Electrode Metal Transfer Research Articles

Regularities of Control of Mechanized Pulse-Arc Welding Process for Ensuring its Stability

Mechanized arc welding in protective gases with short circuits (s.c.) is performed at moderate values of the welding current (up to 180 ... 220 A) and at the relatively low voltage (18 ... 24 V) on the arc. The main disadvantage of the process is spattering when melting an electrode metal and when transferring it to a weld bath. The elimination of disadvantages is possible through the implementation of a controlled transfer of molten electrode metal to a welding bath - due to the pulsed nature of arc burning. At pulse-arc welding (PAW), one of the main methods of increasing the efficiency of the process is to limit the maximum value of the short-circuit current Imax s.c. by increasing the inductive resistance L in the arc-welding circuit. Proceeding from the features of mechanized arc welding, the purpose of the research is to specify the influence of the velocity of the growth of the welding current vс during the s.c. on the arc stability. The implementation of experimental work presupposes surfacing on a plate with the programming of the operating mode of the inverter at different values (9, 12, 15, 18, 21, 24, 27, 30) with the frequency f = 25 Hz and a pulse ratio C = 2. While analyzing oscillograms of welding current and processing their records, it was established that a decrease of the velocity of the welding current growth leads to a significant limitation of the maximum value of the short-circuit current. The statistical processing of the momentary values of the welding current shows that the increase in the velocity of current growth vс starting with vс = 1.23 kA / s to vс = 50 kA / s makes the average short-circuit duration 10 times shorter. At the same time, the average frequency of short circuits grows more than twice. The increase of vс leads to the destabilization of the pulse process and this is reflected in the 30-times increase of the average frequency of arc break. The increase of the energy indexes of the PAW to the Iav. = 220 ... 225 A, Uav. = 24.5 ... 25.9 V, Q ≈ 7.9 ... 8.0 kJ / cm led to the changes in the parameters which characterize the process of pulsed welding with short circuits. There is a sharp decrease in the average frequency of short circuits (2 ... 3 times as rarely) and the average duration of s.c. (twice shorter).

RESEARCH OF PROPERTIES OF THE METAL OF THE HEAT-AFFECTED ZONE FOR SURFACING BY STAPE ELECTRODE WITH THE CONTROLLED TRANSFER OF THE ELECTRODE METAL

The quality of the deposited layer is determined by the conditions of its formation, as well as the properties of local zones, due to the parameters of the thermal cycle of surfacing (mechanical, microstructural, chemical, etc.). When surfacing the austenitic layer on pearlitic steels, the properties of the heat-affected zone, along with the resistance of the surface layer to corrosion, largely determine the performance and durability of the deposited product. To reduce the amount of heat input and effectively control the structure and properties of the heat-affected zone when restoring working surfaces by submerged arc surfacing, a method for surfacing with a tape electrode with controlled mechanical transfer of electrode metal is proposed. Studies have shown that the imposition of longitudinal sinusoidal vibrations on the end of the tape electrode can reduce the level of heat input in the heat-affected zone by increasing the efficiency of fusion of the base metal. At the investigated frequency of 50 Hz, the duration of the dots on the boundary of the fusion line and below it in the range 900 ... .1100 °С is less than when surfacing without controlled mechanical transfer. Reducing heat input into the heat-affected zone in the temperature range 900 ... 1100 °С provides a finer-grained structure. The use of forced vibrations of the end of the tape when surfacing a high-alloy austenitic layer on low-carbon steel makes it possible to obtain a finer-grained structure at the fusion boundary in the heat-affected zone. This will increase the resistance of the heat-affected zone to the formation of defects associated with a decrease in its mechanical properties.

