Vacuum Arc Remelting (VAR)

For VAR (Figure 3), raw material are used as consumable electrode in water-cool copper crucible, as consumable electrode. A small amount of alloy to be remelted is placed at the bottom of the crucible. Feed current between raw material and crucible, electrical arc is struck between the raw material and the crucible to melt material at the bottom [2]. The metal melts continuously and the top electrode is gradually moved downwards by a mechanical ram in such a way that the arc is maintained steadily between the electrodes. The crucible is cooled with water jackets and solidification of the material is closely controlled. The quality of the resulting alloy is dependent on the cooling rate, gap between the electrodes and current. This refining process need repeated several times to promote its homogeneity. Nickel, titanium and special steels are often processed using VAR. [4]

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Figure 3. sketch of VAR.

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Figure 4. A visual depiction of VAR process.

A more advanced process is the VIM/VAR association. Ni and Ti are first melted in the VIM furnace and then subjected to the VAR or multiple VAR process. Low carbon level of copper crucible and high accuracy of pressure and raw material control both meet the requests of making high purity nitinol [1].

From the report published by the European Commission including critical materials for Europe, and the ‘Final List of Critical Minerals’ which is significant for the security and economic of the US, we can find that titanium is a kind of critical material, but nickel is not. Titanium is widely used as metal alloy and paint.[5]

It is important for the security and economic of every county, and it plays a vital role in the manufacture of products. As a common element and complete industrial chain, the use of nickel is extensive both in commercial and military industrial manufacturing field. [6]

Nitinol

Nitinol

Processing Route

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