text: VAR is used most frequently in high value applications. It is an additional processing step to improve the quality of metal.  Because it is time consuming and expensive, a majority of commercial alloys do not employ the process.  Nickel, titanium, and specialty steels are materials most often processed with this method.  The conventional path for production of titanium alloys includes single, double or even triple VAR processing.  Use of this technique over traditional methods presents several advantages:
  *The solidification rate of molten material can be tightly controlled.  This allows a high degree of control over the microstructure as well as the ability to minimize segregation
  *The gases dissolved in liquid metal during melting metals in open furnaces, such as nitrogen, oxygen and hydrogen are considered to be detrimental to the majority of steels and alloys. Under vacuum conditions these gases escape from liquid metal.
  *Elements with high vapor pressure such as carbon, sulfur, and magnesium (frequently contaminants) are lowered in concentration.
  *Centerline porosity and segregation are eliminated.
  *Certain metals and alloys, such as Ti, cannot be melted in open air furnaces