Apparatus and method of manufacturing silicon seed rod
A manufacturing apparatus of silicon seed rod in which two silicon seed rods are joined into one long silicon seed rod by welding, having: an upper seed rod holding part holding an upper silicon seed rod vertically; an elevating device holding a lower silicon seed rod which faces a lower end of the upper silicon seed rod in a state in which the lower silicon seed rod is movable vertically; an induction-heating coil being arranged around the lower end of the upper silicon seed rod; a preheating ring being disposed below the induction-heating coil; and a moving device of the preheating ring that moves the preheating ring between a heat position in which the preheating ring is induction-heated around an upper end of the lower silicon seed rod by the induction-heating coil and a wait position which is distant from the heat position.
1. A manufacturing method of silicon seed rod joining two silicon seed rods into one long silicon seed rod by welding, comprising the steps of:
disposing an upper silicon seed rod and a lower silicon seed rod vertically in a chamber so as to face a lower end of the upper silicon seed rod and an upper end of the lower silicon seed rod each other;
arranging an induction-heating coil around the lower end of the upper silicon seed rod;
heating the upper end of the lower silicon seed rod to glow by a preheating ring which is disposed below the induction-heating coil and is induction-heated;
elevating the lower silicon seed rod so as to transfer heat from the glowing lower silicon seed rod to the lower end of the upper silicon seed rod so that the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod glow;
melting the glowing lower end of the upper silicon seed rod and the glowing upper end of the lower silicon seed rod by induction-heat of the induction-heating coil in a state in which a gap is made between the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod;
bringing the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod into contact with each other in molten state; and
cooling the upper silicon seed rod and the lower silicon seed rod so that the upper silicon seed rod and the lower silicon seed rod are welded together.
2. The manufacturing method of silicon seed rod according to claim 1 , further comprising the step of keeping the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod in contact with each other in molten state for a prescribed period before cooling.
3. The manufacturing method of silicon seed rod according to claim 2 , further comprising the step of further elevating the lower silicon seed rod after keeping the upper silicon seed rod and the lower silicon seed rod in contact with each other for a prescribed period so as to press molten parts of the silicon seed rods with each other so that the molten parts radially swell out and cooling.
4. The manufacturing method of silicon seed rod according to claim 2 , wherein while keeping the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod in contact with each other in molten state for a prescribed period, the lower silicon seed rod is further rotated around an axis of the lower silicon seed rod.
5. The manufacturing method of silicon seed rod according to claim 1 , wherein when transferring the heat from the lower silicon seed rod to the upper silicon seed rod, the lower end of the upper silicon seed rod and the upper end of the lower silicon seed rod are in contact with each other.