Properties

In Part 1 of this study, the influences of feed rate and preheat of the wire on the fusion zone microstructure of X80 steel laser root welds were investigated. Part 2 of this study reveals the effect of cold versus hot wire feed on mechanical properties. Although strength overmatching with the X80 base metal was maintained, the wire alloying elements reduced the hardness of the upper region of the laser fusion zone but had limited effect on the bottom of the fusion zone due to the incomplete mixing of the filler material with the base metal in the bottom root region of the joint. The addition of ER70S-6 filler wire improved the impact toughness of the weld metal at 0°C, due to the formation of an acicular ferrite microstructure. As the temperature decreased to –20°C (–4°F) and –45°C (–49°F), ductile to brittle transition occurred, leading to lower weld metal toughness.

Experimental investigation of the impact of GMAW welding parameters on the mechanical properties of AISI 316L/ER 316L using quaternary shielding gas

In this study, the parameters of Metal Inert Gas (MIG) and Metal Active Gas (MAG) were investigated of AISI 316L/ER 316L. A quaternary shielding gas mixture consisting of Argon (Ar), Helium (He), Carbon Dioxide (CO2), and Nitrogen (N2) was chosen. The Taguchi orthogonal array (OA-L9) methodology was employed to explore optimal welding settings, including arc current (120A, 160A, 200A), wire feed rate (3, 3.5, 4 m min−1), and shielding gas combination (G1, G2, G3). The findings highlighted the importance of shielding gas in influencing the ultimate tensile strength (UTS), elongation percentage (EL%), and material toughness of welding joints. Notably, the highest UTS (515.77 MPa), EL% (20.85%), and material toughness (133J) were achieved by the specific group gas combination shown as G1. It is recommended to configure welding parameters to an arc current of 160A, a wire feed rate of 4 m min−1, and the G1 gas combination. Welded specimens using a G1 gas mixture showcased the best UTS and EL%. Additionally, it was found that the fusion zone (FZ) and heat-affected zone (HAZ) hardness are most profoundly influenced by the choice of gas combination (G2), resulting in the best hardness values of 253.79 HV and 239.68 HV, respectively. The optimal parameters for achieving the desired material hardness were precisely identified as (120A, 3 m min−1, G2). These insights offer a pathway to enhance welding performance and, in turn, elevate the quality and efficiency of industrial applications.

Parametric influence and effect of cooling channel on bead geometry profiles of ER70S-6 manufactured using wire arc additive manufacturing

This study investigated the complex relationship between key process parameters and their effects on weld bead geometrical profile in wire arc additive manufacturing (WAAM) of ER70S-6 low-carbon steel for part production. Specifically, the influence of wire feed rate (WFR), traverse speed (TS), and voltage (U) on weld bead height (WBH), weld bead width (WBW), and weld bead penetration (WBP) was meticulously analyzed. Research methodology integrated the Taguchi technique, analysis of variance (ANOVA), regression modeling, and gray relational analysis (GRA) to investigate and optimize process parameters. Results revealed distinct patterns, with increasing WFR leading to proportional increases in WBH, while elevated TS or U results in reduced WBH due to their impact on arc behavior and heat input. Conversely, WFR and U exhibit notable effects on WBW and WBP, underscoring the importance of optimizing process parameters for desired weld bead geometries. To tackle multi-objective optimization, GRA efficiently determines optimal process parameters for WBH, WBW, and WBP: WFR at 6 m/min, TS at 4 mm/sec, and U at 24 V. Furthermore, the inclusion of a cooling channel beneath the substrate plate significantly influences weld bead geometry, enhancing WBH and WBW while impacting WBP. The cooling channel’s ability to dissipate heat promotes faster solidification, ultimately improving weld bead quality and integrity. These findings offer valuable comprehensions for improving WAAM processes and enhancing the efficiency and quality of part fabrication.

Experiment Comparative Analysis of Feed Rate with Velocity Control in Cutting Mono Crystalline Silicon Using a Diamond Wire Saw.

