Method for making hollow cylinders of vitreous silica by vacuum heating

Abstract

Abstract Hollow cylinders and tubes are made from vitreous silica by placing granular or powdered quartz or silica starting material on a granular bedding layer in a hollow form revolving about its axis and, as the rotation of the hollow form continues, melting by means of an electrical power source, and solidifying the starting material. An electrically heated hollow cylinder of carbonaceous material is disposed in the hollow form and the apertures thereof are hermetically closed with covers after the starting material has been put in. The sealed inner chamber thus formed is slowly evacuated with a vacuum to a pressure ranging from 10 to 0.0001 mm Hg. The starting material is slowly heated to the melting point while sustaining this pressure. After complete melting, the electric power source is shut off and the fused article is cooled while rotation continues. Thereafter, the vacuum pump is shut off and the inner chamber is aired before removing the cover. Lastly, the vitreous silica hollow cylinder which is still at temperatures between room temperature and 1,400*C., is removed from the hollow form. Apparatus for making hollow cylinders from vitreous silica via the above-described process includes horizontally disposed, rotatable hollow form means adapted to be hermetically sealed with a cover means having a vacuum connection connected to vacuum means. Crucible means are positioned within the form means and graphite vacuum baffle means extends into the hollow form means and the crucible means. A filling of refractory thermal insulation material is between the crucible means and the hollow form means.

Inventors

• 👤 K Rau

Bibliographic Details