Electroslag Process Research Articles

RESTORATION OF LARGE MODULAR TEETH OF BALL MILL GEARS BY ELECTRO-SLAG SURFACE

This article is devoted to researching the possibility of restoring straight-toothed large-module gears by electro-slag surfacing of individual defective teeth. During the work, an installation was designed and manufactured to restore gears that do not require further machining. A comparative analysis of the proposed technology with the traditional surfacing technique was carried out, paying attention to variables such as the composition of the surfacing material used, process parameters, stabilization of the electro-slag process, and ensuring the geometric dimensions and profile of the tooth. The study results demonstrate that the proposed technology provides higher hardness and wear resistance of remanufactured parts compared to traditional methods.

Effect of slag composition and current density on ingot cleanliness during low-frequency/DC electroslag process

Effect of slag composition and current density on ingot cleanliness during low-frequency/DC electroslag process

Technology and hardware design of remelting cast iron shavings by electroslag process

The article describes the technology and its hardware design for the processing of cast iron shavings. One of the pressing problems of modern machine-building enterprises is the handling of shaving waste, which occurs during the machining of various kinds of metal workpieces and parts. A distinctive feature of the present development is an integrated approach to this problem, which allows for the continuous processing of cast iron shavings in their original unprepared state in an aggregate from a combination of two components, in which the discussed machine-building shaving waste is heated in a solid state to a temperature of 750–850 ºС with simultaneous release from moisture, coolant, iron oxides (in the first component of the installation) and is transferred to a liquid aggregation state in a barium chloride melt with addition of silicon carbide (in the second component). Natural gas and electrical energy of 0.010–0.012 m3 and 0.75–0.80 kWh, respectively, per 1 kg of the resulting liquid metal are spent on carrying out the described technological operations. As a result of the study of the mode of continuous processing of cast iron shavings at the experimental plant, statistically significant indicators were obtained that characterize its productivity (about 400 kg of liquid metal per hour), the change in the mass and chemical composition of the material being remelted with the achievement of low losses for waste (2.2% wt.) and the preservation of the main alloying element of cast iron - carbon. The purpose of this study is to develop a technology and its hardware design for processing of cast iron shavings with a minimum percentage of waste.

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.

Microstructure and corrosion properties of the AISI 904L weld cladding obtained by the electro slag process

The AISI 904L steel is a superaustenitic stainless steel, which presents a good combination of properties like high strength, weldability, and good corrosion resistance. Despite its wide use in several industrial segments, the literature reporting the performance of claddings deposited with this alloy to improve the corrosion performance of equipment is limited. Based on this scenario, this work evaluates the microstructure and corrosion properties of the AISI 904L steel weld cladding obtained by the electroslag welding (ESW) deposited on a carbon steel ASTM A516 Grade 70. Single layer cladding was deposited on 50 × 400 × 400 mm steel plates with average welding energy of 11.7 kJ/mm to obtain the minimum thickness required. After welding, metallographic examination and corrosion tests were performed on samples removed at 1 and 3 mm parallel to the fusion line. Metallographic characterization was performed by optical and scanning electron microscopy. Cyclic polarization tests in 3.5% NaCl solution were performed at the same positions as the metallographic examinations. The results showed that the austenitic microstructure presenting a low volume fraction of secondary phases provided suitable corrosion results for all conditions studied. It evidences that single layer weld overlays obtained with the AISI 904L steel deposited by the ESW process may be considered an adequate alternative for overlay welding with reduced thicknesses because good results were observed at only 1.0 mm from the fusion line, and this could represent a significant cost reduction.

Gas Atomization of X6CrNiTi18-10 Stainless Steel Powder for Selective Laser Melting Technology

