Consumable Electrode Research Articles

Vibration Fatigue Testing Procedure of High Strength MARS 600 Steel Fillet Welds Using Stainless Steel Consumable Electrode

Implementation of high strength steels in welded structural designs in the automotive, defence and construction industries is constantly increasing. Prolonged usage of such structures requires deep understanding of welded joint fatigue as well as a reliable and feasible life estimation methods development. Conventional fatigue testing methods often require costly, expensive in maintenance, high loading capacity equipment. They are also commonly restricted to specific specimen geometry and are time consuming due to the limit of a single specimen per test setup. This work presents high cycle fatigue (HCF) testing of high strength MARS 600 welded steel using a quick, simple and efficient resonance fatigue testing (RFT) method. The specimen is a simple cantilever fillet welded to a base plate using austenitic stainless steel 307L consumable electrode. Electrodynamic shaker is used for harmonic base excitation at a constant operating frequency. Several specimens welded to the common base are tested simultaneously, allowing completion of a high number of cycles and statistics in a relatively short time period. A hybrid, practical research approach combining experimental, finite element analysis (FEA), numerical and analytical calculations is presented. Fracture mechanics approach for fatigue life assessment is implemented. Crack growth calculation is based on the Paris - Erdogan law. Reduction in structural integrity due to crack propagation causes a reduction in natural frequency and transmissibility. The change in gain is evaluated via the open crack FEA model and integrated into the crack propagation algorithm. Resonance search, track and dwell module (RSTD) for maintaining constant gain throughout the test is not required. Fatigue life Wohler (SN) curve is constructed. Standard weld fatigue data is often provided for direct loading (tensile stress) and for different stress ratio (R) values. Corrections for mean stress and loading application are required. Current fully reversed (R = -1), indirect loading (bending stress) test results may be readily applied for random vibration fatigue analyses post processing. As expected, actual fatigue life results are higher compared to standard design curves, implying correctness of the manufacturing welding process of examined specimens. The presented procedure is of interest for research as well as for industrial welding processes testing, optimization and qualification.

Electrochemical Reduction of K2MoO4–Fe2O3 Binary Melts Using a Consumable Steel Electrode to Produce Ferromolybdenum Alloys

Electrochemical Reduction of K2MoO4–Fe2O3 Binary Melts Using a Consumable Steel Electrode to Produce Ferromolybdenum Alloys

Effect of Different Power Supply Modes on Inclusion in 304L Stainless Steel Electroslag Ingot

The use of low frequency or DC (i.e., direct current) operation in the electroslag remelting process may lead to the electrolysis of some oxides in the slag pool, which will adversely affect the cleanliness of the electroslag ingot. In order to confirm this view, the effect of different power supply modes on the oxygen content and inclusions in electroslag ingot has been studied by adopting the self-designed electroslag remelting furnace as experimental equipment. The pulse heating inert gas fusion-infra-red absorption method is used for analyzing oxygen content. The analysis of non-metallic inclusion is conducted using an automatic SEM (i.e., scanning electron microscope) made by the American ASPEX Company, where the inclusion type and the inclusion size are determined. Results show that the oxygen content in the electroslag ingot increase significantly compared with that in the consumable metal electrode, whether under the frequency of 50 Hz, low-frequency, or DC. When DCSP (i.e., the consumable electrode is connected to the cathode of the DC power supply), DCRP (i.e., the consumable electrode is connected to the anode of the DC power supply), 2 Hz, 10 Hz, and 50 Hz power supply modes are adopted, the oxygen content in electroslag ingot is 155.3 ppm, 100.4 ppm, 75.8 ppm, 66.3 ppm, and 43.2 ppm respectively. With the increase in oxygen content, the number of inclusions in electroslag ingots increases significantly, and the increased inclusions are mainly Al2O3 inclusions. Regardless of the power supply mode, the largest diameter of inclusion is less than 20 μm. The electrolysis of Al2O3 is the direct reason for the increase in oxygen in the electroslag ingot when CaF2-Al2O3 slag is used. With the decrease in frequency, the electrolysis trend increases, and the oxygen content and the number of inclusions also increase. However, most of the inclusions are regenerated with the decrease in metal pool temperature and solidification, so the size is fine.

