Decarbonization manner null of extremely low carbon chrome content

摘要

PURPOSE: To provide a reduced pressure treating method for executing efficient refining to an extremely low carbon range with a little chromium oxidizing quantity at the time of producing the extremely low carbon chromium-containing steel. ;CONSTITUTION: In a vacuum refining by dipping an immersion tube 2 into the molten steel in a ladle 1 and reducing the pressure in the immersion tube 2 and also supplying stirring gas from the bottom part of the ladle, to the molten steel having ≥5% Cr concn., gaseous oxygen is injected from the upper part at 0.04-0.40Nm³/Hr.cm² oxygen speed against the bubble active surface in the range of 1-0.02% carbon concn., and by stirring in the condition of making the bubble active surface to ≥10% of the whole surface of the molten steel and ≥100% oxygen blowing surface, the decarbonization restraining chromium oxidation to the extremely low carbon range can be executed. Further, thereafter, the pressure is returned back to the original condition and the immersion tube is pulled upward from the molten steel surface, and by charging alloys for reduction, the chromium oxide produced during decarbonizing can efficiently be recovered.;COPYRIGHT: (C)1993,JPO&Japio