Fixed-diamond abrasive wire saw cutting is one of the most common methods for cutting hard and brittle materials. This process has unique advantages including a narrow kerf and the ability to use a relatively small cutting force. In the cutting process, controlling the main process parameters can improve the processing efficiency, obtaining a better processing surface roughness. This work designs the PI controller (Proportional-Integral controller) based on the reciprocating wire saw cutting process. The control objects are the workpiece feed rate and wire saw velocity, and the control objective is the normal cutting force. For the control trials, several reference values of various normal cutting forces were chosen. The effects of feed rate and saw velocity on the cutting surface finish and cutting time were investigated in this work using wire saw cutting analysis on a square monocrystalline silicon specimen. The results of this study showed that under a constant applied force of 2.5 N, the optimal feed rate of the diamond wire through the specimen could reduce cutting time by 42% while achieving a 60% improvement in the measured surface finish. Likewise, optimal control of the wire saw velocity could reduce cycle time by 18% with a 45% improvement in the surface finish. Consequently, the feed speed control is more effective than the wire saw velocity.

Robotic welding system for adaptive process control in gas metal arc welding

Changing process conditions such as distortion, varying seam preparation or gap width during welding is a major challenge in automated gas metal arc welding (GMAW). While human welders can adjust the process during welding (e.g. welding speed, torch orientation), an automated welding system needs sensors to detect and actuators to adjust the process. Adjusting the process in response to changing process conditions is usually referred to as adaptive welding. The aim of this work is to build a robotic welding system capable of automatically adapting the welding process using some of the approaches of a human welder. To enable adaptive process control, a robotic welding system is built. It consists of four main components: a six-axis industrial robot for mechanical guidance of the welding torch, a welding power source, a monochrome visual camera as an image sensor and a process controller that combines the three components. The camera captures images of the weld pool during welding and processes the images to provide geometrical information such as the width of the weld pool and the position of the weld pool front. Changes in the weld pool geometry are quantified, and an adjustment strategy is generated in the process control unit in real time. Process adjustments can be mechanical (e.g. welding speed, torch orientation) and electrical by adjusting synergic process settings (wire feed speed, arc length, process dynamics). Validation tests demonstrate the functionality of the welding system. Two use cases were investigated. Firstly, a deposited weld bead was examined, and variations in the width of the weld pool were induced by varying the welding speed. The second application was a seam tracking application. The path is pre-programmed, and the specimen is positioned with an offset to the path. Compensation for the offset is implemented.

Integrated approach to Wire Arc Additive Manufacturing (WAAM) optimization: Harnessing the synergy of process parameters and deposition strategies

The flexibility of Additive Manufacturing (AM) technologies in the metal 3D printing process has gained significant attention in research and industry, which allows for fabricating complicated and intricate Near-Net-Shape (NNS) geometry designs. The achievement of desired characteristics in Wire-Arc Additive Manufactured (WAAM) components is primarily contingent upon the careful selection and precise control of significant processing variables, including bead deposition strategy, wire materials, type of heat source, wire feed speed, and the application of shielding gas. As a result, optimizing these most significant process parameters has improved, producing higher-quality WAAM-manufactured components. Consequently, this has contributed to the overall rise in the method's popularity and many applications. This article aims to provide an overview of the wire deposition strategy and the optimization of process parameters in WAAM. The optimization of numerous wire deposition techniques and process parameters in the WAAM method, which is required to manufacture high-quality additively manufactured metal parts, is summarised. The WAAM optimization algorithm, in addition to anticipate technological developments, has been proposed. Subsequently, a discussion ensues regarding the potential for WAAM optimization within the swiftly growing domain of WAAM. In the end, conclusions have been derived from the reviewed research work.

