Source: Super Systems, Inc.
Achieving the elimination of oxidation during thermal treatment has driven heat treaters for decades and resulted in a wide variety of approaches. The obvious method is to flow an inert gas such as nitrogen into the furnace in order to drive out both air and moisture. By itself, however, this technique is inadequate.
The zirconia carbon sensor has been used for nearly three decades to control the carbon potential in many carburizing applications. Today’s best of the web article examines the use of the zirconia carbon sensor in a variety of annealing and special treatment applications and considers how the sensor millivolt output is preferred because it relates directly (not empirically) to the free oxygen concentration in the surrounding environment.
An Excerpt:
“While it is desirable to avoid oxidation during thermal treatment, the achievement of adequate control using one of the ‘getter’ gases requires that the sensor millivolts achieved be established at some value higher than the vee formed by the iron reaction at temperatures below 1375ºF and the carbon reaction above that temperature. The vee will demonstrate the lower limit, but the practical level should be established by evaluation of product quality, getter cost and possible sooting. The appropriate level will be limited by such things as furnace leaks, atmosphere agitation, work porosity, time of treatment, etc.”
Read the entire article from Super Systems, Inc., by clicking here: “Precise Control of Protective Atmospheres“
