Ceramic heater insert or plug useful as preheating or ignition plug for heating and combustion units and diesel engines

摘要

The ceramic heater insert or plug contains a refractory metal resistance heating wire which has an anisotropic grain shape or which consists of pure tungsten containing no grain growth-inhibiting trace elements. The ceramic heater insert or plug consists of a refractory metal resistance heating wire element which is embedded in a ceramic material and which has a diameter of /}0.4 mm and a grain shape with a longitudinal to radial size ratio of 1.5-100, the radial grain size being >= 5 mu . Independent claims are also included for the following: (i) production of the above heater insert or plug by heat treating a refractory metal resistance heating wire at 1900-3000 deg C, embedding the wire in ceramic material and firing; (ii) a ceramic heater insert or heater plug consisting of a tungsten resistance heating wire element which is embedded in a ceramic material and which has >= 99.99% purity with no detectable contents of grain growth-inhibiting trace elements such as potassium, aluminum and silicon; and (iii) production of the above heater insert or plug (ii) by embedding the pure tungsten wire in ceramic material and hot pressing at 1700-2000 deg C. Preferred Features: The ceramic material may contain 5-25 vol.% molybdenum silicide.