Electrode Metal Transfer Research Articles

The Effect of Energy Parameters of Power Sources on the Structure and Properties of Permanent Joints at Manual Arc Welding

The study presents the results of the research into the effect of the dynamic properties of inverter and diode power sources of welding arc power supply on the stability of melting and transfer of electrode metal into the weld pool. The principal energy parameters of the power source include the rates of rise and fall of short-circuit current, the ratio of arc burning current to short-circuit current, and other related factors. It has been demonstrated that an increase in the rate of change of these parameters within one welding mode microcycle alters the properties of heat and mass transfer, increases the frequency of electrode metal droplet transfer, reduces the size of transferred droplets in the weld pool and the duration of their stay on the electrode end under the influence of the high temperature of the welding arc, and the duration of short circuits. The increase in the mass fraction of alloying elements at their transition from the coated electrode to the weld metal is demonstrated to depend on the rate of change of the main energy parameters of one welding mode microcycle of the inverter power source in comparison with the diode rectifier. An enhancement in the structural integrity and properties of permanent joints during welding has been observed when using an inverter power source for the welding arc with high dynamic properties.

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.

Technological Features of Selection of Parameter Values of Arc Welding Mode in Shielding Gas Mixture Ar + CO<sub>2</sub>

Gas-shielded arc welding today occupies a leading position among the methods for producing permanent joints in industrial conditions. The emergence of new materials with complex alloying and hardening systems makes carbon dioxide, traditionally used as a protective medium, inefficient for use. One of the effective ways to solve these problems is to change the composition of the protective gas atmosphere, which allows you to significantly change the physical and metallurgical processes of melting the electrode wire and the forming the weld. At the same time, the transition to the use of protective gas mixtures based on argon is usually carried out without understanding the essence of the technology and possible problems associated with the specifics of penetration of the base metal, which can cause a number of serious problems. The present paper describes important regularities between technological characteristics of arc welding in a shielding gas mixture Ar + CO2 and welding mode parameters under conditions of deviation of their values from the most effective ones in order to ensure the stability of the processes of electrode metal transfer and the formation of the deposited weld metal bead. On the basis of experimental data, the most probable causes of the appearance of a dangerous and difficult-to-detect defect in the formation of a welded seam in the form of non-fusion between individual beads of the deposited metal and along the fusion line with the base metal of the welded parts have been established. The defect is common and can cause unpredictable failure of the welded joint without visible plastic deformation. Empirical dependences for determining values of the main parameters of the welding mode are proposed as well. Important regularities have been established that make it possible to increase the efficiency of arc welding technology in the environment of protective gas mixtures in the conditions of domestic production.

PERFORMANCE CHARACTERISTICS OF NICKEL-CONTAINING STEEL STRUCTURES DURING MECHANIZED WELDING-SURFACING WITH MODIFIED (DOSED) ELECTRODE WIRE FEEDING

Purpose. To study and analyze in a comparative order the influence of factors of the controlled pulse process of electrode wire supply on some basic mechanical characteristics of seams and welded rollers in the processes of welding and surfacing of nickel-containing steels.
 Methods of research. The study the mechanical characteristics of seams and welded rollers was carried out using modern laboratory equipment and appropriate techniques. This made it possible to determine how the pulse feed parameters affect the strength characteristics of the weld and near the weld zone over the entire cross-sectional area of the weld or weld layer. Detailed characteristics of feed pulses were determined using a welding process analyzer to obtain oscillograms of power parameters of arc combustion with their analysis, including determining the stability of the arc process for different types of pulses. Important for the improvement of welding results is the controlled nature of the electrode metal transfer synchronous with the pulsed movement of the electrode. It is noted that the energy consumption of the arc process during the pulse supply of the electrode wire with an indication of its reduction compared to traditional welding.
 Experimental work was performed using a special electrode wire, which is usually used for welding and surfacing of nickel-containing steels. These processes were carried out in a protective environment of CO2 in automatic mode.
 Results. Due to the fact that the strength characteristics of the weld are among the most important, attention is paid to their definition and analysis. The strength characteristics depend on many parameters, in particular the thermal characteristics of the process, the structure of the weld metal, the presence of non-metallic inclusions and so on. All these factors were studied with the help of appropriate instruments, and on the basis of numerous comparative photos of microstructures on sections of the cross section. The analysis of the sections revealed the types of microstructures obtained, the presence of inclusions and more. It is determined, in particular, that the structure of weld metal in pulsed electrode wire welding differs significantly from the structure of traditional welding in reducing inclusions, finer grains, etc., which improves the mechanical properties of the weld and seam area.
 Scientific novelty. Based on a series of experimental studies, the use of pulse algorithms for the movement of the electrode wire with certain parameters in automatic mode for welding and surfacing of nickel-containing steels to improve the mechanical properties of seams and welded rollers.
 Practical value. It is determined that the method of pulse welding of electrode wire to the controlled variant, including nickel-containing steels is effective and can be widely used in industry using specially designed equipment that provides a suitable process with stronger characteristics.

