Systems and methods for monitoring or controlling the ratio of hydrogen to water vapor in heat metal treating atmospheres
Systems and methods for monitoring a heat treating atmosphere derive from at least one sensor placed in situ in the atmosphere a process variable, which is indicative of the ratio of gaseous hydrogen H 2 (g) to water vapor H 2 O (g) in the atmosphere. The systems and methods use the process variable, e.g., to control the atmosphere, or to record or display the process variable.
1. A heat treating system comprising
a heat treating furnace,
an atmosphere source for supplying a preselected gas atmosphere to the furnace,
a heat source to maintain the preselected gas atmosphere inside the furnace at a preselected temperature not greater than a temperature at which wustite (FeO) forms,
an oxygen sensor located in situ in the furnace in contact with the preselected gas atmosphere, the oxygen sensor providing a first electrical input that varies according to oxygen content of the preselected atmosphere,
a temperature sensor located in situ in the furnace in contact with the preselected gas atmosphere, the temperature sensor providing a second electrical input that varies according to temperature of the preselected atmosphere, and
a processor to generate a computed ratio of gaseous hydrogen H 2 (g) to water vapor H 2 O (g) for the preselected atmosphere as a function of the first and second electrical inputs.
2. A system according to claim 1
and further including an output for the computed ratio.
3. A system according to claim 2
wherein the output is coupled to a device for displaying the computed ratio.
4. A system according to claim 2
wherein the output is coupled to a device for recording the computed ratio.
5. A system according to claim 2
wherein the output is coupled to a controller for the atmosphere source.
6. A system according to claim 1
wherein the processor includes an atmosphere control function comprising a comparator to compare the computed ratio to a selected set point and generate a deviation, and
further including an output for the deviation.
7. A system according to claim 6
wherein the output is coupled to a controller for the atmosphere source.
8. A system according to claim 1
wherein the heat treating atmosphere comprises an H 2 /N 2 atmosphere.
9. A system according to claim 1
wherein the heat treating atmosphere contains CO, CO 2 , H 2 , and H 2 O.
10. A system according to claim 1
wherein the heat treating atmosphere comprises a steam atmosphere.