Atmospheres for decarburize annealing steels
AssigneeAir Products and Chemicals, Inc.
InventorsDiwakar Garg, Brian B. Bonner, Kerry R. Berger
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Abstract
A process for producing low-cost atmospheres suitable for decarburize annealing carbon steels from non-cryogenically generated nitrogen containing up to 1.54 residual oxygen by catalytically deoxygenating a non-cryogenically generated nitrogen stream at low temperatures with a hydrocarbon gas and mixing the deoxygenated stream with an economical amount of hydrogen prior to introduction into the furnace for annealing. The process includes the use of 1) hydrocarbon gas to convert residual oxygen to a mixture of carbon dioxide and moisture at low temperatures and 2) mixing the deoxygenated stream with a sufficient amount of hydrogen to maintain a pH.sub.2 /pH.sub.2 O ratio of at least 2 in the furnace.
Claims14
A method for producing an atmosphere inside a furnace maintained at a temperature for decarburized annealing carbon steels, comprising the steps of:
- pre-heating non-cryogenically produced nitrogen gas containing between 0.2 and 2% by volume residual oxygen to a temperature of at least 200.degree. C.;
- mixing said pre-heated non-cryogenically produced nitrogen with more than a stoichiometric amount of a hydrocarbon gas required to convert oxygen in said nitrogen to a mixture of moisture and carbon dioxide;
- passing said mixture through a bed of precious metal catalyst for conversion of said oxygen to form an effluent gas containing nitrogen, unreacted hydrocarbon gas, moisture, carbon dioxide, and less than 10 ppm oxygen;
- mixing said effluent with hydrogen in an amount to provide a pH.sub.2 /pH.sub.2 O of at least 2 inside said furnace when said effluent mixed with hydrogen is introduced into said furnace.
Dependencies are inferred from the claim text.