Vacuum-induction-melting

Fig. 2. Schematic arrangement of a furnace in a vacuum chamber equipped with charging and mold locks for vacuum induction melting (1) (a) front cross...

The magnesium-reduced beryllium pebbles generally assay 96% beryllium and are always associated with residual magnesium and slag. These pebbles are purified to about 99.5% by vacuum induction melting in beryllia crucibles at temperatures of about 1400 °C. The ingots are machined and machined scarf is milled to produce beryllium powder. The ground metal powder is pressed and sintered under vacuum. The product is called vacuum hot-pressed beryllium, and this is machined for component manufacture. 

Chemical compositions plus processing and heat treatment schedules relative to Inconel 718 and Udimet 718 are presented in Tables I and II. Hardness and ASTM grain size (average numbers) are included in Table II. Both the Inconel 718 and Udimet 718 superalloys were obtained as large-diameter (29 cm and 26 cm, respectively) hot-finished forging billets, vacuum-induction-melted and vacuum-arc-remelted (VIM-VAR). The two alloys have comparable chemical compositions, but the Inconel 718 has a significantly higher silicon content. 

Process code HIP, hot isostatically pressed at 1200 C, 69 MPa for 2 hr. VIM, vacuum induction melted. VAR, vacuum arc remelted. EFR, electroflux remelted. 

Some superalloys, particularly Ni-Fe and Co based alloys, are directly melted in electric furnaces by classical methods usually applicable to stainless steels. However for Ni and special Ni-Fe superalloys, vacuum induction melting is required in order to reduce the content of interstitial gases (O, H, N) to a very low level. This enables foundries to achieve high and controlled contents of oxidisable elements such as Ti or Al. 

Nickel-titanium solid SMAs are manufactured by a double-vacuum melting process to ensure the quality, purity, and properties of the final material. After the formulation of raw materials, the alloy is vacuum-induction melted at 1400°C. After the initial melting, the alloy transition temperature must be controlled due to the sensitivity of the transition temperature to small changes in the alloy chemistry. This is followed by vacuum-arc remelting to... 

By argon-oxygen decarburization (ADD) the carbon content of commercial heats of 304L can now be reduced consistently to 0.01 %. AOD and vacuum induction melting are used to produce the new high-purity Fe-Cr-Mo ferritic stainless steels in Table 2. 

Vacuum induction melted alloy hot worked and annealed for 1 h at 950 C and air cooled. Standard Charpy V-notch impact specimens were machined. The influence of temperature on fracture toughness of 44Ti-49Ni-5Cu-2Fe (wt%). Note that the minimum in the fracture energy occurs just below M, as determined from the corresponding 0.2% yield strength and ultimate tensiie strength measurements. 

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