МОДЕЛИРОВАНИЕ ПЕРЕНОСА МЕТАЛЛОВ МЕЖДУ ЭЛЕКТРОДАМИ ЦИЛИНДРИЧЕСКОЙ ФОРМЫ ПРИ ЭЛЕКТРОИСКРОВОМ ЛЕГИРОВАНИИ

The work is dedicated to the simulation of the processes of erosion and electrode metal transfer at coating formation by an electrospark alloying method. Anode is a cylindrical rod, and cathode – a disk. During discharge pulses the erosion takes place both in anode material, and in cathode material. The anode moves in a spiral along a cathode surface. There are calculated the coefficients of precipitation equal to the probability of metal emitted from the surface of one electrode and falling onto the surface of the opposite electrode. They are constant close to the central cathode axis, but at the anode approach to the cathode end a coefficient of anode metal precipitation on a cathode decreases, a coefficient of cathode metal precipitation on an anode increases. The rates of anode erosion and cathode weight increase when the mass ratio of eroded substance of anode and cathode increases in the course of one discharge. When this ratio is equal to 5, a coefficient of mass transfer achieves 0.8-0.9 it tells of small substance loss during its transfer between electrodes. The model developed is useful for the parameter estimate of mass transfer between cylindrical electrodes at electrospark processing taking into ac-count their dimensions and paths of anode motion.

Processing Behavior of Electrodes Made with Addition of Nanopowder

The study analyzes the processing behavior of welding electrodes made with addition of nanopowder, and compares them to standard welding electrodes (without addition of nanopowder). The effect of nanopowder of complex composition on the electrode metal transfer process is analyzed as well.

Shunting of the arc current in plasma-arc consumable electrode welding (plasma-MIG welding)

ABSTRACTSpecial features of the process of shunting plasma arc current with a consumable electrode are investigated. The effect of the diameter of the consumable electrode, its visible extension and plasma arc current on the shunting current is determined. The effect of shunting current on the electrode metal transfer and the rate of electrode melting is determined.

Mathematical Formula to Determine Geometrical Dimensions of Electrode Metal Droplets Transferred with Short Circuits

A method is described to determine geometrical dimensions of electrode metal droplets depending on short circuit duration. It provides a quantitative evaluation of the electrode metal transfer and the energy impact on metal parts being welded. It is proved that using inverter power source decreases the size of droplets transferred to the welding pool by 24% in average if compared with a diode power source. It also reduces overheating of the droplets which improves efficiency of transferring chemical elements from the electrode to the weld metal.

Energy Parameters of Weld Formation Process in MIG-MAG Welding

The article presents results of an experimental study and simulation of the effect of welding arc energy characteristics on the nature of electrode metal transfer in MIG-MAG welding. Based on the research results, a method has been developed for determining the coefficient of welding arc plasma flow pressure. The method makes it possible to take into account the dependence of the electrode metal transfer pattern and plasma flow pressure on geometrical dimensions of a welded joint.

Development of the Device for Two-Strip Cladding with Controlled Mechanical Transfer

A two-tape electrodes surfacing device with controlled transfer of electrode metal is proposed. The kinematical scheme and parameters of the process were investigated. It is established that the application of the developed device allows providing a more equable distribution of thermal energy across the width of the tape electrodes and a controlled dropping of liquid metal droplets.

How Dynamic Properties of Inverters Influence Electrode Metal Transfer to the Weld Pool, and Change Structural and Phase Composition of Welded Joints Produced via High Alloyed Electrodes

Covered-electrode arc welding has been currently widely-spread in assembly and maintenance technologies, as soon as it is a reliable tool, which helps get safe permanent joints in critical structural systems applied in Arctic. It is of burning importance to further enhance accuracy in methods which assess the impact of dynamic properties of power supply equipment with various forms of energy conversion on a consumable electrode welding stability and quality. Literature review [1–11] confirms that objectives, aimed at improving critical (in terms of extreme work and low temperatures) metal structures reliability, demand innovative approaches, i.e.:

Effect of Inverter Power Source Characteristics on Welding Stability and Heat Affected Zone Dimensions

The paper presents results the research in the effect of power sources dynamic characteristics on stability of melting and electrode metal transfer to the weld pool shielded metal arc welding. It is proved that when applying inverter-type welding power sources, heat and mass transfer characteristics change, arc gap short-circuit time and drop generation time are reduced. This leads to reduction of weld pool heat content and contraction of the heat-affected zone by 36% in comparison the same parameters obtained using a diode rectifier.

