Vacuum Induction Melting

 

Vacuum Induction Melting

 Vacuum induction melting (VIM) utilizes electric currents to melt metal within a vacuum. The first prototype was developed in 1920.One of the only ways to induce a current within a conductor is through electromagnetic induction. Electromagnetic induction induces eddy currents within conductors by changing the magnetic field. Eddy currents create heating effects to melt the metal. Vacuum induction melting has been used in both the aerospace and nuclear industries.
History
E.F. Northrup built the first prototype of a vacuum induction furnace in 1920 in the United States of America. In 1923, German scientist Wilhelm Rohn continued to advance the VIM technology along with founding the Heraeus melting facility. Medium frequency furnaces were seen soon afterwards in England and Sweden in 1927.The process was initially developed to refine certain special metals such as cobalt and nickel. As these metals and alloys became more common, the process of VIM became more widely used. VIM now helps to melt a variety of metals for aircraft and nuclear applications.
Procedure
Vacuum induction melting uses currents within a vacuum to melt metal. VIM involves placing a core-less induction furnace into a vacuum chamber.The heat used to start the melting process comes from an induced current called an eddy current. The melting and casting operations are then carried out at low pressures to control the entire alloy chemistry process.
Uses
VIM was usually used for refining high purity metal and alloys. VIM is now becoming more popular due to the variety of uses now available. The commercial production of nickel titanium alloys utilizes VIM to its full extent. Other examples of using VIM include melting steels for nuclear applications, cobalt alloy for medical applications, and both high purity copper alloy and clean magnetic alloy for high permeability.The process of VIM can even begin electro-slag remelting, which can remelt electrodes.
Nickel titanium
VIM is the most widely used process for the production of nickel titanium alloys. When producing nickel titanium, the process of VIM using a hot graphite crucible sometimes causes carbon contamination which causes some of the titanium ions to form titanium carbide (TiC). These TiC particles change the transformation temperature along with the strength of the alloy. This is one drawback with the process of vacuum induction melting in graphite.

The working principle of vacuum furnace

         The working principle of vacuum furnace

  Vacuum boiler is in a closed furnace internal form a negative pressure of vacuum, filling heat medium water in the body. By burning heating heat medium water or any other way, again by heat medium water evaporation, condensation and heat exchanger, again by heat exchanger to heat to heat water.
Vacuum boiler heat conversion signal:
Oil, natural gas, gas, electricity - > combustion heat (electric conversion) - > heat medium water - > after boiling steam condensation heat transfer of -- -- -- -- > > heat exchanger heat transfer > water
 Vacuum boiler working principle: using the characteristics of low water under the condition of low boiling point, rapid heating sealing furnace heat medium filled in water, high temperature steam, the heat medium water boiling evaporating out water vapor condenses on the heat exchange tube heat exchange tube in cold water, hot water supply.
Standard sea level atmospheric pressure: 1.013 x 105 pa = 101.3 KPa, the water's boiling point is 100 ℃; The higher the altitude, the lower atmospheric pressure, the boiling point is reduced:
The Tibetan plateau: the average altitude of 4000 m, atmospheric pressure of 62 kpa, at this time the boiling point of water is 87 ℃;
Mount Everest: up to 8848 m, 33 kpa atmospheric pressure, the boiling point is 71 ℃;
 Vacuum boiler by pumping air into vacuum state, almost no air to form a low pressure environment, and then use water (less than atmospheric pressure) under low pressure low temperature steam boiling, soda condensation heat transfer way will work the principle of heat output.
 Vacuum heat medium boiler water is after deoxidization, descaling and other special processing of high pure water, a filling to complete before they go out, when used within the unit closed cycle (vaporization and condensation and evaporation), does not increase, not decrease, in unit service life does not need to supplement or replace.
 Therefore, the vacuum inside the boiler furnace will never scale, corrosion, normal service life can reach more than 20 years, far more than ordinary hot water boiler the service life of 10 years or so.