Powders of X6CrNiTi18-10 stainless steel were fabricated from original workpieces of different grade by gas atomization method. It was found that it is necessary to use argon as a gas for gas atomization of X6CrNiTi18-10 steel, since the use of nitrogen leads to the formation of its compounds, namely, titanium nitride. It is shown that all used workpieces – electric arc, electric slag and vacuum arc refinement – allow one to obtain powders suitable for further utilization in selective laser melting technology of 3D printing. The main physicochemical and technological properties of the obtained powders have been investigated. Changes in the chemical composition and quality of the powders are not significant within the X6CrNiTi18-10 grade. The 0...20 μm fraction of powders does not have fluidity, and thus cannot be used for additive technologies. The fraction 20...63 μm have suitable rheological properties for additive technologies and may be used in selective laser melting (SLM) process. The yield of target fraction 20 ... 63 microns was ≈45%. The fraction 63...120 μm may be used for the direct metal deposition (DMD) additive technology. Considering the economic aspect of the technology, it is preferable to use original workpieces of X6CrNiTi18-10 steel produced by electric arc or electroslag process, since the market price of vacuum arc steel is significantly higher. The fraction of ferrite phase in the powder increases with a decrease of particle size of the resulting powder and is lower comparing to the original workpiece. In the future, for a detailed study of the technological properties, it is planned to grow samples from each type of the obtained powders on installation for selective laser melting and direct laser deposition to determine the physical and mechanical properties of fabricated samples (tensile and impact bending tests) and carry out metallographic studies.

The Sectors Workpieces and Drum Reel’s Die Cubes Electroslag Casting with Exothermic Electrical Conductive Fluxes

It has been established that the developed method of manufacturing workpieces for the sectors of the drums of X20CrMoWV3 steel reel’s and die cubes from X5CrNiMo steel using a solid start and exothermic flux significantly reduces the complexity of their manufacture. The cast reel’s drum sectors workpieces and die cubes, obtained by the electroslag remelting (ESR) method, had a smooth surface without corrugations, sinkers, and slag inclusions. Heat treatment provides the required mechanical properties and the absence of flocs in the cast electroslag metal. An effective way to increase the performance of electroslag processes is using the exothermic flux, which contain scale, ferroalloys, aluminum powder and standard flux (welding flux ISO 14174 – S F AF3, etc.) in quantities sufficient for the exothermic reactions to occur, which ensures the generation of additional heat in the starting period of electroslag processes and contributes to the accelerated induction of the slag bath of the required volume at the “solid” start both monofilar and bifilar schemes of conducting the process instead of the “liquid” start. Electroslag processes using an exothermic alloyed flux on a “hard” start allow to obtain (compared to existing methods of slag bath formation) an increasing in the output of a suitable metal 2...10 %; saving on melting 1 kg of standard flux 1.2...1.4 kW h; reducing of the starting time of the ESR process to 25 %.

Mass Transfer in Electroslag Processes with Consumable Electrode and Liquid Metal

Experimental and numerical comparisons of mass transfer processes during the electroslag remelting with consumable electrode (ESR) and electroslag refining with liquid metal (ESR LM) showed their identical refining capacity, despite the smaller both the slag–metal contact surface (twice) and metal overheat (by 70–95 K) in the latter case. As revealed, due to effect of metal movement inside the liquid metal drop, it moves in liquid slag faster than a solid particle of the same diameter. Under comparable conditions, it is experimentally confirmed that desulphurization at the ESR takes place mainly on the contact surface between the slag and metal baths, but not in the liquid metal film at the tip of a consumable electrode.

Titanium production by magnesium thermal reduction in the electroslag process

Titanium is widely used in specific applications due to its high strength, low density and good chemical stability. Despite it is one of the most abundant elements in the earth’s crust, it is very expensive, because production of pure metallic titanium is very complex. Kroll process is the way how most of the titanium is produced nowadays. Shortages of this process are that it is batch process and it is very energy exhaustive, because titanium sponge material after reduction reaction needs complex post processing to isolate pure titanium. In this work we describe and experimentally investigate technology for Ti production from titanium tetrachloride using combined Kroll and electroslag process. Such process allows to achieve better reaction product separation by molten slag and process can potentially be continuous, thus technological process to produce metallic titanium can be significantly shortened.

Investigation of the melting point of the slags used in the processes of special electrometallurgy

