Numerical simulation of the protective gas electro slag. Vacuum arc remelting is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. Computational modeling, vacuum arc remelting, var, titanium alloys, macrosegregation, inclusion. British industrial furnace constructors association bifca. In the vacuum arc remelting var furnace, the dc electric current is passed through the electrode. Vacuum arc melting of magnetic and not magnetic metals, ceramics and minerals. Vacuum arc remelting is the continuous remelting of a consumable electrode by means of an electric dc arc between the electrode and the base of a copper mold. Multiple input electrode gap control during vacuum arc remelting. Vacuum arc remelting and electroslag remelting processes are used to produce large five tonne ingots of nickelbased superalloys, titanium alloys, and other highvalueadded alloys.
At the high melting currents 30 to 40 ka typically used for var of segregation insensitive ti and zr alloys, process voltage is used as an indicator of electrode gap, whereas dripshort. A numerical model of the vacuum arc remelting var process was used to study multistage var processes. Rendering of electroslag remelting apparatus and crosssections electroslag remelting esr, also known as electroflux remelting, is a process of remelting and refining steel and other alloys for missioncritical applications in aircraft, thermal power stations, nuclear power plants, military technology, etc. This is accomplished through the application of a high current that melts the material through the emergence of electrical arcs that induce joule heating. Var vacuum arc remelting 11 vacuum system intecos vacuum system is designed for utmost flexibility and minimized pump down times, which can be achieved by one threestage mechanical pumping unit and, for fine vacuum, one oil booster ejection unit. Certificates the following documents may be viewed or downloaded as pdf files.
Vacuum arc remelting var is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. The vacuum arc remelting var process is widely used to improve the cleanliness and refine the structure of standard air melted or. The size of the electrode gap has a direct influence on ingot solidification structure. Vacuum arc remelting furnaces var furnaces for melting material that have already been melted and cast into electrodes that are near their full packing density. We were the first to apply load cell weighing of electrodes to improve process control. Accurate control of the electrode gap in a vacuum arc remelting var furnace has been a goal of melters for many years. In vacuum arc melting the chamber is evacuated and then back filled with argon gas. Modeling of vacuume arc remelting of alloy 718 ingots. The var process is carried out with the aim of melting a large consumable electrode in such a way that the resulting ingot has improved homogeneity. Pericleous vacuum arc remelting var aims at production of high quality, segregationfree alloys.
The calco soft 2d software is fem based and solves the heat flow equation in 2dimensional systems. Analyses of the flow and heat transfer phenomena in the var process are presented by bertram 4et al. A vacuum arc re melting furnace to produce metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. In order to meet strict cleanliness specifications, ecfg has the capability to provide vacuum arc remelt var material. Vacuum arc remelting casting handbooks asm international. Computational modeling of the vacuum arc remelting var process used for the production of ingots of titanium alloys kanchan m.
The superheat is estimated by multiplying the fraction of arc energy that goes into the melt by the power of the arc per electrode crosssection. Var is the continuous remelting of a consumable electrode by means of an arc under vacuum. During var vacuum furnace, an electric arc is struck at the tip of an air melted ingot known as an electrode, melting the material within the vacuum container. Vacuum arc remelting furnaces var consarc engineering. For highest quality demands, deutsche edelstahl werke use the electroslag remelting esr as well as the vacuum arc remelting procedure.
Vacuum arc re meltingvar is a melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. The var process is carried out with the aim of melting a large consumable electrode in such a. The var process has revolutionized the specialty traditional metallurgical techniques industry, and has made possible incredibly controlled materials used in the biomedical. Main modeling challenges for vacuum arc remelting var are briefly.
Pdf modeling of the vacuum arc remelting process for estimation. The studies of low and high power 3xvar confirmed the results of the single stage process studies for ti1023. Improvement in mechanical properties of c300 maraging steel. Electroslag remelting esr and protective gas electroslag remelting pesr. A parametric study of the vacuum arc remelting var process. Fig ure 5 shows the basic design of the vader process with a static crucible. The energy required for melting is created by applying an electric voltage, which generates an arc between the electrode tip and the metal sump below, produced by the molten ingot. Arc distribution during the vacuum arc remelting of ti6al4v c.
Var steels and specialalloys, as well as titanium and zirconium and their alloys, are used in a large number of high integrity applications, where cleanliness, homogeneity and improved fatigue properties in the final product are essential. Pdf vacuum arc melting processes for biomedical niti shape. A multiscale 3d model of the vacuum arc remelting process. Vacuum arc remelting furnaces background pioneers in var technology consarc is well known to producers of speciality steel, superalloys, and reactive metals. Computational modeling of the vacuum arc remelting var. Each of the pumping units is switchable individually as well as in series. Rigel woodside for the degree of doctor of philosophy in mechanical engineering presented on june 4, 2010 title. Nowadays vacuum arc remelting var process is used for production of highquality alloys with uniform microstructure and high mechanical properties such as strength and toughness 3.
