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. Heating is via an electric arc struck between a tungsten electrode and metals placed in a depression crucible in the copper hearth. 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. 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. Consarc utilizes fully computerized controls to optimize reproducibility and ease of operation. In the vacuum arc remelting var furnace, the dc electric current is passed through the electrode.
Multiple input electrode gap control during vacuum arc. Within the var furnace the copper mold is contained by a water jacket. Currently, the temporal arc distribution across the ingot during the vacuum arc remelting var process is not a known or monitored parameter. The quality of the produced ingots depends on the operating conditions which could be monitored and analyzed using numerical modelling. 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. A numerical model of the vacuum arc remelting var process was used to study multistage var processes. The change in primary dendrites growth direction, determined by the pool shape, leads to nonisotropic material properties in. A multiscale 3d model of the vacuum arc remelting process. Numerical simulation of the protective gas electro slag. Vacuum arc remelting furnace, this is a consumable electrode remelting process performed inside a vacuum chamber.
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. This process is said 3 to produce directional structure due to its metallic water cooled mould. Pdf modeling of the vacuum arc remelting process for estimation. Computational modeling of the vacuum arc remelting var. Vacuum arc remelting and electroslag remelting processes are used to produce large five tonne ingots of nickelbased superalloys, titanium alloys, and other highvalueadded alloys. Thermal treatment nitration and oxidation of metals. The change in primary dendrites growth direction, determined by the pool shape, leads to nonisotropic material properties in terms of plastic flow. Pdf on the modeling of vacuum arc remelting process in. Vacuum arc melting of magnetic and not magnetic metals, ceramics and minerals. The var process for ingot production vacuum arc remelting is a consumable electrode alloys, superalloys, and steel. Exposure of molten metal droplets to vacuum reduces free gas content in the steel providing a cleaner product with little segregation. 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.
Vacuum arc remelting var is a secondary process used for homogenization of highmeltingpoint and oxygensensitive materials such as superalloys and titanium alloys. Optimal estimation of electrode gap during vacuum arc. Fig ure 5 shows the basic design of the vader process with a static crucible. A parametric study of the vacuum arc remelting var process. 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. Vacuum arc remelting is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. 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. Improvement in mechanical properties of c300 maraging steel. 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. Hhv has attained the level of expertise in design, developing vacuum technology based equipment, quality in par with the international standards. The var feedstock is consumable electrodes produced by vim or conventional air melting.
Arc distribution and motion during the vacuum arc remelting process as detected with a magnetostatic approach. 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. A comprehensive simulation tool for the vacuum arc remelting var process. The studies of low and high power 3xvar confirmed the results of the single stage process studies for ti1023. Arc distribution during the vacuum arc remelting of ti6al4v. Main modeling challenges for vacuum arc remelting var are briefly. Rigel woodside for the degree of doctor of philosophy in mechanical engineering presented on june 4, 2010 title.
Pdf vacuum arc remelting var is an industrial metallurgical process widely used. Arc distribution during the vacuum arc remelting of ti6al4v c. Each of the pumping units is switchable individually as well as in series. In vacuum arc melting the chamber is evacuated and then back filled with argon gas. Vacuum arc remelting furnaces var vacuum aluminum brazing furnaces vab electroslag remelting furnaces esr induction skull melting furnaces ism. This is accomplished through the application of a high current that melts the material through the emergence of electrical arcs that induce joule heating. Contractors health and safety assessment scheme chas. An introduction to premium melting carpenter technology. Accurate control of the electrode gap in a vacuum arc remelting var furnace has been a goal of melters for many years. 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 remelting.
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. 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. Intense heat generated by the arc melts the tip of the electrode while a new ingot is progressively formed below in. Applications include commercial goods golf clubs, industrial components pump bodies, medical parts implants and of course various components for the aircraft industry. Numerical simulation of the protective gas electro slag remelting process and its industrial validation a. In order to meet strict cleanliness specifications, ecfg has the capability to provide vacuum arc remelt var material. Schematic diagram of the vacuum arc remelting var process courtesy ati allvac, 2003. Var vacuum arc remelt matrial for cleanliness specifications. Vacuum arc remelting var is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. Implementation of a highfidelity axisymmetric model in a. 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. Arc remelting furnace a vacuum arc re melting furnace to produce metal ingots. 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. Computational modeling, vacuum arc remelting, var, titanium alloys, macrosegregation, inclusion.
