A chilled mirror dew point measurement system for assessment of decarburisation furnace atmosphere

Abstract
A chilled mirror dew point instrument has been produced by European Electrical Steels to measure the dew point temperature of the decarburising furnace gas used during the processing of grain oriented electrical steel. Dew point measurement of this gas is difficult because of it's high humidity and corrosive nature. The instrument employs a novel sensor and well designed gas sampling system to ensure a low maintenance operation. A laboratory calibration unit was used to compare the new dew point instrument with a commercial chilled mirror system, which proved that the developed instrument was capable of measuring the dew point temperature with a tolerance of ±0.3°C. The instrument has been under evaluation on a production line for a period of eighteen months and has required very little maintenance. It has shown good correlation between changes in the furnace dew point temperature and the strip surface oxygen levels. In addition the system has indicated changes in dew point temperature when different thickness steel strip is processed.