A new understanding of laser-arc plasma interaction of hybrid welding based on arc layering behaviors

Current studies of laser-arc plasma interaction have been based on a single-layer structure but ignored the layering behaviors of the metal inert gas (MIG) arc, resulting in a lack of insight into some phenomena of laser-MIG hybrid welding. Here, the effects of laser power on the double-layer MIG composed of an outer plasma layer and a core metal vapor layer were investigated. The results showed that the emergence of arc layering was delayed by laser-arc plasma interaction, the time of which reached the maximum of 0.83 ms after the laser power increased to 4 kW, 1.66 times that of pure arc. Importantly, the outer layer was expanded, and the core layer was constricted by laser power, which was different from the previous argument that the arc was only compressed. An equivalent parallel circuit was proposed to reveal the current redistribution between the outer and core layers, and then the electromagnetic force was calculated to discuss the mechanism. Finally, the space-time evolution of the arc expansion and constriction phenomenon was described. These new findings explained the weld shape variations more reasonably and demonstrated the necessity to consider arc layering during laser-arc hybrid processes with a consumable electrode.

REPAIR TECHNOLOGY OF PRODUCT PIPELINES OPERATED IN A HYDROGEN SULFIDE ENVIRONMENT

Introduction. The article discusses the improved repair technologies of pipeline material saturated with hydrogen sulfide, which should replace conventional repair methods that ignore operational features in a hydrogen sulfide environment.The aim of this work is to develop a technology for repairing pipelines operated in a hydrogen sulfide environment by manual arc welding using a consumable electrode.Materials and methods. Full-scale experiments were carried out to achieve the goals. A section of an industrial pipeline was selected as a test sample, whose service life in a hydrogen sulfide environment at the hydrocracking unit of an oil refinery equals about 10 years. Degassing, i.e., the removal of diffusion atomic hydrogen from the metal in the repairing area, was carried out using electric heating devices. The surfacing of the pipe edges using a layer of austenitic or ferritic metal was carried out by manual arc welding.Results. The developed technology for repairing pipelines operated in a hydrogen sulfide environment by manual arc welding using a consumable electrode involves degassing and surfacing the edges with metal having the same composition as the parent material. Here, the positive effect of surfacing lies in the fine distribution of non-metallic inclusions in the remolten metal and a favorable change in their shape and chemical composition.Conclusions. The efficiency of the repair technology of industrial pipelines using welding is achieved by taking into account the properties of a transported product and its influence on the welding process. When developing the welding technology of industrial pipelines operated in the hydrogen sulfide environment, such basic measures as preliminary degassing of pipe metal, preliminary surfacing, and heat treatment of pipe edges are substantiated.

Electroslag heating and additional melt feed of steel ingots of semi-continuous casting

The issues related to the continuous compensation of metal shrinkage during its crystallization are studied. Based on the evaluation of ways to reduce the size of the shrinkage shell, aimed at maintaining the liquid phase for a long time, the most effective ways to reduce the size of the shrinkage shell and reduce the head trim are selected. The influence of electroslag heating and recharge technology on the length of the shrinkage shell and the quality of the metal of the sub-shrinkage area of semi-continuously cast ingots has been studied. The study was carried out on ingots with a diameter of 500 mm weighing 3.5 tons of carbon and alloy steels. The installation consisted of 3 electrodes with a diameter of 75–100 mm, connected to the transformer TSH-3000-3. The transformer power was 570 kVA, the current per phase was 1000–3000 A, the voltage on the electrodes was 40–60 V. Temperature measurements were carried out in the copper sleeve of the mold. For comparison, the temperatures in the walls of the mold were recorded during the cooling of the ingot in the mold without heating. The cooling curves showed that the process of electroslag heating does not cause overheating of the mold walls. This is explained by the appearance of a side metal crust in the upper part of the ingot, which does not melt with liquid slag and protects the walls of the mold. The surface of the ingots had no visible defects (crust inversions, film and slag inclusions). Additional surface treatment (stripping, stripping) was not required. The macrostructure of the ingots is dense, without visible defects, including in the axial zone. Sulfur liquation on sulfur prints according to Bauman was not detected. Electroslag heating had a significant impact on the length and shape of the shrinkage shell. The results obtained show that electroslag heating with graphite electrodes, feeding with consumable steel electrodes of the same composition with the resulting ingot and electroslag casting of steel can improve the structure, density and chemical homogeneity of cast metal, reduce the content of non-metallic and gas inclusions and significantly increase the yield of usable compared to conventional casting.