During the remelting process, a consumable electrode is melted under a vacuum. Schematic diagram of the vacuum arc remelting var process courtesy ati allvac, 2003. Pdf on the modeling of vacuum arc remelting process in. Throughout the critical stage of melting, exact composition is. The quality of the produced ingots depends on the operating conditions which could be monitored and analyzed using numerical modelling. A comprehensive simulation tool for the vacuum arc remelting var process. The change in primary dendrites growth direction, determined by the pool shape, leads to nonisotropic material properties in terms of plastic flow. This process is said 3 to produce directional structure due to its metallic water cooled mould. King, and chris nordlund currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting var is not a known or monitored process parameter. Pdf a parametric study of the vacuum arc remelting var.
Effects of arc radius, side arcing, and gas cooling article pdf available in metallurgical and materials transactions b 514. Pdf this study primarily involved using a vacuum arc remelting var process to prepare a nitinol shapememory alloy with distinct ratios of alloy. Heating is via an electric arc struck between a tungsten electrode and metals placed in a depression crucible in the copper hearth. The transient behavior of the arc was characterized using the external magnetic field and surface current measurements, which were. This report addresses a mechanical property characterization of a split argonoxygen decarburized aod heat of 4340 steel which was further processed by vacuum arc remelting var and electroslag remelting esr into 12. Intense heat generated by the arc melts the tip of the electrode while a new ingot is progressively formed below in. We pioneered commercial ingot production using automated vacuum arc remelting var furnaces. An introduction to premium melting carpenter technology. Consarc utilizes fully computerized controls to optimize reproducibility and ease of operation. Exposure of molten metal droplets to vacuum reduces free gas content in the steel providing a cleaner product with little segregation. The var process for ingot production vacuum arc remelting is a consumable electrode alloys, superalloys, and steel. Within the var furnace the copper mold is contained by a water jacket.
Var is widely used to improve the cleanliness and refine the structure of standard airmelted or vacuum induction melted ingots, and then called consumable electrodes. Contractors health and safety assessment scheme chas. Var vacuum arc remelt matrial for cleanliness specifications. Thermal treatment nitration and oxidation of metals. Remelting occurs under vacuum at a pressure of only approx. Electrode gap is a very important parameter for the safe and successful control of vacuum arc remelting var, a process used extensively throughout the specialty metals industry for the production of nickel base alloys and aerospace titanium alloys. Based on these experiences involving direct electrical currents in metallurgical processes, the scope of calcosoft2d was extended to cover also the esr process, taking alternating currents. Optimal estimation of electrode gap during vacuum arc. Vacuum arc remelting furnaces var vacuum aluminum brazing furnaces vab electroslag remelting furnaces esr induction skull melting furnaces ism. Multiple input electrode gap control during vacuum arc. Optimal estimation of electrode gap during vacuum arc remelting. Vacuum arc remelting furnaces var inductotherm group india.
The arc used in the var furnace can break up inclusions. The change in primary dendrites growth direction, determined by the pool shape, leads to nonisotropic material properties in. Vacuum arc remelting var is a secondary melting process for exotic alloys. Metal droplets form on the bottom of the electrode in an analogous fashion to esr, thereby melting the electrode inside the. Implementation of a highfidelity axisymmetric model in a.
Electroslag remelting esr, also known as electroflux remelting, is a process of remelting and refining steel and other alloys for missioncritical applications in aircraft, thermal power stations, nuclear power plants, military technology, etc the electroslag remelting esr process is used to remelt and refine steels and various superalloys, resulting in highquality ingots. Var skull melter titanium casting titanium casting is increasingly selected as an economical manufacturing method for near net shaped components. At higher pressures and longer gap lengths, however, scattering interactions with the relatively cold ambient gas begin to remove significant amounts of energy from the arc plasma, interfering with the. By vacuum arc remelting, billets from ingot cast material or continuously cast blooms are melted under a vacuum atmosphere. Hhv has attained the level of expertise in design, developing vacuum technology based equipment, quality in par with the international standards. Vacuum arc remelting vacuum arc remelting var is another secondary refining process that enhances the quality of metal that had undergone primary air melting andor was melted, or remelted, in arc, vim or esr furnaces. The var feedstock is consumable electrodes produced by vim or conventional air melting. Metal droplets from the electrode drip into a watercooled copper crucible forming an ingot topped by a molten pool 1, as seen in figure 1. Arc distribution during the vacuum arc remelting of ti6al4v. Pdf vacuum arc remelting var is an industrial metallurgical process widely used.
