Electron-Beam Melting

melting in an electron-beam furnace at a high temperature and in high vacuum. Such conditions make possible many refining reactions that are unattainable in, for example, vacuum arc melting and induction melting in crucibles made from refractory oxides. Electron-beam melting is used for the production of especially pure refractory metals and alloys, as well as large steel and alloy castings for critical parts.

The major advantages of electron-beam melting are the following: (1) control within a wide range of the rate of melting, which provides a favorable macrostructure for the subsequent working of the casting, (2) the possibility of extreme superheating of the metal, which, in conjunction with a high vacuum, makes it possible to eliminate harmful impurities, such as nonferrous metals, (3) good degassing of the metal in a vacuum, (4) the absence of contact of the molten metal with a contaminating furnace lining, and (5) the possibility of remelting virtually any charge and of restarting the melting process after an accidental interruption without degrading the quality of the casting. In the production of large castings (up to several tens of tons), an important advantage of the process is the possibility of remelting relatively small billets introduced at intervals into the melting zone. Here, the molten metal enters a crystallizer, either directly from remelted stock or from an intermediate reservoir, and undergoes additional refining.

Electron-beam melting reduces the content of gaseous impurities and nonmetallic inclusions by a factor of 2–4 and increases the density and isotropy of the metal. Critical parts, such as rotors for powerful steam turbines, manufactured from metal melted in an electron-beam furnace have resistance to brittle failure twice as high as parts made from steel melted in an ordinary arc furnace and thus exhibit greater reliability.