Computer aided engineering of technological features of double-arc surfacing with current-carrying filler wire of contact surfaces of centrifugal pump

A technology for restoring of the contact surfaces of a centrifugal sectional pump is developed and technological requirements for the necessary equipment for its practical implementation are formulated on the basis of computer aided engineering of the technological capabilities of double-arc surfacing with a consumable electrode with a current-carrying filler wire. It is shown that the use of the proposed technology and robotic equipment for its implementation makes it possible to increase the productivity of surfacing by 1.8—2 times and provides an acceptable content of the substrate material in the deposited layer.

Simulation of the distribution of temperature, stresses and deformations during splined shafts hardfacing

This article describes the process of modeling the restoration operations of the destroyed segment of the spline and its complete restoration using modern methods, such as hardfacing in a protective gas environment with a consumable electrode. The ANSYS Workbench 19.2 software with an additional Welding Distortion and Moving Heat Source extension was used to simulate the process of hardfacing a damaged surface. The thermomechanical behavior of the deposited layer on the outer surface of the splined shaft is analysed. Dependences of the value of temperature fields on the parameters of the hardfacing mode in one and two passes depending on time are established. Dependences of residual stresses (0.413-239 MPa) and deformations (0.02-0.23 mm) in the process of semi-automatic hardfacing are determined. Experimental studies of samples during hardfacing were carried out for comparison with the geometry of the weld during modeling. The simulation results are in good agreement with the experimental data.

The formation of alloy based on Al-Ti-B system by electroslag process involving dispersed engineering waste

In this article presents technological process of manufacturing Al-Ti-B rod master alloy by electroslag casting is proposed and investigated. Aluminum alloy chip waste of a grade AK7, commercial titanium of a grade VT1-00 and amorphous boron of a grade A were used as starting materials. The consumable electrode is a product in the form of a rod obtained by mouthpiece pressing of a mixture of crushed starting materials in a mass ratio of AK7 : VT1-00 : amorphous boron = 97:2:1. According to the proposed technology and the ratio of starting materials in the charge composition, an experimental bar material of the Al-Ti-B ligature was obtained, electron microscopic, micro-X-ray spectral studies, the stereometric analysis of the structure which showed the priority interaction of titanium with boron.

STUDY ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF IS2062 BY ARC WELDING

Quality and efficiency assume vital part in the present assembling Industry. Presently multi day's because of firm and vicious focused economic situation in assembling enterprises. The principle goal of ventures uncover with creating better quality item at least cost and increment profitability. In the present research venture an endeavor is made to comprehend the impact of Arc welding. It is an arc welding process that habits a non consumable tungsten electrode to produce the weld. In an Arc welding, a thin layer of activated flux is brushed on to the surface of the Mild steel IS 2062 joint to be welded. Arc welding parameters like welding current, welding speed , V-Groove Angle ,that are effects on responsive Mechanical properties like tensile strength, impact strength, Creep strength, Micro Hardness, and corrosion. The result will be validated by using a computational tool. Microstructure will be examined by SEM (Scanning electron microscope) and HRTEM (high Resolution tungsten electron microscope)

Computer modeling of the process of siphon casting of a large metal cylindrical ingot