Development of Self-Shielded Flux-Cored Wires for Arc Welding of Low-Alloy Steels

Current aspects of the developing of modern self-shielding flux-cored wires composition for arc welding of low-alloyed steels are considered. Advantages and disadvantages of flux-cored wires of carbonate-fluorite, oxide and oxide-fluoride types of are shown in comparison. The effectiveness of gas shielding of molten metal at welding with self-shielding flux-cored wires of carbonate-fluorite type is analyzed considering the thermal properties of their cores. It is shown that to improve reliability of gas shielding at welding using the wires of this type it is important not only to ensure generation of sufficiently large volume of shielding gases at thermal destruction of the wire core, but also to control this process, providing gas evolution at all stages of heating and melting of the wire. The results of complex thermal analysis of the wire core mixtures containing, for example, lithium carbonate show substantially large heat losses for heating and melting of the wire core, which are accompanied by the development of energy-intensive processes of thermal destruction of core components. It is shown that the limitation of lithium carbonate content in the wire at the level of not more than 2 wt. % allows not only to preserve welding arc burning stability at the acceptable level but also to provide effective gas shielding of molten metal and easy separation of slag crust. The control of thermochemical reactions in the core is achieved by selection of its proper composition to ensure favorable melting of flux-cored wire and electrode metal transfer to the welding pool. Results of metallographic examinations of distribution and composition of non-metallic inclusions in metal of the welds made with wires of the oxide and oxide-fluoride types are presented. Main properties of the developed self-shielding flux-cored wires and recommendations on welding are given in conjunction with prospective fields of their application.

Determining patterns in the generation of magnetic fields when using different arc welding techniques

This paper reports a study into the levels of magnetic fields induced by arc welding equipment in various ways in order to assess their impact on the body of welders. It is known that welders are exposed to a magnetic field of high intensity. Depending on the welding technique and the type of welding equipment, it may exceed the maximum permissible levels (MPL). Note that new Ukrainian sanitary standards for magnetic fields have been introduced, which regulate their levels depending on the frequency range. Therefore, it became necessary to carry out their hygienic assessment according to the new standards in order to devise appropriate methods for protecting welders. To this end, it was required to choose a new generation of devices to determine the intensity of magnetic fields induced by welding equipment. Based on the analysis of the constructed oscillograms and spectrograms of magnetic fields, it was found that semi-automatic welding with a metal electrode in carbon dioxide is characterized by an increased level of magnetic field in the frequency range of 50‒1000 Hz. With automatic arc welding under the flux, there are no excess of the maximum permissible levels of individual harmonics of the magnetic field but there is an excess of the total value of all harmonic components of the magnetic field. Manual arc welding with direct current involving a non-melting electrode in argon is characterized by a moderate level of magnetic field in workplace. During manual arc welding with coated electrodes, the exceeded level of the magnetic field is observed only on the electrode cable itself. It is shown that the spectral composition of the magnetic field signal is determined mainly by the welding technique itself, the peculiarities of arc combustion, and the nature of the transfer of electrode metal in the arc gap, as well as the initial parameters of the power supplies of the welding arc

Stabilization of the process of mechanized pulsed-arc welding

The main disadvantage of the mechanized arc welding process in shielding gases with short circuits is the spatter during melting of the electrode metal and its transfer to the weld pool, which affects the productivity of the process, reducing it. Its elimination is possible through the implementation of the controlled transfer of molten electrode metal into the weld pool. The implementation of such a transfer and the control of the processes that take place in the arc gap to a large extent determine the conditions for the qualitative formation of the deposited metal, the stability of the process, the magnitude of the loss of electrode metal and the manufacturability of the processes of arc welding in shielding gases. At the present stage of development of welding technologies, controlled transfer of electrode metal is possible due to the pulsed nature of arc burning. In this case, one of the main methods for increasing the efficiency of the process is to limit the maximum value of the short circuit current by increasing the inductive resistance of the welding circuit.
 The research aimed to determine the effect of the rate of rising of the welding current during a short circuit on the stability of the welding arc. It was found that an increase in the current growth rate, starting from 1.23 kA/s to 50 kA/ s, leads to a decrease in the average duration of short circuits by at least 10 times. At the same time, the average frequency of short circuits increases by more than 2 times, from 36...38 s-1 to 80...86 s-1. The reason for this is the increase in the values of the electrodynamics’ Lorentz force, the action of which leads to the compression of the liquid metal bridge of the drop (pinch effect) due to an increase in the short circuit current. At the same time, there is a violation of the stability of the pulse process, and this is reflected in an increase in the average frequency of arc breaks by more than 30 times from 0.33 s-1 to 10 s-1. An increase in the energy parameters of the welding process led to a decrease in the average frequency of short circuits (2...3 times) and their average duration (2 times). The reason for this should be considered a change in the type of transfer of liquid metal – the welding process with short circuits has turned into a mixed process in which, along with short circuits, a droplet transfer of electrode metal is observed.

