Regulating the carbon potential in a gas carburizing atmosphere with natural gas as the enriched gas, by using O-2 and CO2 sensors

The gas-carburizing atmosphere for surface treatment of steel can be regula ted using the carbon potential (CP) which is obtained by measuring dew poin t, O-2 concentration or CO2 concentration. Since zirconium oxide O-2 sensor s are easier-to-handle and respond better than others, they are generally u sed when measuring O-2 concentrations. Methane is the main component of nat ural gas and is stable at high temperatures, so that traces of it tend to r emain in furnaces. The remaining methane decomposes on the O-2 sensor tip, and the O-2 concentration around the sensor tip decreases. Therefore the me asurement of carbon potential with O-2 sensors has been considered to be di fficult, when natural gas is used as the enriched gas. In this study, carbo n potential control using O-2 sensors for gas-carburizing atmospheres enric hed with natural gas, was examined. A new method for regulating CP was also examined. It utilizes the difference between CP calculated from the CO2 co ncentration and that calculated from the O-2 sensor value, while preventing sooting. With these methods for regulating the gas-carburizing atmosphere, seasoning time and gas consumption could be reduced.