Electroslag remelting is one of the main ways to obtain high-quality large ingots from special steels and alloys, and in particular for the needs of power engineering. Casting in a mold is the most common way to obtain large-sized consumable electrodes for electroslag remelting. Computer modeling was carried out to determine the rational parameters of the process of casting large cylindrical ingots by the uphill casting. This paper presents the simulation results of the movement of liquid metal flows during the filling of a mold with liquid metal and the process of forming a crust of solid metal at that time under the conditions of the uphill casting of a round steel ingot with a diameter of 1 m with a height-to-diameter ratio of 6.5 and a mass of about 40 tons. Analysis of the results of computer simulation shows that in the bath of liquid metal in the mold there is a non-stationary hydrodynamic picture, which changes as the internal volume of the caster is filled with liquid metal. Solidification of the metal begins already at the initial stage of filling the mold. However, under the influence of liquid metal flows, the formation of a crust of solidified metal occurs unevenly due to the uneven distribution of the heat flow from the liquid-metal bath around the perimeter and height of the mold wall, which creates conditions for the hot surface cracks occurrence. To prevent the formation of surface defects, it is recommended to take measures to stabilize the upward flow of liquid metal. The effect of mold preheating on the intensity of metal solidification during the filling of the mold with liquid metal was also investigated. Preheating reduces the amount of solid phase formed during the filling of the mold with liquid metal. The most significant inhibition of the formation of a solid phase with a decrease in the solidified metal volume fraction of 40 % is observed under the condition of preheating the mold wall to at least 550–600 °C.

Visual sensing and quality control in plasma MIG welding

By generating a complementary effect of each weld in the welding process, a hybrid welding can improve the welding efficiency while ensuring the welding quality. The combination of plasma arc welding (PAW) with high current density and metal inert gas (MIG) welding utilizing consumable electrodes is available to perform one-pass welding for the thick plate. The plasma torch works for keyhole welding with deep penetration, and the MIG torch works for a build-up welding to form a surface bead. However, due to the complexity and particularity of the two-electrode system, it is still difficult to achieve a high-quality automatic welding. In this study, the authors have observed the weld zone with a complementary metal oxide semiconductor (CMOS) camera, and analyzed the regulation of image features changing with the torch position. Control strategy of the welding torch and image processing to realize the seam tracking and standoff have been proposed. Utilizing a high-speed video camera, system configuration and welding conditions have been determined with the welding images of the arc behavior and droplet transfer. The authors have investigated the corresponding welding conditions when the welding defects occurred. In addition, we have modified the power source with an invertor control and designed a characteristic curve for the power source to stabilize welding conditions and enhance the MIG arc length self-regulation. The performance of welding system for the seam tracking and standoff control is effective in the real-time welding experiment. The power source with an invertor control and the designed characteristic curve can optimize the welding conditions and acquire good welding results. The study has achieved a high-quality welding under the condition of automatic plasma MIG welding.

Fume emissions by electric arc during gas metal arc welding

The influence of welding arc regime on the welding fumes formation is studied by numerical modeling via description of separate processes inside the space charge regions near electrodes in the welding arc with consumable electrode. The modeling comprises the calculation of temperature profiles for electrons and heavy component, calculation of space distribution of gas components’ number densities, of gas particles’ mean free pathes, of electric potential and field, calculation of the heat transfer from electrode wire (anode) to molten pool (cathode). The formation of high temperature metal vapor from molten pool to environment as a function of arc current is demonstrated. The nucleation in the plasma of welding fumes is considered with taken into account ionization of vapor atoms via their interaction with nucleus surface. The growth of nucleus droplets via vapor condensation and coalescence is calculated. The coagulation of solid primary particles for various values of welding current is calculated and inhalable particle size distribution is demonstrated.

Evolution and Formation of Non-Metallic Inclusions during Electroslag Remelting of Ce-Bearing 15Cr-22Ni-1Nb Austenitic Heat-Resistant Steel

The evolution of inclusions in austenitic heat-resistant steel with different Ce content during protective argon gas atmosphere electroslag remelting (ESR) was studied. All oxide inclusions in the Ce-free consumable electrode are MgO·Al2O3. A part of these MgO·Al2O3 inclusions was removed before metal droplets entered the liquid metal pool during the ESR. The soluble oxygen (arising from the reoxidation) reacted with soluble aluminum, calcium, and magnesium in liquid steel to form MgO·Al2O3 and CaO–Al2O3 inclusions in liquid steel. All oxide inclusions in the electrode with 0.016 mass% Ce are Ce2O2S. A portion of these Ce2O2S inclusions was dissociated into soluble oxygen, cerium, and sulfur in liquid steel during the ESR process, whereas the others were removed by absorbing them into molten slag. The oxide inclusions in the liquid metal pool and remelted ingot were Ce2O3, CeAlO3, and Ce2O2S. The CeAlO3 and Ce2O3 inclusions were reoxidation products formed by the chemical reaction between the soluble oxygen, soluble aluminum, and cerium. The oxide inclusions in the electrode with 0.300 mass% Ce are CeS and Ce2O2S. These CeS inclusions were removed by molten slag adsorption during the ESR. A part of these Ce2O2S inclusions was removed by slag adsorption, and the remaining entered into the liquid metal pool. The oxide inclusions in the liquid metal pool and the ingot were Ce2O3 and Ce2O2S. The Ce2O3 inclusions were formed through the chemical reaction between the soluble oxygen and cerium in the liquid metal pool. The Ce2O2S inclusions in the liquid pool originate from reoxidation products during the ESR process and the relics from the electrode.