Arc Technological Characteristics and Metal Transfer Behavior of Twin Electrode GMAW Deposition

Experiments proved that the arc voltage influences its spatial form and electrode metal transfer behavior characteristics during twin electrode GMAW with a single power source. Two specific arc forms were revealed for two corresponding types of metal transfer. The V-shaped arc exists on the melt drop common to the two consumable wires at voltage rate 24-27 V. The columnar shaped arc is formed due to voltage increase up to 34-36 V, which results in increased mobility of the cathode spot in the weld pool surface. As a result, the arc travels between the ends of two electrode wires, and the metal is transferred in drops of small size. It was demonstrated that for the common drop formation the gas mixture of 82% Ar+18% CO2 is preferable to pure argon. It decreases the surface tension on the boundary between the melted electrode metal and the vapor-gas mixture, resulting in the increased volume of the common drop. It was found that a consistent common arc from two electrode wires decreases dilution is made up 43%, which is 1,65 times more and improves the deposited metal formation quality.

Investigation of the Criteria for Evaluating Electrode Metal Transfer in Short Circuit Gas-Shielded Arc Welding

Based on the developed information-measuring complex, the investigation of processes of melting and electrode metal transfer during short circuit arc welding was carried out. The close relationship between the energy of the arc at the stage of its formation and the diameter of an electrode metal droplet was found. It is proposed to evaluate the transfer stability by the harmonic composition of welding current.

On the solution of the problem of synthesis of the control system for the process of dosed feed of electrode wire for arc welding equipment

Goal. Refinement of the methodology for the development of an effective control system for an electric drive with controlled relay-type regulators for organizing a metered feed of an electrode wire using the parameters of the arc process with the possibility of using it in design practice and practice of technological application. Methodology. The proposed method for the mathematical description (mathematical model) of the system of the developed structure electric drive - arc process with current feedback of welding with a variable structure device is based on the theory of automatic control as applied to nonlinear elements, the application of the theory of operational calculus. At the same time, a selection and description of a nonlinear node in the feedback circuit in the form of a relay element with a certain structure and subsequent linearization of this element was made. As an electric motor of the electrode wire feeder, a new development of a specialized valve electric motor is used, which is used in the system with a microprocessor controller. Results. Due to the presence of a substantially nonlinear link, the calculation of the valve electric drive system – the arc process can be found on the basis of a system of nonlinear differential equations, which is practically impossible for practical application. In this work, these complications are overcome on the basis of a rational choice of the description of the nonlinear link, its harmonic linearization and obtaining on this basis a mathematical description of the system, from which, using the methodology of operational calculus, the relations necessary for calculating the parameters of the system are determined in analytical form. Originality. The problem of calculating a rather complex problem of mathematical description of the valve electric drive system – a technological link in the form of an arc process with a substantially nonlinear link in the feedback circuit in the work is solved with the effective use of a set of methodological methods, which include as a means of representing individual links, including nonlinear links selected simplifications and solutions of the obtained differential equations using original methods of operational calculus. The proposed method (mathematical model) is tested in two directions – oscillography of a real system, as well as system simulation. Practical significance. Using the developed methods for describing the control system, it is possible to calculate its characteristics and, on their basis, select the parameters for setting the electric drive controller, which allows, without additional experimental research, to obtain the necessary character of the transfer of electrode metal, and, consequently, the quality of the result of the arc process.

State and development directions of systems and methods for electrode metal transfer, joint and surfacing layer formation control during electric arc mechanized and automatic welding—surfacing

The problems that are associated with solving the problems of energy saving, improving in the quality of welded seams and deposited layers in mechanized arc welding and surfacing processes are considered. Shown is wide range of technical and technological methods, influences, techniques that allow to greater or lesser extent to solve these problems with the use of basic and additional hardware, and with the use of new electrode materials, protective media and activating materials. Particular attention is paid to equipment using pulse algorithms of functioning, as well as combined systems of influence on the arc process, which will allow covering wider range of effect on the formation of welded seams and deposited layers. Some of the technical and technological solutions require further researches in terms of specific tasks of welding and surfacing production, as well as the choice of affordable and perfect element base and material resources.

