Applications

Dental Technology

SIGRADUR® glassy carbon melting crucibles can be applied to dental technology for melting noble metal and titanium alloys. SIGRADUR® melting crucibles are notable for the following properties:

  • High thermal conductivity

  • Much longer service time than graphite crucibles

  • No adhesion of noble metal melts

  • Resistance to thermal shock

  • Suitability for all noble metal and titanium alloys

  • Use in induction-heated casting centrifuges

  • Generates a protective atmosphere over the metal melt

  • No melting salt required

SIGRADUR® glassy carbon crucibles eliminate the disadvantages of ceramic crucibles such as low thermal conductivity, adhesion of noble metal melts, and the need for melting salt. With SIGRADUR® melting crucibles, heating and melting times are reduced. The electric heating coil of the melting unit can be operated at lower temperatures than those of traditional ceramic vessels. The time needed for each casting is therefore reduced, and the life of the crucibles are extended. In addition, the absence of wetting eliminates issues such as material losses. SIGRADUR® glassy carbon crucibles have a much longer life than graphite crucibles. High purity, low specific surface, and an isotropic structure cause low and consistent oxidation, generating a protective atmosphere over the metal melt. This low oxidation rate prevents the formation of an oxide layer on the molten metal. The melting powder or pellets usually required with ceramic crucibles are not necessary, as the melt runs out freely without wetting the crucible wall.

The casting obtained has a uniform and clean appearance. The metal-repellent properties of the crucible remain unchanged throughout the product life. With their extremely good resistance to thermal shock, SIGRADUR® crucibles do not crack, even if placed on cold surfaces when red-hot.

SIGRADUR® crucibles are also suitable for use in induction-heated casting centrifuges. Since glassy carbon crucibles, unlike ceramic crucibles, couple in the inductive field and reach the operating temperature within a short timeframe, the metal will melt quickly and evenly.

Extensive tests have shown that SIGRADUR® crucibles are well-suited for melting high-palladium alloys. The finished castings do not have cavities and do not fade or flake after ceramic veneering.

SIGRADUR® is universally suitable for melting all palladium-based alloys and alloys with a reduced noble metal content. SIGRADUR® crucibles have also been employed for melting palladium-containing fused ceramic alloys with reduced noble metal content at temperatures around 1400°C.

SIGRADUR® crucibles should not be used for melting chromium-cobalt-molybdenum (steel) alloys.