Impurities and inclusions can nucleate cracks when subjected to stresses. Vacuum arc remelting var is a secondary melting process for exotic alloys. Effects of arc radius, side arcing, and gas cooling article pdf available in metallurgical and materials transactions b 514. The var process is carried out with the aim of melting a large consumable electrode in such a. 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. Vacuum arc remelting furnaces var consarc engineering.
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. An abstract of the dissertation of doctor of philosophy in. 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. Vacuum arc remelting casting handbooks asm international. Computational investigation on the effects of arc location in. Electroslag remelting esr and protective gas electroslag remelting pesr. Pdf this study primarily involved using a vacuum arc remelting var process to prepare a nitinol shapememory alloy with distinct ratios of alloy. Vacuum arc remelting furnaces var inductotherm group india.
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. Modeling of vacuume arc remelting of alloy 718 ingots. 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. We were the first to apply load cell weighing of electrodes to improve process control. Vacuum arc remelting var is a process in which an electrode is melted in vacuum by the heat from a dc arc. Throughout the critical stage of melting, exact composition is.
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. The size of the electrode gap has a direct influence on ingot solidification structure. During the remelting process, a consumable electrode is melted under a vacuum. 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. Improvement in mechanical properties of c300 maraging.
Tool steels produced under protective atmosphere such as vacuum arc remelting var produce cleaner steels with better structural homogeneity compared to electro slag remelting. The intent is to produce a sound ingot with uniform cleanliness and chemical homogeneity. Vacuum arc re meltingvar is a melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. Var is the continuous remelting of a consumable electrode by means of an arc under vacuum. The main objective of vacuum arc remelting is to control solidification conditions in order to obtain a columnar dendritic structure throughout the whole ingot. The transient behavior of the arc was characterized using the external magnetic field and surface current measurements, which were. Pericleous vacuum arc remelting var aims at production of high quality, segregationfree alloys. 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.
For efficient production, we also utilize continuous casting where feasible. 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. Other articles where vacuum arc remelting is discussed. Analyses of the flow and heat transfer phenomena in the var process are presented by bertram 4et al.
Computational investigation on the effects of arc location. Multiple input electrode gap control during vacuum arc remelting. The arc used in the var furnace can break up inclusions. The vacuum arc remelting var process is widely used to improve the cleanliness and refine the structure of standard air melted or. 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. By vacuum arc remelting, billets from ingot cast material or continuously cast blooms are melted under a vacuum atmosphere. Pdf vacuum arc melting processes for biomedical niti shape.
Pdf a parametric study of the vacuum arc remelting var. 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. 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. Vacuum arc remelting furnaces background pioneers in var technology consarc is well known to producers of speciality steel, superalloys, and reactive metals. Downloads vfe heat treatment industry equipment servicing. Vacuum arc remelted var billets sandvik materials technology. Remelting occurs under vacuum at a pressure of only approx. 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. Computational modeling of the vacuum arc remelting var process used for the production of ingots of titanium alloys kanchan m. We pioneered commercial ingot production using automated vacuum arc remelting var furnaces. The main purpose of this process is to increase the input ingots physical and chemical homogeneity. 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.
The electric arc that is created is similar to a welding arc and produces the heat necessary for remelting of the electrode. 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. 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. British industrial furnace constructors association bifca. Segregation development in multiple melt vacuum arc remelting. 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. For highest quality demands, deutsche edelstahl werke use the electroslag remelting esr as well as the vacuum arc remelting procedure. Certificates the following documents may be viewed or downloaded as pdf files.
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. A vacuum arc re melting furnace to produce metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. 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. Metal droplets form on the bottom of the electrode in an analogous fashion to esr, thereby melting the electrode inside the. Evaluation of the electroslag remelting process in medical. 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.
Var skull melter titanium casting titanium casting is increasingly selected as an economical manufacturing method for near net shaped components. The var process has revolutionized the specialty traditional metallurgical techniques industry, and has made possible incredibly controlled materials used in the biomedical. Compactvar reference manual, 2006, innovative research. 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. Patankar1, alec mitchell2, osamu kanou3, nobuo fukada3, kenji suzuki3 1innovative research, inc.