Determination of Parameters of Electrode Metal Transported Drops by Simulation and Visualization

The nature of the molten electrode metal melting and transfer is the main process parameter of manual metal arc welding (MMA) with coated electrodes. It significantly affects the efficiency of the welding process. For this reason the relevant task is to identify the parameters of the transferred molten electrode metal drops and their further transfer into the weld pool with maximum accuracy. The aim of the given paper is to develop a method and visual representation of the form and the geometrics (volume, area, mass) of a molten electrode metal drop.We have developed the method of simulation modeling and visualization for molten electrode metal drops transfer and their parameters. It allows obtaining highly reliable input data to be used for developing and verification of mathematical models for the thermal fields distribution along the welded item surface. The algorithm is realized as the calculation programs for specifying the molten metal drop parameters and means of its geometrics and space form visualization.We used this method to specify a number of molten electrode metal drop parameters: volume, mass, center-of-gravity position, surface area.We have established that it is possible to conduct the measurements with maximumThe suggested method significantly decreases the labor intensity of experimental studies aimed at specifying the size of electrode metal drops in comparison to the standard methods. When we know the size of the drops under certain welding conditions we can control the drop transfer process, i. e. reduce the heat input into the welded item and produce weld joints with the tailored performance characteristics.

Characteristics of droplet transfer of electrode metal during MMA depending on the chemical composition of the material of the rod of the coated electrode

This article presents the results of experimental studies of the effect of the coated electrode material for MMA welding on the droplet transfer parameters of electrode metal. It has been established that the use of coated electrodes based on copper (OZCH-4) and aluminum (Castolin EC 4001) alloys, compared to traditionally used metal rod based electrodes (Sabaros me20|10, LB-52U), affects the mass transfer characteristics of droplets electrode metal, in the form of an increase in the average duration of arc burning at intervals of melting of the electrode and the period of formation of drops of electrode metal up to 4 times.

ИНФОРМАЦИОННО-ИЗМЕРИТЕЛЬНЫЙ КОМПЛЕКС ДЛЯ ИССЛЕДОВАНИЯ ПРОЦЕССОВ ПЛАВЛЕНИЯ И ПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА ПРИ ДУГОВОЙ СВАРКЕ

The purpose of the paper consists in the description of the procedure for investigations and software-hardware means for arc welding with a melting electrode in protective gas environment with the controlled transfer of electrode metal and its visualization. 
 For investigations of quick electrode metal transfer processes there was used Evercam 1000-4-C digital video-camera and RKDP-0401recorder of welding mode parameters. 
 For video-control of the process there was used a method of active illumination with the further image filtration. It is determined that the visualization of a welding drop transfer dynamics during arc welding with melting electrode in protective gases should be carried out in the infrared range on one side limited with the curve of a spectral transmission of light filters – 950 nm, and on the other side of a matrix sensitivity spectral curve of a rapid camera -1050 nm. 
 There is developed software in the environment of the LabVIEW graphical programming allowing the fulfillment of adjustment and programming welding mode parameters and high-speed shooting, device synchronization, superposition on oscillograms of electric parameters of the electrode metal image transfer, definition of power characteristics at different interval of drop transfer. 
 The CMT (Cold Metal Transfer) process with the aid of the equipment of Fronius TransPuls Synergic 3200 is investigated. It is defined that for arc welding in protective gases an optimum frequency of video-shooting is 1500-2000 shots per second at resolution from 640x608 pixels to 320x400 pixels that allows analyzing efficiently rapid processes of drop transfer.

Effect of Protective Coatings in Welded Constructions on Welding Stability and Electrode Metal Transfer into a Weld Pool in MMA

The paper presents data of experimental research into the importance of protective surface coatings in welded products for MMA stability; heat field distribution patterns on their surfaces, and structure and phase composition of the welded metal. The study has revealed that a protective surface coating in a welded item in MMA has a positive effect on shortcut duration, increasing it by 5-11 %, raising its formation and transformation time by 10-12 %; 15% dimensional increase of a welded metal grain is registered as well, and a heat impact zone expands by 25%.

Electric Arc Deposition of an Anticorrosive Layer with Two Strip Electrodes

A two-strip electrodes surfacing with controlled transfer of electrode metal is proposed for applying an anti-corrosion layer to the surface of the base metal with a variable angle to the horizon. To prevent the formation of defects in the formation of the deposited layer, it is proposed to adjust the parameters of the surfacing mode in places where the angle of inclination of the surface changes.

