Vacuum Arc Remelting (VAR
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ALD Vacuum Technologies High Tech is our Business Vacuum Arc Remelting (VAR) Vacuum Arc Remelting Processes and Furnaces

Vacuum Arc Remelting (VAR) ALD is one of the leading suppliers of vacuum melting furnace technologies for engineered metals VAR is widely used to improve the cleanliness and refine the structure of standard airmelted or vacuum induction melted ingots (called consumable electrodes). VAR steels and superalloys as well as titanium and zirconium and its alloys are used in a great number of high-integrity applications where cleanliness, homogeneity, improved fatigue and fracture toughness of the final product are essential. OO Aerospace OO Power generation OO Chemical Industry OO Medical and...

VAR Advantages & ALD Features ALD has numerous references in the field offering the highest levels of system automatization Further advantages Features of VAR furnaces from ALD OO Removal of dissolved gases, such as hydrogen, nitrogen and CO OO Reduction of undesired trace elements with high vapor pressure OO Achievement of directional solidification of the ingot from bottom to top OO Elimination of macro-segregation and reduction of micro-segregation OO Improvement of oxide cleanliness OO Removal of Oxides by chemical and physical processes OO Removal of Nitrides by thermally dissociation...

Process Technology and Process Characteristics ALD´s process expertise guarantees high process reproducibility and material quality VAR is the continuous remelting of a consumable electrode by means of an arc under vacuum The main process stages OO 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 OO DC power is applied to strike an arc between the electrode and the baseplate of a copper mold contained in a water jacket OO The intense heat generated by the electric arc melts the tip of the...

Directional Solidification of the Vacuum Arc Remelting Process Precise control of the local solidification rate of the temperature gradient at the liquid/solid interface Achieving the optimum VAR ingot solidification structure requires precise control of the local solidification rate and the temperature gradient at the liquid/solid interface. High Temperature Gradient Melt Pool Profile at the solidification front must be maintained during the entire remelting process to achieve a directed dendritic primary structure. As pool depth increases with the remelting rate, the growth angle of the...

Understanding and Preventing Solidification Defects Metallurgists agree that in spite of directional solidification, defects such as “tree ring patterns”, “freckles” and “white spots” can occur in remelted ingots. These defects can lead to rejection of the ingot, particularly in the case of special alloys. Tree ring patterns White Spots OO Can be identified in a macro-etched transverse section as light-etching rings OO Usually represent a negative crystal segregation OO Seem to have little effect on material properties OO White spots are typical defects in VAR ingots. They are recognizable...

ALD VAR Furnaces Design Features Schematic of the VAR furnace 1 Electrode feed drive 2 Furnace chamber 3 Melting power supply 4 Busbars/cables 5 Electrode ram 6 Water jacket with crucible 7 Vacuum suction port 8 X-Y adjustment 9 Load cell system Design Features of all ALD VAR Furnaces OO Gantry design of furnace head super structure features simple platform installation with no flexure of the superstructure under load. Consistent centering of the electrode. OO Proven electro-mechanical dual electrode drive system for very precise control of small melt speeds during the remelting process and...

VAR Process Control ALD’s automatic melt control system (AMC) is unsurpassed in the world for its accuracy, reproducible metallurgical quality and ease of operation ALD provides precise control of all VAR remelting parameters for reproducible production of homogeneous ingots, which are free of macro-segregation and show controlled solidification structure and superior cleanliness Communication via field bus or specific interfaces ALD’s VAR control systems handle: OO Logic control functions OO Continuous weighing of the consumable electrode OO Closed loop control of process parameters (e.g....