| 摘要 |
PURPOSE:To prevent the failure of a head part owing to thermal expansion and to improve the durability thereof by providing plural relief grooves to an external screw part of a connecting rod and closing the aperture on the nozzle side of an internal screw hole in the head part with a refractory material. CONSTITUTION:Boron nitride constituting the head part 6a has good heat conductivity and therefore the external screw part 10a of the connecting rod 10 receives strongly the heat of a molten metal during the pouring operation and expands in the radial direction but part of the thermal expansion is absorbed by the respective relief grooves 12. The thermal expanding force of the external screw part 10a acting to the screwed part between the external screw part 10a and the head part 6a is thereupon decreased and the failure of the head part 6a is obviated. Since the nozzle side aperture 8a of the internal screw hole 8 in the head part 6a is held closed by the refractory material 13, the grooves 12 are prevented from being filled by the molten metal and the effect of preventing the failure of the heat part 6a by the grooves 12 is maintained. |