Experimental evaluation of longitudinal tensile properties of ferritic stainless-steel weldment joined by metal inert gas, pulse metal inert gas, and tungsten inert gas welding

In this work, ferritic stainless steel (FSS) weldments were prepared by tungsten inert gas (TIG), metal inert gas (MIG), and pulsed-MIG welding. Pure argon and a mixture of argon + 2% oxygen were utilized as shielding gas in each type of welding. The FSS (ER430) and austenitic stainless steel (ASS) (ER309L) wires were used as filler consumable wires during all the three types of welding. The effects of varying welding processes, shielding gases, and consumable electrodes on the longitudinal tensile properties of weldments were investigated. The universal tensile testing machine was used to evaluate longitudinal ultimate tensile strength and percentage elongation experimentally in each case. The maximum tensile strength of FSS weldment was obtained in the case of (Ar + 2% O2) mixture of shielding gas and ASS filler wire in each welding process. Heat treatment was also carried out for samples prepared by MIG and TIG welding. The reduction in tensile strength and enhancement in percentage elongation was observed for both MIG and TIG welding after heat treatment.

Explicitly controlling electrical current density overpowers the kinetics of the chlorine evolution reaction and increases the hydrogen production during seawater electrolysis

The chlorine evolving reaction (CER) subdues the oxygen evolving reaction (OER) during seawater electrolysis, and impedes hydrogen production without generating harmful chlorine byproducts. We describe a new approach to suppressing CER and increasing the hydrogen production rate by highlighting its distinctive features: using electrical current densities Jc > 10 A cm−2 that are much larger than the 1 A cm−2 currents conventionally employed; and using consumable graphite rod-shaped electrodes. Our approach creates a practical means for reaching an electrochemical regime where CER is drastically reduced and hydrogen production is substantially increased. Finite element modeling indicates the rapid reduction in CER is associated with establishing a steep gradient in the electric field between the electrodes. Our study suggests that explicitly elevating Jc to more than 10 A cm−2 creates opportunities for creating hydrogen for use in large-scale and industrial applications by reducing CER to negligible levels – an environmental incentive – while increasing the OER and hydrogen production – an economic incentive.

The effect of process parameters on microstructure and corrosion behavior of AISI 4140 steel modified by pulse plasma treatment

The pulse plasma system is a surface modification method applied to steel samples. In the present study, the effect of the nozzle distance and pulse number parameters were investigated on the modification process. AISI 4140 steel was preferred as the substrate for modification. In this system, the battery capacity and voltage were constant, and, were selected as 800 mF and 3000 V, respectively. The AISI 4140 steel samples were modified by applying 5, 10, and 15 pulses with 40, 50 and 60 mm nozzle distance. The molybdenum consumable electrode was used during the process. The modified surfaces were examined by optical and scanning electron microscope (SEM) and analyzed by X-ray diffractometer (XRD). Vickers microhardness on the cross-section surface of the samples was measured under a load of 50 g for 15 s. Finally, the specimens were exposed to corrosion in 0.5 M NaCl solution. Corrosion tests were realized using the potentiodynamic polarization method. A modified layer on the steel was determined to consist of two layers, the compound layer and the diffusion layer. It was observed that the structure and thickness of the modified layer affect by pulse number and nozzle distance. New phases such as Fe2N, FeN, MoN, and γ-Fe in the modified layer have occurred. The hardness value of the treated sample has risen about 4-5 times than the untreated, depending on applied process parameters. In general, the pulse plasma treatment has improved the corrosion resistance of treated samples. It was observed that while intergranular corrosion has formed on the unmodified surface, pitting corrosion has appeared on the unmodified surfaces.

