Carburising atmosphere control in heat treatment furnaces - using measurement of temperature and oxygen level to determine carbon potential of atmosphere

摘要

Generation of indication and control signal for the carbon potential of the atmos. in a carburising heat treatment furnace involves the following features. The atmos. is generated by injection of a hydrocarbon gas and the O2 potential is monitored by a probe. A convenient signal valve is set at a carbon potential base level (Co) and a base operating temp. (To). The difference between the base temp. and the actual furnace temp. is multiplied by a constant factor and this value added to the value of the working point. A further signal (X) is added to this which corresponds to the eleviation between the actual carbon value (C) and the basic carbon value (Co). A quadratic relationship is established of the form X = a(C-Co)2. This is determined from the O2 potential by an O2 probe. The probe signal is then compared with the signal generated by addition and the value for C determined via a computer circuit. For monitoring the carburisation potential of heat treatment furnaces for cast iron workpieces. Allows the use of an O2 probe in a simple way to generate an indication and control signal to control the C level.