Probe for continuously regulating the gaseous atmosphere in nitriding or nitrocarburizing processes in atmospheric or low pressure ovens

摘要

At least one module connects the sampler to the furnace (3), a first module (5) measures the residual hydrogen in the furnace gas, a cracking module (7) for the residual ammonia in the furnace gas, a second module (9) measures the total residual hydrogen, and a blowing module (10) uses the Venturi effect and is connected to a mass flow meter (3') for the gas blown into the furnace Sampler (1) for continuously regulating the composition of the gaseous atmosphere during a nitration or nitrocarburation process in atmospheric or low pressure furnaces. In the case of nitrocarburation with an oxidant gas, the sampler includes two modules for measuring the partial pressure of the oxygen (6, 8) placed respectively upstream and downstream of the cracking module. The modules are arranged so the sampler measures the furnace atmosphere in a closed circuit. The module connecting the sampler to the furnace is a sampling tube (11) connecting the furnace to the first module for measuring residual hydrogen and a return pipe (12) connecting the blowing module to the furnace. The blowing module is a blowing pipe (27) opening into the return pipe employing the Venturi effect by means of an injector (26) and an inlet (22) for injection of nitrogen. The mass flow meter includes at least two temperature detectors (15, 17) and a heater (16) and acts in cooperation with a regulator controlling the nitrogen injection. The sampler also contains a calibration module (4) downstream of the connecting module and including at least two valves (18, 19) and two inlets of calibration gas (20, 21) placed respectively on the sampling tube and the return pipe. The valves have motorized control units. The modules for measuring the partial pressure of oxygen each comprise a Lambda detector. The sampler also includes means of heating and of controlling the temperature precisely to a temperature above 100 deg. C. The sampler is connected to a calculator calculating the nitration potential KN or the carbon activity.