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: subjecting a molten steel to oxidizing refining in an arc melting furnace or a converter; adding a deoxidizer to the molten steel in the furnace before tapping to deoxidize the molten steel; transferring the deoxidized molten steel to a ladle furnace to perform ladle refining; and then circulating the refined molten steel through a circulation-type vacuum degassing device to degas the molten steel. 
     
     
         2 . The process according to  claim 1 , wherein the molten steel is transferred to the ladle furnace in such a manner that the temperature of the molten steel to be transferred 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 in the circulation-type vacuum degassing device is carried out for not less than 25 min.