Vacuum Arc Remelting (VAR)  furnace

Vacuum induction melting furnace

vacuum arc furnace/vacuum melting furnace

VAR is widely used to improve the cleanliness and refine the structure of standard air-melted or vacuum induction melted ingots, then 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. Aerospace, power generation, defense, medical and nuclear industries rely on the properties and performance of these advanced remelted materials.

Process Technology and Process Characteristics
VAR is the continuous remelting of a consumable electrode by means of an arc under vacuum. DC power is applied to strike an arc between the electrode and the baseplate of a copper mold contained in a water jacket. The intense heat generated by the electric arc melts the tip of the electrode and a new ingot is progressively formed in the water-cooled mold. A high vacuum is being maintained throughout the remelting process.
The basic design of the VAR furnace has been improved continuously over the years particularly in computer control and regulation with the objective of achieving a fully- automatic remelting process. This in turn has resulted in improved reproducibility of the metallurgical properties of the products.

Metallurgy of the Vacuum Arc Remelting Process
The VAR ingot’s solidification structure of a given material is a function of the local solidification rate and the temperature gradient at the liquid/solid interface. To achieve a directed dendritic primary structure, a relatively high temperature gradient at the solidification front must be maintained during the entire remelting process. The growth direction of the cellular dendrites conforms to the direction of the temperature gradient, i.e., the direction of the heat flow at the moment of solidification at the solidification front. The direction of the heat flow is always perpendicular to the solidification front or, in case of a curved interface, perpendicular to the respective tangent. The growth direction of the dendrites is thus a function of the metal pool profile during solidification. As pool depth increases with the remelting rate, the growth angle of the dendrites, with respect to the ingot axis, also increases. In extreme cases, the growth of the directed dendrites can come to a stop. The ingot core then solidifies non-directionally, e.g., in equiaxed grains, leading to segregation and micro-shrinkage. Even in the case of directional solidification, micro-segregation increases with dendrite arm spacing.
 

Vacuum Arc Remelting (VAR)  furnace

Vacuum induction melting furnace

vacuum arc furnace/vacuum melting furnace

OEM products are acceptable.   

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