As the melting electrode drips into the bottom of the vessel, the surface area of each falling drip is exposed to the environment of the vacuum, which removes any residual gases from the alloy. Vacuum arc remelting furnace, this is a consumable electrode remelting process performed inside a vacuum chamber. An abstract of the dissertation of doctor of philosophy in. Vacuum arc remelted var billets sandvik materials technology. Tool steels produced under protective atmosphere such as vacuum arc remelting var produce cleaner steels with better structural homogeneity compared to electro slag remelting. Vacuum arc remelting is a casting process where a consumable electrode is melted under vacuum at a carefully controlled rate using heat generated by an electric arc struck between the electrode and the ingot. We operate electric arc furnaces, argonoxygen refining vessels, vacuum induction melting furnaces, vacuum arc remelting furnaces, electroslag remelting furnaces and an air induction melting furnace. Currently, the temporal arc distribution across the ingot during the vacuum arc remelting var process is not a known or monitored parameter. Computational investigation on the effects of arc location in. Impurities and inclusions can nucleate cracks when subjected to stresses. Optimal estimation theory has been applied to the problem of estimating electrode gap and a filter has been developed based on a model of the gap. The intent is to produce a sound ingot with uniform cleanliness and chemical homogeneity.
Patankar1, alec mitchell2, osamu kanou3, nobuo fukada3, kenji suzuki3 1innovative research, inc. Applications include commercial goods golf clubs, industrial components pump bodies, medical parts implants and of course various components for the aircraft industry. Remelting variations under vacuum apart from the remelting of a consumable electrode in a watercooled copper crucible, there is a recent development of the vacuum arc remelting process, namely vacuum arc double electrode remelting vader. The study by hans4 also includes analysis of macrosegregation. Vacuum arc remelting var is a secondary process used for homogenization of highmeltingpoint and oxygensensitive materials such as superalloys and titanium alloys.
Evaluation of the electroslag remelting process in medical. As the melting electrode drips into the bottom of the vessel, the surface area of each falling drip is exposed to the environment of the vacuum, which. Arc remelting furnace a vacuum arc re melting furnace to produce metal ingots. At higher pressures and longer gap lengths, however, scattering interactions with the relatively cold ambient gas begin to remove significant amounts of energy from the arc plasma, interfering with the arc conduction mechanism. Electroslag remelting esr in this process, there is a slowly melting consumable electrode and a watercooled mold for solidification, as in vacuum arc remelting, but the melting is conducted under normal atmosphere and is accomplished by a thick, superheated layer of slag on top of the shallow metal pool. Segregation development in multiple melt vacuum arc remelting. The var process has revolutionized the specialty traditional metallurgical techniques industry, and has made possible incredibly controlled materials used in the biomedical, aviation, and aerospace fields. Other articles where vacuum arc remelting is discussed. Downloads vfe heat treatment industry equipment servicing. For efficient production, we also utilize continuous casting where feasible. The main process stages o a consumable var electrode is generated by vim, esr, eb or plasma methods, assembled from titanium sponge, scrap or bulk, or by a prior var melt o dc power is applied to strike an arc between the electrode and the. Compactvar reference manual, 2006, innovative research. On the modeling of vacuum arc remelting process in titanium alloys view the table of contents for this issue, or go to the journal homepage for more 2016 iop conf.
The main objective of vacuum arc remelting is to control solidification conditions in order to obtain a columnar dendritic structure throughout the whole ingot. Arc distribution and motion during the vacuum arc remelting process as detected with a magnetostatic approach. A threedimensional, transient, multiscale model of the var process is presented, allowing novel simulations of the influence of fluctuations in arc behavior on the flow and heat transfer in the molten pool and the effect this has on the microstructure and defects. Computational modeling, vacuum arc remelting, var, titanium alloys, macrosegregation, inclusion behavior 1 introduction the vacuum arc remelting process var is a type of consumable electrode remelting processes used for producing ingots of superalloys and titanium. Vacuum arc remelting var spang power electronics is a manufacturer of custom power equipment installed throughout the var industry for the refining of steels, superalloys, titanium, and zirconium.
Improvement in mechanical properties of c300 maraging. Computational investigation on the effects of arc location. Vacuum arc remelting is the continuous remelting of a consumable electrode by means of an electric dc arc between the electrode and the base of a. Figure 1 shows a schematic diagram of the var process that uses. The main purpose of this process is to increase the input ingots physical and chemical homogeneity. This kind of stainless steel is in the \ultra clean steel categories, which are manufactured with some special processes such as vim vacuum induction melting, var vacuum arc remelting, and esr electro slag re. The electric arc that is created is similar to a welding arc and produces the heat necessary for remelting of the electrode. Vacuum arc remelting var is a process in which an electrode is melted in vacuum by the heat from a dc arc. Numerical simulation of the protective gas electro slag remelting process and its industrial validation a. In a previous project, a model simulating the vacuum arc remelting var process had been successfully implemented into calcosoft2d 67. In this process, employed for casting steels that contain easily oxidized alloying elements, a consumable electrode made of forged steel or of compacted powder or sponge is continuously melted by an arc under vacuum.
1331 1434 675 767 89 343 1357 289 439 555 407 1278 1394 441 891 1377 1163 507 219 385 512 1027 1466 637 1141 1104 1061 1468 76 1084 1151