acuum induction melting (VIM) is on

acuum induction melting (VIM) is one of the
most commonly used processes in secondary metallurgy
applied for refining treatment in
the liquid state and adjustment of chemical composition
and temperature. To achieve
the increasing quality demands on the
resulting material and at the same time
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save raw materials such as alloying
elements due to higher yield; and
save energy,
Vacuum induction melting makes possible
effective degassing of the melt and extra- ordinarily
precise adjustment of alloy
composition, since the temperature, vacuum,
gas atmosphere, pressure and material
transport (e.g., through stirring of the bath)
can be adjusted independently of one
another. Besides the exact concentration
of alloying elements, the content of trace
elements is also important for many alloys. Sampling
the application of vacuum in the induction
melting process is a must for many specialized
materials. For example, vacuum induction
melting is indispensable in the manufacture
of special alloys, which must be melted
under vacuum or in an inert gas atmosphere because of
their reactivity with atmospheric
oxygen. The process is suitable for the
production of high-purity metals within an oxygen-free
atmosphere. This limits the
formation of non-metallic oxide inclusions.
Metallurgical Advantages
are:
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Melting under oxygen-free atmosphere,
this limits formation of non-metallic
oxide inclusions and prevents
oxydation of reactive elements;
Achievement of very close
compositional tolerances and gas
contents;