Vacuum induction melting, commonly abbreviated VIM, melts and refines metal by generating electric current directly in the metal itself through electromagnetic induction from a surrounding coil, with the entire furnace enclosed in a vacuum chamber so that reactive alloying elements do not oxidize and dissolved gases can be actively pulled out of the melt. The technique matured into industrial use in the 1950s as demand grew for nickel and cobalt-based superalloys and other reactive alloys whose performance depends on a level of purity and composition control that melting in open air could not reliably achieve. VIM is commonly used today as the first melting step for critical aerospace and medical alloys, frequently followed by a second refining stage such as vacuum arc remelting or electroslag remelting to reach the highest attainable levels of internal cleanliness.
Facts
Patent or First-Use Date SignificanceDeveloped to refine special metals such as cobalt and nickel, then widely adopted as those metals and alloys became more common. 1 FAQs
Why is steel melted in a vacuum instead of in open air?
Because a vacuum removes carbon, oxygen and hydrogen from the liquid steel.
Britannica describes vacuum induction melting, or VIM, as a method in which liquid steel is placed in a vacuum. In the vacuum, carbon, oxygen and hydrogen are removed from the steel, and their removal generates a boil in the crucible.
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Source Vacuum induction melting, Wikipedia
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1. Vacuum induction melting, Wikipedia
History, patent paragraph
Heraeus Vacuumschmelze and Dr. Wilhelm Rohn applied for a patent on vacuum melting on 12 January 1918 and were granted a German patent DE 345161.
History, patent application date
Heraeus Vacuumschmelze and Dr. Wilhelm Rohn applied for a patent on vacuum melting on 12 January 1918 and were granted a German patent DE 345161.
History, adoption paragraph
The process was initially developed to refine certain special metals such as cobalt and nickel. As these metals and alloys became more common, the vacuum induction melting (VIM) process became more widely adopted.
Lead section
The process was invented in Hanau, Germany in 1917.
In Field: Metallurgical Engineering, Categories
Metallurgical processes
In Group: Iron and Steel Making Processes, Article body
Edwin Fitch Northrup built the first prototype of a vacuum induction furnace in the United States of America in 1920.
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