| 摘要 |
PURPOSE:To make a crack hard to be generated on an alumina insulation film layer while having a long life before burn-out of a core by performing sintering of the almina layer firstly in a hydrogen atmosphere at about 1,550-1,850 deg.C and then in a vacuum furnace at about 1,100-1,550 deg.C. CONSTITUTION:An alumina layer being about 70mum thick is formed on a tungsten core by electrodeposition. Then, the alumina layer is sintered by being heated in a hydrogen atmosphere at 1,550-1,850 deg.C for about 5min. Next, this is heated in a vacuum furnace at 1,100-1,850 deg.C for about 1hr to finish a heater. The heater thus obtained has a tungsten core to which the alumina coating layer is firmly stuck thus making a crack hard to be generated on the alumina coating while having a long life before burn-out of the core.
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