The development of the metallurgical industry of Ukraine to a large extent depends on the export of high quality steel, which is smelted by means of special electrometallurgy. The quality of the metal produced in process of electroslag remelting is determined by the technological properties of the slags used. In electroslag processes, the slag, which is a source of heat, performs a number of other important functions: refines metal from non-metallic inclusions, gases and harmful impurities, protects the liquid metal from interaction with the atmosphere, provides a good quality surface of the ingot. In order to use the slags of rational chemical composition, experimental studies of melting intervals were performed by optical and contact methods. Optical studies were performed at the high-temperature heating microscope MNO-2, manufactured by Carl Zeiss. The microscope was upgraded: the internal galvanometer, which introduced errors into measurement, was replaced by an external galvanometer, which was connected with platinum-platinum thermocouple. The process of slags melting was shot with a digital camera. When applying the contact method, crushed slag was put into a crucible of boron nitride and slowly heated in the furnace (0,15-0,30°С/с). The state of the slag in the crucible was evaluated by probing with a tungsten rod. The results of the experiment showed that the melting point of the slags (fluxes) during the heating of a large mass of slag in the furnace is more than the real temperature. The results of optical measurements using the microscope MNO-2 are more reliable. The experimental results obtained are in line with the literature data for fluxes with chemical composition close to the studied ones. The results of the performed research make it possible for us to recommend for industrial use the fluxes AN-14, AN-15, AN-15M, which, in addition, contain a small amount of harmful fluoride

Determination of Nitrogen Content in the Slags of CaO — Al2O3 System by Kjeldahl Method

Due to the expansion of the nomenclature of steel grades in the industry and the development of new special alloys with increased strength and corrosion-resistant properties, both in the metallurgical industry and in welding, researchers are very interested in the dissolution of nitrogen in metals and slag. Gas permeability of slag is one of the reasons for the appearance of gases in both the base metal and the weld metal. It is determined by two properties: solubility and mass transfer of gases in slag. In addition, in real conditions, the process of dissolving gases in slag is influenced by the transmission of gases by convection and the initial content of gases in the slag. The transfer of gases to the metal through slag is observed mainly in electroslag processes and welding under flux when there is no direct contact of molten metal with a gas phase. To evaluate the nitrogen permeability of the slag and the mechanism of nitrogen solubility in the high alloys it is necessary to have a reliable, highly sensitive and economical method of gas analysis of nitrogen in metals and slags.
 A review of nitrogen determination methods in steels is presented. The method of analysis of nitrogen in slags of the CaO — АL2O3 system by the Kjeldahl method was tested. The results of the analysis of slag compositions of the CaO — АL2O3 system allowed us to conclude that it is possible to use the Kjeldahl method (determination of nitrogen content in steels) for the determination of nitrogen content in slags. This technique and installation can be recommended for use by metallurgists and welders as a reliable, simple and inexpensive method for nitrogen content analysis in metals and slags.

Receiving billets of shut valve from steel 08Х18Н10Т method of electroslag smelting with additional heating of the consumable electrode (ESS + AH)

Purpose. To obtain by the method of electroslag smelting with additional plasma-arc heating of the consumable electrode (ESS + AH) billet of valve from steel 08Х18Н10Т. Determine the process parameters and examine the quality of the cast metal billets of valve.Research methods. Electronic fixation of melting technological parameters (current, voltage, electrode feed rate, power consumption). Macro and microanalysis of the casting structure. Metallographic method for determining the volume fraction of non-metallic inclusions. Mechanical testing.Results. It was established that additional plasma-arc heating of the consumable electrode during electroslag smelting can increase the allowable fusion rate of the ingot to 20 %, while reducing the specific power consumption by 15–17 %.The quality of the metal obtained billet of valve fully meets the requirements of GOST 5632-72, GOST 25054-81.Scientific novelty. For the first time, the possibility of improving the technical and economic indicators of the electroslag process while maintaining the quality properties of the metal is shown. The way ESS + AH is protected by copyright certificate.Practical meaning. Based on the data provided in the article, it is possible significantly expand the scope of application of ESS + AH technology to obtain a wide range of parts.

Formation of metal pool in current-supplying mould at electroslag process

Formation of metal pool in current-supplying mould at electroslag process

. Формирование металлической ванны при электрошлаковом процессе в токоподводящем кристаллизаторе

. Формирование металлической ванны при электрошлаковом процессе в токоподводящем кристаллизаторе

Improving a resource­saving surfacing technology using two ribbon electrodes with a controlled transfer of electrode's metal