Experimental Study on Wire Melting Control Ability of Twin-Body Plasma Arc

The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer, which is beneficial to shape and property control in wire arc additive manufacturing. In this paper, with the wire feeding speed as a characteristic quantity, the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio (under the condition of a constant total current), the wire current/main current and the position of the wire in the arc axial direction. The results showed that under the premise that the total current remains unchanged (100 A), as the current separation ratio increased, the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power, the first melting mass range remained constant; the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed, and the second melting mass range was expanded. When the wire current increased, the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount; however, when the main current increased, the plasma arc power was the only factor causing the increase in the wire melting amount. The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power. The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested. When the current separation ratio increased and reached a threshold, the middle melting amount remained constant with increasing wire-torch distance. When the current separation ratio continued to increase and reached the next threshold, the maximum melting amount remained constant with the increasing wire-torch distance. The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio. Through this study, the decoupling mechanism and ability of this innovative arc heat source is more clearly.

Effect of laser beam wobbling and welding speed in X80 steel wire-fed laser root welds

A wobble laser was combined with a wire feed during laser root welding of X80 pipeline steel. The enlarged laser irradiation area and molten pool resulting from the laser beam wobbling provided a better gap-bridging ability, which is critical during laser welding of thick pipes. Applying laser beam wobbling enabled better control of filler metal dilution, which determined the weld metal microstructure and mechanical properties. In the present work, more bainite along with reduced acicular ferrite was formed in the wobble laser weld, due to the effect of dilution resulting from increased base material melting during wobbling beam, along with an inhomogeneous fusion zone microstructure. The instrumented indentation testing was utilized for the first time to distinguish the local yield strength variation of different regions of the fine weld zones, allowing one to verify if the weld metal strength meet the target value in industrial standards. As the productivity being improved when the welding speed increased from 1.0 to 1.5 m/min, the presence of more low temperature transformation products generated with a faster cooling led to a 26 HV higher hardness and a 70 MPa higher yield strength in the upper region of the fusion zone.

Molding performances of ZL205A aluminum alloy fabricated by wire arc additive manufacturing based on gray correlation theory

Evaluation indicators such as aspect ratio, dilution rate, microhardness, wear resistance and electrochemical corrosion resistance are crucial to assess the quality of arc additive manufacturing of aluminum alloys. This paper investigated the impact of the process parameters of the Cold Metal Transfer (CMT) arc additive manufacturing on molding performances of single pass-single layer samples. A three-factor, three-level orthogonal table was devised incorporating welding speed, wire feed speed, and dry extension as the three principal process parameters. Combined with the gray correlation theory, the Shape-Performance Coefficient (SPC) was established to provide a comprehensive evaluation of the molding performances of the samples. The results indicated that the priority sequence of the three process parameters on molding performances was wire feed speed, welding speed, and dry extension. The ideal process parameters are: a welding speed of 9 mm/s, a wire feed speed of 4 m/min, and a dry extension of 10 mm. If the wire feed speed is too high and the welding speed is too low, the aspect ratio and dilution rate of the sample will increase, resulting in larger grain size and more porosity defects. This has the consequence of decreased wear resistance and corrosion resistance for the sample. Compared to the ZL205A cast aluminum alloy (CastZL205A), the most exceptional additive manufacturing sample exhibits a ten-fold reduction in the average grain size and a 144.88% increase in electrochemical corrosion resistance. The findings presented in this paper establish data support for thin-walled parts arc additive manufacturing with ZL205A aluminum alloy and provide a theoretical foundation for the repair of critical aluminum alloy components.

Arc and keyhole behavior in narrow-gap oscillating laser-MIG hybrid welding of thick aluminum alloys

Narrow-gap oscillating laser-MIG hybrid welding was developed to weld thick aluminum alloys. Weld formation and porosity defect with various oscillating laser parameters were systematically analyzed. Furthermore, the corresponding influencing factors, i.e., arc and keyhole dynamic behaviors were discussed. The difference between both sidewall penetrations was small while wire feeding speed was high and oscillating laser diameter was lower than 3 mm. When laser oscillating frequency was higher than 300 Hz, porosity was less than 0.5 %. Arc burnt stably and the deflection angles were small while laser oscillating frequency was 300–450 Hz and diameter was 1–2 mm. The small fluctuation of arc resulted in small difference between both sidewall penetrations. With the action of oscillating laser, the charged particles increased and diffused to the upper part of the groove. Therefore, arc was attracted by the charged particles and struck at the center bottom of groove. While the arc burnt stably, the difference between both sidewall penetrations was small. The pore formation was significantly inhibited by oscillating laser, as the keyhole opening size increased and fluctuation degree decreased. With the action of oscillating laser, the ratio of keyhole opening width to depth increased, the probability of Rayleigh jet instability on the keyhole wall was reduced.

