Process for Producing a High-Cleanliness Steel

Abstract

A process for producing a high-cleanliness steel which can produce, without relying upon a high-cost remelting process, steel products having cleanliness high enough to satisfy requirements for properties of mechanical parts used under severe environmental conditions. The production process comprises the steps of: transferring a molten steel produced in an arc melting furnace or a converter to a ladle furnace to refine the molten steel; subjecting the molten steel to circulation-type degassing; and casting the molten steel into an ingot, wherein, in transferring the molten steel to the ladle furnace, a deoxidizer including aluminum and silicon, is added to previously deoxidize the molten steel, that is, to perform tapping deoxidation before refining in the ladle refining furnace.

1 . A process for producing a high-cleanliness steel, comprising the steps of: transferring a molten steel produced in an arc melting furnace or a converter to a ladle furnace to refine the molten steel; degassing the molten steel; and then casting the molten steel into an ingot, said process further comprising the step of tapping deoxidation wherein, in transferring the molten steel to the ladle furnace, a deoxidizer including manganese, aluminum, and silicon is added to the molten steel by previously placing the deoxidizer in the ladle, and/or by adding the deoxidizer to the molten steel in the course of tapping into the ladle, whereby the molten steel is pre-deoxidized before the refining in the ladle furnace. 
     
     
         2 . The process according to  claim 1 , wherein the molten steel is transferred to the ladle furnace in such a manner that the tapping temperature of the molten steel is at least 100° C. above the melting point of the steel. 
     
     
         3 . The process according to  claim 1 , wherein the refining in the ladle furnace is carried out for not more than 60 min, and the degassing is carried out for not less than 25 min.