Patent ID: 8416833
Filing Date: 2013-04-09
Classification: C03B,H05B

Abstract:
1. An apparatus for manufacturing a fused silica crucible by molding raw powder into a mold for crucible forming and heating and melting the compact thereof by arc discharge, comprising: a mold for charging and molding raw powder; and an arc discharge apparatus for heating and melting a non-conductive object by arc discharge using a plurality of carbon electrodes in an output range of 300 to 12,000 kVA, the carbon electrodes which are arranged such that a ratio of the distance between a contact position at which the carbon electrodes come in contact with each other and a front end to the diameter of the carbon electrode is in the range of 0 to 0.9, wherein the difference between the densities of the carbon electrodes is less than or equal to 0.2 g/cm wherein a power density of the carbon electrodes is set to be in the range of 800 to 1,200 kVA/cm wherein a ratio of the diameter of the carbon electrodes to a length consumed per unit during arc discharge is in the range of 0.02 to 0.6, wherein the carbon electrodes have a contact portion including the contact position at the front end, and wherein the shape of the contact portion is a cone shape of which the diameter decreases toward the front end, a truncated cone shape, or a curve shape in which curvature breakpoints do not exist in a cross-sectional outline along the axial line of the carbon electrode.