| 摘要 |
<p>PURPOSE:To obtain a heater hard to generate a deformation and a crack and having the fine insulating pressure proof ability by specifying the particle size distribution of alumina grains of an insulating alumina layer coating a double- helically wound metal wire. CONSTITUTION:In an insulating alumina layer 3 coating a double-helically wound metal wire 2, purity of alumina grains is more than 99.8% and the mean grain diameter is within 7-12mum, and the alumina grains are mixed at the particle size distribution so that grains having a diameter more than 15mum and grains having a diameter less than 6m are respectively 10-30% and the residual is grains having a diameter within 6-15mum. Insulating pressure proof ability between a heater and a cathode is remarkably improved by using this heater, and the pressure proof defection caused by high working temperature of an impregnation type cathode can be prevented previously.</p> |
