Titanium melting system improves melt properties. (New technology).European firm Titane et Alliages Rares Micro-Moules (Taramm) is providing a titanium production melting process that combines cold crucible crucible, vessel in which a substance is heated to a high temperature, as for fusing or calcining. The necessary properties of a crucible are that it maintain its mechanical strength and rigidity at high temperatures and that it not react in an undesirable way with melting and centrifugally assisted pouring for improved metallurgical integrity and dimensional tolerances. At the heart of the process is a furnace that accommodates the melting and pouring systems while using conventional vacuum pumping equipment. The firm's copper crucible is segmented , with each section water-cooled and insulated from each adjacent segment. This design causes the induced current In`duced´ cur´rent 1. (Elec.) A current due to variation in the magnetic field surrounding its conductor. to loop around each segment and creates the required magnetic field in the metallic charge. The metal is heated quickly, begins to melt and fills the base of the crucible, where a small volume solidifies and forms a local thin skull of metal. As melting nears completion, the electromagnetic force electromagnetic force One of the four known basic forces in the universe. Electromagnetism is responsible for interactions between charged particles that occur because of their charge, and for the emission and absorption of photons (electromagnetic radiation). concentrates in the center of the crucible, reducing metal-mold contact. The charge is then partially levitated, and the metal becomes superheated su·per·heat tr.v. su·per·heat·ed, su·per·heat·ing, su·per·heats 1. To heat excessively; overheat. 2. . This process can be controlled for charge weights up to 5 kg. This provides advantages in terms of filling thin sections in the mold and the overall length of flow compared with the vacuum arc remelting Vacuum Arc Remelting (VAR) is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. process. The constant and vigorous stirring of the titanium by the induced electromagnetic forces offers optimum chemical and thermal homogeneity Homogeneity The degree to which items are similar. in the melt. The crucible then is tilted and the titanium is poured into a ceramic mold rotating at high speed. To maintain the temperature of the melt, power is applied during pouring. The filling of the mold cavities is accelerated by the increasing pressure exerted toward the outer diameter of the mold by the spinning forces. This promotes filling of section cavities as thin as 0.5 mm. The metal charge weight is adjusted for each mold configuration to ensure filling of each casting and its feeder while leaving a significant portion of the downsprue devoid of metal. The process has been used to produce [Ti.sub.6][Al.sub.4]V, commercially pure titanium and titanium-aluminum eutectic alloy eu·tec·tic alloy n. An alloy that is generally brittle, easily melted, and subject to tarnish and corrosion, used primarily in dental solders. castings but nickel-base alloys such as IN 718 also are compatible with the process. |
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