Influence of technological parameters on nitriding rate in obtaining metal powders by plasma centrifugal spraying

Increase in metal operational properties is ensured by introduction of a certain set and amount of alloying elements into it. These elements include nitrogen, the interest in which is constantly growing. As many works have shown, nitriding with gaseous nitrogen is used, among other things, in plasma-arc remelting. The data is given on metal alloying with nitrogen at the stage of obtaining granules and powders. However, the latter process requires further study. The process of obtaining nitrogen-containing metal microgranules from EP741NP alloy by plasma centrifugal spraying was studied in this work. Metal powders are obtained by melting the end of a rotating workpiece with a stream of ionized gas (mixture of gases). The technology makes it possible to obtain nitrogen-alloyed fine metal powders of multicomponent spherical alloys with a minimum number of satellites that do not differ in size and chemical composition. Investigation of the nitriding rate is of great interest, especially in the production of powder metal. One of the parameters that affect the degree of metal saturation with nitrogen is time spent by liquid melt under nitrogen-containing plasma and crystallization time of the metal drop. The paper presents a technique that allows one to quantify the role of these parameters on the absorption of nitrogen by the metal during powder production. It is known that the kinetic parameters of the nitriding process are determined by the contact area of ​​two metal – gas phases. In the case of obtaining a powder, this parameter depends on the size of a powder speak. In this connection, the paper presents a calculation method that allows estimating the average fractional composition of metal powders depending on a number of technological factors. The obtained values ​​were compared with the data of semi-industrial heats. It is shown that the fractional composition of microgranules depends on the rotation speed and diameter of the workpiece being remelted, the density of the alloy, and the force of surface tension. It was established that with an increase in the rotation frequency of the consumable electrode, it is possible to achieve a decrease in the fineness of metal powders.

Microstructure and Mechanical Properties of Joints Depending on the Process Used.

Today, numerous design solutions require joining thin-walled sheets or profiles as the traditional methods of welding with a consumable electrode in gas shielding, most often used in production processes, do not work well. The reason for this is that a large amount of heat is supplied to the joint, causing numerous welding deformations, defects, and incompatibilities. Moreover, the visual aspect of the connections made more and more often plays an equally crucial role. Therefore, it is important to look for solutions and compare different joining processes in order to achieve production criteria. The paper compares the properties of a 1.5 mm thick steel sheet joined by the manual and robotic MAG 135 and 138 welding process, manual and robotic laser welding, CMT welding with the use of solid or flux-cored wire, and butt welding. The macro- and microstructure, as well as the microhardness distribution of individual regions of the joints, were analyzed depending on the type of joining technology used. Furthermore, the mechanical properties of individual zones of joints were investigated with the use of a digital image correlation system. On the basis of the obtained test results, it was found that the joints made by the processes of manual laser welding and butt welding were characterized by a very regular weld shape, the smallest joint width, and greater grain refinement compared to other analyzed processes. Moreover, this method was characterized by the narrowest zone of hardness increase, only 3 mm, compared to, e.g., a joint made in the process of robotic welding CMT, for which this zone was more than twice as wide. Furthermore, the heat-affected zone for the joints made in this way, in relation to the welds produced by the MAG 135/138 method, was, respectively, 2 and 2.7 times smaller.

PH-sensitive thermally regenerative cell (pH-TRC) with circulating hydrogen for long discharging time and high-power output

Thermally Regenerative Cell (TRC) is a recently proposed promising approach for converting low-grade waste heat into electricity, but the power density and discharging time are limited by the loss of electrode active material and unoptimized cell design. By replacing the early consumable electrode with H2/H+ catalytic electrode and rationally improving the cell design, here we report an advanced pH-sensitive thermally regenerative cell (pH-TRC) with circulating hydrogen to achieve both long discharging time and high-power output. Between the H2/H+ catalytic electrodes we have flowing anolyte and catholyte with different pH values, which can be neutralized through discharging reactions and then thermally regenerated to reset the initial state. With this new design, a favorable peak power density of 5.296 W m−2 is obtained. More importantly, an incredibly long discharging time over 40 h enables the powering of a smart phone in comparison to only hundreds-of-seconds discharging time of previous TRC.