| 摘要 |
PURPOSE: A vacuum nitrogen solution process is provided to improve hardness and strength by dissolving nitrogen on the surface of stainless steel in a vacuum atmosphere, and to prevent exhaustion of chromium through the production inhibition and the morphology control of chromium carbide or chromium nitride. CONSTITUTION: The vacuum nitrogen solution process comprises a passivation layer removing step of removing a passivation layer formed on the surface of the steel product by heating a steel product containing elements having strong chemical affinity with nitrogen to the austenitic temperature range of 1000 deg.C or more in a vacuum furnace so that an internal pressure of the vacuum furnace is maintained to 0.01 torr or less for more than 30 minutes; a nitrogen solution step of injecting nitrogen gas into the vacuum furnace, thereby maintaining an internal pressure of the vacuum furnace to 760 torr(1 atmospheric pressure) or more for more than two hours as maintaining the passivation layer removed steel product at the austenitic temperature range of 1000 deg.C or more so that nitrogen elements are dissolved onto the surface of the steel product by permeating and diffusing nitrogen gas in a molecular phase deep into the surface of the steel product in a depth of about 0.5 to 2 mm; and a cooling step of pressurizing and rapidly cooling using nitrogen gas by simultaneously operating the cooler and the circulation fan to circulate the nitrogen gas after moving the nitrogen element dissolved steel product into a cooling chamber in which a cooler comprising a refrigerant pipe and a circulation fan are installed and injecting a nitrogen gas of an ordinary temperature into the cooling chamber in a pressure of 1 kg/mm¬2 or more, wherein the nitrogen dissolved steel product is tempered at a temperature of 600 deg.C or less so that nitrides deposited on the surface of the steel product are controlled in a shape of M2N.
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