Method and apparatus for manufacturing vitreous silica crucible
A method of manufacturing a vitreous silica crucible by a rotary mold method, which includes performing arc melting in a state in which electrodes are provided so as to be shifted from a mold central line, wherein, by this eccentric arc, the glass temperature difference during melting of a straight body portion, a curved portion and a bottom of the crucible is controlled to 300° C. or below and the thickness of a transparent layer of the straight body portion and the bottom is controlled to 70 to 120% of the thickness of a transparent layer of the curved portion.
1. A method of manufacturing a vitreous silica crucible by arc melting silica powder deposited on an inner surface of a rotary mold, wherein a plurality of electrodes are axially-symmetrically set with respect to an electrode position central line which is a vertical line equal to a central line which is a mold rotation center, wherein the arc melting is performed so as to switch electrodes powered during the arc melting with respect to the plurality of electrodes so that the direction of the arc flame generated during the arc melting is displaced from a mold rotating central line.
2. The method according to claim 1 , wherein the glass temperature difference during melting of a straight body portion, a curved portion and a bottom of the vitreous silica crucible is controlled to 300° C. or less by performing the arc melting in a state in which the electrodes are provided so as to be displaced from the mold central line.
3. The method according to claim 1 , wherein the thickness of a transparent layer of a straight body portion and a bottom of the vitreous silica crucible is controlled to 70 to 120% of the thickness of a transparent layer of a curved portion by performing the arc melting in a state in which the electrodes are provided so as to be displaced from the mold central line.