| 摘要 |
PROBLEM TO BE SOLVED: To reduce a hot rolling time and to extend a tool life. SOLUTION: A ceramic plug for hot working, of which the contact face with a stock material is made of a ceramic, has a glass coated layer formed on the contact face. The glass having the softening point of 500-1500 deg.C is coated in thickness of 10-5000μm. In piercing, the glass coated layer is softened by the heat of a heated stock material so as to exhibit a lubrication function. As compared to the plug not having the coated layer, the friction resistance to the stock material to be brought into contact is reduced, thus the piercing is smoothly done.
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