Investigation of the stability of melting and electrode metal transfer in consumable electrode arc welding using power sources with different dynamic characteristics

The results of investigations carried out to study the effect of the dynamic characteristics of power sources on the stability of melting and electrode metal transfer to the weld pool in consumable electrode arc welding are presented. It is shown that when using a new generation of welding inverter power sources the heat and mass characteristics change and this has a decisive effect on the heat content of the weld pool, reduces the level of residual stresses in the heat-affected zone (HAZ) and also increases the susceptibility to reducing the size of structural components in the zone of permanent welded joints.

Dynamic Action of the Shielding Gas Jet Upon the Process of Consumable Electrode Welding

The author considers the gas-dynamic action of the shielding gas jet during consumable electrode welding on the processes in the welding area and properties of the weld joints produced from alloyed high-strength steel 30HGSA. The results of the research on the gas-dynamic action of the jet on the process of consumable electrode welding are provided. It was established that the method of consumable electrode welding with double-jet gas shielding ensures regulated gas dynamics in the welding area and allows controlling the electrode metal transfer, the chemical composition of the weld metal, stabilizing the process of welding and ensures stable high mechanic properties of the weld joints.

Integral self-regulation in arc welding processes

As a result of the development of processes of gas-shielded consumable electrode arc welding with a constant electrode wire feed rate, characterized by different mechanisms of electrode metal transfer and large changes in the arc power with time, this study is carried out to supplement and generalize the concept of self-regulation of different arc welding processes.

Improving Hygienic Characteristics of Coated Electrodes for Welding High-Alloy Steels

The article presents the results of experimental studies showing that the use of an inverter power supply instead of a diode rectifier provides:: fine-droplet electrode metal transfer which reduces generation time by 46% and transfer time by 28%; transfer of alloying elements from welding materials into the weld metal which reduces its loss from the welding line by 6% and the heat affected area by 3%; reducing the emission rate of welding fumes and their components by 23%; reducing specific emission of welding fumes and their components by 23%.

Pulsed arc welding with intermittent spray metal transfer by rectangular pulses

Special features of producing rectangular pulses from welding power sources with inverter transducers for the intermittent spray transfer of electrode metal are investigated. The methods for obtaining the required current pulse parameters ensuring the stability of consumable electrode pulsed arc welding in a mixture of the shielding gases 80% Ar + 20% CO2 are discussed.

Manganese Content Control in Weld Metal During MAG Welding

The influence of the welding current and method of gas shielding in MAG welding on the content of manganese is considered in the paper. Results of study of the welded specimens of steels 45 when applying welding wire of different formulas and different types of gas shielding (traditional shielding and double-jet shielding) are given. It is found that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

Technology Of MIG-MAG Welds Strength Enhancement

A new technology of MIG MAG welding control is developed. Authors introduce use of power AC and pulse feed of welding wire in the arc zone, that downsizes the heat affected zone, stabilizes formation of electrode metal droplets, as external magnetic field's effect on the arc is reduced. Principal criteria for electrode metal transfer control, when powered by AC sources, are specified.

Technology of Ultrasonic Control Of Gas-Shielded Welding Process

A new approach to implementation of electrode metal transfer control under MAG, MIG welding is suggested. The process ensures control of thermal and crystallization processes, stabilizes the time of electrode metal drop formation. The results of the research allow formulating the basic criteria of electrode metal transfer control via ultrasonic exposure, determining the conditions of producing a more equilibrium structure of deposit metal.

Control of the electrode metal transfer by means of the welding current pulse generator

The paper presents a generator of welding current pulses to transfer an electrode metal into the molten pool. A homogeneous artificial line is used to produce near rectangular pulses. The homogeneous artificial line provides the minimum heat input with in the pulse to transfer the electrode metal, and it significantly decreases the impact of disturbances affecting this transfer. The pulse frequency does not exceed 300 Hz, and the duration is 0.6 ÷ 0.9 ms.

Technology of ultrasonic control of gas-shielded welding process

A new approach to implementation of electrode metal transfer control under MAG, MIG welding is suggested. The process ensures control of thermal and crystallization processes, stabilizes the time of electrode metal drop formation. The results of the research allow formulating the basic criteria of electrode metal transfer control via ultrasonic exposure, determining the conditions of producing a more equilibrium structure of deposit metal.