DEVELOPMENT AND TEST-PERFORMANCE OF NEEDL E SENSORS TO DETERMINE OXYGEN IN METALLIC MELTS BELOW 1000-DEGREES-C

Oxide ceramic sensors ore being used to determine oxygen in metallic m elts. These sensors are designed as tubular sensors and have gained im portance in industrial practice. The oxygen content is obtained not on ly in situ but also for concentrations below those of usual chemical a nalysis. In contrast to chemical analysis, electrochemical sensors ind icate dissolved oxygen in melts instead of the total oxygen content. T herefore both analysis methods complete themselves. The production of tubular sensors is comlicated and cost-intensive. Therefore efforts ar e made to manufacture these sensors using alternative techniques and m ore reasonably priced materials. The needle sensor represents a possib le further development. The advantage in comparison with the tubular s ensor consists in the miniaturization of the functional layers. The de velopment is combined with an improvement of the temperature shock res istance and a comparatively low material consumption depending on the production method. The needle sensors used in this work were manufactu red using thermal spraying techniques. The contact leeds of the sensor s consisted of conventional heat and corrosion resistant metals or met allic alloys. An excellent test performance of the needle sensors has been achieved in lead and tin melts at temperatures between 500 and 80 0 degrees C.