Research On Smelting Process Of Cr12Steel By Vacuum Induction Furnace

Vacuum induction smelting is an significant method to smelt and refine steel. Because it creates excellent degassing environment, which is able to expel hydrogen, nitrogen and oxygen. Besides, vacuum condition both averts molten steel from oxidization and exerts enough electromagnetic stirring to molten steel. However, molten steel is in touch with crucible and crucible decomposes under high-temperature or vacuum condition during vacuum induction smelting, which might pollute molten steel to some degree.According to thermodynamic calculates, under a given condition, such as a specific temperature, vacuum degree and oxygen content in molten steel, two kinds of crucibles are both probable to decompose and expel oxygen into molten steel. The trend of decomposition increases with the rise of temperature and vacuum degree, while decreases with the rising content of dissolved oxygen. At a certain temperature and vacuum degree, thermal and chemical stability of CaO crucible are better than those of MgO crucible.In this article, MgO and CaO crucibles are used in the experiments to study carbon deoxidization of molten steel and thermal decomposition of crucibles. The researches reveal that thermal decomposition of crucibles can be reduced or avoided at properly low smelting temperature and vacuum degree, thus provides less oxygen into molten steel. If oxygen content in molten steel is higher than the equilibrium oxygen content for decomposition of crucible, vacuum degree should be improved to expel generated gas during reaction, which can decrease oxygen content in steel. Besides, CaO crucible with excellent thermostability and high vacuum degree can lead to the total oxygen content less than6×10-4%.Bottom blowing of Ar during vacuum induction smelting is functional of absorbing N at bubble interface Stronger stirring of molten steel during smelting can enlarge mass transfer coefficient of N in molten steel. The above methods are both able to accelerate denitriding process. Low vacuum degree and proper refining temperature is the key to lower N content of steel. Mobility of slag ought to be improved in order that gas is easily expelled from molten steel during top-slag smelting process.