Исследование изменения геометрических параметров образцов, наплавленных методом GMAW при воздействии на электрическую дугу продольного магнитного поля

Introduction. The paper presents the results of research of additive manufacturing process by electric arc with axial feeding of steel filler wire in protective gas environment (GMAW technology) with additional influence of external longitudinal magnetic field on electric arc. Purpose of work: an experimental study of the effect of a longitudinal magnetic field during additive manufacturing by an electric arc with axial feed of filler wire made of structural steels in a protective gas environment on the change in the geometrical characteristics of the layers being surfaced. Research Methods. The manufacturing of specimens was carried out on a 5-axis additive machine based on a CNC machine. Surfacing was carried out in the following modes: voltage 17.5 V; current 55–65 A; wire diameter 1.2 mm; wire material Sv-08G2S; wire feed rate 2,267 mm/min; approximate roll diameter 3.0 mm; roll length 50 mm; number of wires per one roll 312.5 mm; number of layers when surfacing the wall 5; magnet operation mode: alternating current with frequency 50 Hz, voltage 30 V; measured magnetic induction 5.7 mTl; initial height of the magnet above the substrate 10 mm; electrode stickout 10 mm; shielding gas: welding mixture CO2-Ar; gas pressure (flow rate) 0.15 MPa. Results and discussion. The conducted experimental study showed that the effect of longitudinal magnetic field had a statistically significant effect on the change in the dimensions of the singular, namely an increase in the width of the layers being surfaced by 34.1 %, with a calculated significance index close to zero, and a decrease in height by 20.2 %, with a calculated significance index equal to 2.7105. The effect of longitudinal magnetic field had a statistically significant effect on the change of the overall dimensions of the specimens consisting of five layers, namely, the width of the specimens increased by 11.2 % with a calculated significance index of 4.3103, and the height of the specimens decreased by 10.3 % with a calculated significance index of 6.3105. The effect of longitudinal magnetic field had no statistically significant effect on the change of the vertical deviation from straightness for the side walls of the specimens, with a calculated significance index of 0.3277, and had no statistically significant effect on the change of the error of the width of the walls of the specimens, with a significance index of 0.098.

Visualization and control of the free-flight transfer phenomenon in the wire feed control process

Gas metal arc (GMA) welding requires improved process stability, higher quality and efficiency, and quantitative control of the heat input and deposition. These requirements can be achieved by appropriately controlling the metal transfer phenomenon. However, this control method has primarily been applied to short-circuit transfer, and very few examples of its application to free-flight transfer exist. Therefore, the effect of wire feed control on free-flight transfer remains unclear. In this study, the influence of wire feed control on the free-flight transfer phenomenon in the GMA welding process using an aluminum wire electrode was investigated through experimental observations, and free-flight transfer control was attempted.It was observed the free-flight transfer phenomenon, particularly globular transfer, under low-current conditions with controlled wire feeding under various feed conditions, using wire feed–retract speeds and cycles as parameters. The observation results revealed two patterns with different timings of droplet detachment under long- and short-period conditions. Furthermore, the observation of the droplet detachment motions revealed that the inertia caused by the acceleration or deceleration of the feed speed acts on the droplet. Moreover, the difference between the two transfer patterns is primarily caused by the inertia acting on the droplet before and after switching the wire feed–retract direction and the size of the droplet at that time. Based on this, free-flight transfer can be stabilized by reconfiguring the feed conditions.