| 摘要 |
<p>PURPOSE:To prevent a core from being rusted when water is infiltrated due to the damage of a plastic coating layer and to obviate the contamination of a sample by using a ceramic core or a core coated with a ceramic as the core of a plastic-coated ball. CONSTITUTION:A ceramic core 1 or a core 4 coated with a ceramic coating layer 5 is used as the core of a ball coated with a plastic 2. Consequently, when the ball is used, the ball is not rusted even if water, etc., are infiltrated. Since the ball is coated with the ceramic coating excellent in corrosion resistance, an increase in the amt. of impurities is minimized, and the purity of a mixed material is stably maintained for a long time.</p> |