Heat and Mass Transfer Kinetics in Arc Welding Process

The paper presents the investigation results of the heat and mass transfer kinetics during shielded metal arc welding (SMAW). It is shown that instability of the electrode melting and metal transfer to the molten pool is mostly caused by a system of forces acting on the metal droplet at the continuous electrode tip. Experiments show that the process instability and spatter of the electrode metal depend on the energy parameters of the SMAW mode. At the same time, the SMAW technology can be significantly improved through the implementation of the energy parameter control by the adaptive pulsed-arc welding method.

Procena negativnog uticaja koncentracije mangana u gasovima od zavarivanja na zdravlje zavarivača i kako da se taj uticaj smanji

The article presents the results of a theoretical study (literature review of publications), which allowed to establish the negative impact of welding aerosol (manganese and other elements) on the human body: you can use special welder protection equipment (ventilation and individual welder protection); reduce the quantitative and qualitative content of manganese welding aerosols (welding technology, power sources, modern welding materials); reduce the content of manganese in the human body, removing it with medicines. Experimental studies have shown that the use of an inverter power source, compared with a diode rectifier, contributes: to ensuring the drop-by-drop transfer of electrode metal to reduce the time of their formation by 46% and the transition by 28%; ensures the transition of alloying elements from welding materials to the weld metal by 6% and reduces its losses from the fusion line by 6% and HAZ by 3%; to reduce the intensity of education (g / min) SA and their components by 23%; to reduce the specific allocation of CA and their components by 23%.

Эффективная мощность сварочной дуги обратной полярности при наплавке алюминия плавящимся электродом

The paper analyzes the information about the effective power of a reverse polarity arc on an aluminum part and the influence of the arc cathode region on it. The study differentiated the effective power of the direct polarity arc into its main components. The authors carried out the experiments to measure the effective power of the reverse polarity arc for aluminum welding. To determine the effective power, the calorimetry was used when hardfacing a wire of 1.2 mm diameter on the Al-Mn alloy plate and the deposited metal then was weighed. Based on the experiment results, the authors calculated an average algebraic deviation of αН∙I hardfacing performance and effective power. As a result, the authors proposed the procedure to determine the electrode wire fusion coefficient at zero stick-out α0 according to its dependence on the arc current, which increases at electrode diameter decreasing. This coefficient is about 25 % less than that of steel. By assuming a weak dependence of anode power on the arc current, this fact proves the obtained data on the high heat content of electrode metal droplets of an aluminum wire in comparison with a steel wire. At the droplet transfer of electrode metal, the cathode region power of the arc makes the prevailing contribution to the total effective power of the reverse polarity arc. At the current density equal to 175 А/mm2, the specific effective power of the cathode region action is qSC=9.0 W/А, the power of the electrode metal is qE=4.6 W/А, and the plasma flow power is qP=5.2 W/А.

Ремонт поверхневих дефектів на діючих трубопроводах MIG/MAG зварюванням в імпульсному режимі

A significant part of Ukraine’s trunk pipelines have been in operation for a long time and require renovation. The most common method of repair is welding of defective areas with corrosion damage using arc welding. But while performing welding work on active pipelines there is a danger of through-penetration or excessive heating of the pipe wall with the welding arc, which can lead to its destruction by internal pressure. The problem of safe repair of the surface defects in pipelines under pressure can be solved by reducing the thermal effect on the pipe wall. Experimental investigations of heat propagation while welding rollers on a 17GS tube steel plate by manual arc welding and semi-automatic MIG/MAG welding with the controlled transfer of metal in the impulse mode were carried out in the article. At the same time, measurements of temperature changes in the wall of the pipe at six points at different depth were taken, using K-type chromel-alumel thermocouples connected to the Arduino microcontroller, and their subsequent processing. Macrostructural investigations were conducted and the depth of penetration and the zone of thermal impact of the welded rollers were determined. The results of the research have shown that by MIG/MAG welding in impulse mode, the maximum pipe wall temperature is 168 ° C (31 %) lower than with manual arc welding. Also, in this method, the cooling rate is higher. Such reduction in heat input is significant and minimizes the risk of thermal burn of the pipe wall. By welding in impulse mode, the quality of the welded rollers is much better, the depth of penetration decreases and the thermal impact zone is three times smaller. The use of MIG/MAG impulse mode welding of drop transfer of electrode metal in the repair of the surface defects of the pipe wall has been found to be more efficient and productive than the manual arc welding, as well as safer and more economical, as it guarantees quick and efficient repair without the risk of thermal burning of the pipe wall.