This paper reports results of research into a resource-saving technology of surfacing with two ribbon electrodes with a controlled transfer of the electrode's metal from the end sides of ribbon electrodes and with an adjustable ratio between the ribbon electrodes' feed speed. To implement the proposed technology of surfacing, we designed a device that makes it possible to change the ratio between feed speeds of the first and second electrodes in a wide range. That provides for a controlled heat-mass transfer to the welding bath. As well as, accordingly, a controlled fusion of ribbon electrodes and the distribution of thermal energy throughout a welding bath. This makes it possible to improve quality of the surfaced products using a simple and reliable resource-saving device. A given design makes it possible to optimize parameters for a pulsed mechanical transfer and prevent the deformation of ribbon electrodes, to ensure an alternating reciprocation motion of the ribbon electrodes' end sides at optimal frequency and amplitude. That provides for the optimal size of the surfaced bead while making it possible to reduce the consumption of an electrode's metal for loss and overheating, and, accordingly, the consumption of energy for melting, as well as ensure a resource saving technology of surfacing. The process of surfacing with two electrodes, even when using fluxes recommended for arc welding, occurs partially similar to the electroslag process, because a certain percentage of current is shunted by the molten slag. This helps reduce the depth of welding and lowers the share of the base metal in the surfaced metal. The main advantage of surfacing with two ribbon electrodes is obtaining the surfaced metal with the required chemical composition as early as in the first or second layer, in contrast to the single-electrode surfacing where it is necessary to apply from 3 to 5 layers. Results of research into the influence of oscillation frequency of ribbon electrodes have revealed that the maximum increase in a melting coefficient occurs at oscillation frequency in the range of 45‒55 Hz regardless of other mode parameters

Electroslag process for better titanium deposition morphology

Most common process for titanium production nowadays is Kroll process. This process has several drawbacks. Process is cyclical, and titanium comes out in sponge like form. This means that process is long, reaction is uncontrollable and requires post-processing of titanium sponge, which is energy consuming. In this work we present the idea to use Kroll process combined with electroslag process to produce titanium in continuous, more efficient process. Main idea is to use heated reactor where the initial reaction products (titanium tetrachloride and magnesium) are injected in liquid and gaseous phases, and reaction takes place above liquid slag in gaseous phase. Slag layer ensures titanium separation from unreacted magnesium and magnesium chloride, and other reaction waste products. Titanium droplets filtrate through the slag and is separated from the other fractions. In this paper we test the feasibility of this idea by studying the electroslag remelting of a titanium electrode in a specially prepared laboratory reactor. Chemical analysis is done to measure the composition of reaction products.

Экспериментальное изучение вращения шлаковой и металлической ванн при электрошлаковом процессе в токоподводящем кристаллизаторе

Экспериментальное изучение вращения шлаковой и металлической ванн при электрошлаковом процессе в токоподводящем кристаллизаторе

Experimental study of slag and metal pool rotation during the electroslag process in current-supplying mould

Experimental study of slag and metal pool rotation during the electroslag process in current-supplying mould

Electroslag refining with liquid metal for composite rotor manufacturing

Purpose: To develop novel ESR based process for composite ingot with shallow transition zone between layers in order to produce efficient heavy-weight rotors for steam turbines. Design/methodology/approach: The nowadays heavy-weight rotors for steam turbines for power plants are monoblock or two or more layer in length composite part facilitating operation in different zones withstanding various loads and working medium. However, the joining of various steel in composite rotors by welding has low productivity. The ESR now is recognised as the best available technology for the big-diameter and mass forgings for power generating machines, including rotor ones. The ESR affords the most favourable conditions of solidification resulting in homogenous low-segregation ingot with smooth surface and high-quality structure. The step ahead is the ESR for composite. Findings: The two-layer model ingot had produced from steel grades 12Cr13 and 35NiCrMoV12-5 were manufactured using the electroslag process with the liquid metal (ESR LM) in the CSM of 180 mm in diameter with ingot withdrawing. The transition zone in two-layer ingot had have the shallow shape and low depth with the even macrostructure without defects of the same type as both joined steels. The metal of the transition zone fully satisfies standard requirements for properties of both steel grades in the heat treated and as-cast conditions. Research limitations/implications: The ESR LM can provide both the monobloc heavy ingots with uniform structure and composites with low-stress connection between metal layers for heavyweight rotors and other critical products manufacturing.

Electroslag Treatment of Liquid Cast Iron

The processes that occur in the liquid metal–slag system during electroslag treatment of cast iron are studied from an electrochemical standpoint. The role of electrolysis in the electroslag process is shown, and a method for producing high-strength cast iron with globular graphite using electrolysis of a slag containing magnesium oxides and fluorides is proposed and tested.