Process for producing cast steel billet or steel ingot of titanium-added case hardening steel

Abstract

Disclosed is a production process that can suppress the formation of large-diameter TiN or N-rich TiCN inclusions which adversely affect machinability and consequently can produce a cast steel billet or steel ingot or a steel material of a Ti-added case hardening steel having excellent machinability. The production process comprises the step of casting a steel comprising by weight carbon (C): 0.10 to 0.30%, titanium (Ti): 0.05 to 0.20%, and nitrogen (N): not more than 0.0100% into a round cast steel billet or steel ingot having a diameter of not more than 23 cm or, in the alternative, a rectangular cast steel billet or steel ingot having a short side length of not more than 23 cm.

1 . A process for producing a cast steel billet or steel ingot of a titanium (Ti)-added case hardening steel, said process comprising the steps of: 
 melting a steel comprising by weight carbon (C): 0.10 to 0.30%, titanium (Ti): 0.05 to 0.20%, and nitrogen (N): not more than 0.0100%; and    casting the molten steel into a round cast steel billet or steel ingot having a diameter of not more than 23 cm.    
   
   
       2 . The process according to  claim 1 , wherein said steel comprises by weight 
 carbon (C): 0.10 to 0.30%,    silicon (Si): 0.03 to 1.00%,    manganese (Mn): 0.20 to 1.00%,    phosphorus (P): not more than 0.025%,    sulfur (S): 0.001 to 0.030%,    nitrogen (N): not more than 0.100%,    titanium (Ti): 0.05 to 0.20%,    aluminum (Al): 0.003 to 0.050%,    oxygen (O): not more than 0.0030%,    one or more of chromium (Cr): 0.15 to 2.00%, nickel (Ni): 0.10 to 2.00%, molybdenum (Mo) 0.03 to 0.30%, boron (B): 0.0001 to 0.0020%, vanadium (V): 0.01 to 0.20%, and niobium (Nb): 0.01 to 0.15%, and    the balance iron (Fe) and unavoidable impurities.    
   
   
       3 . A process for producing a cast steel billet or steel ingot of a titanium (Ti)-added case hardening steel, said process comprising the steps of: 
 melting a steel comprising by weight carbon (C): 0.10 to 0.30%, titanium (Ti): 0.05 to 0.20%, and nitrogen (N): not more than 0.0100%; and    casting the molten steel into a rectangular cast steel billet or steel ingot having a short side length of not more than 23 cm.    
   
   
       4 . The process according to  claim 3 , wherein said steel comprises by weight 
 carbon (C): 0.10 to 0.30%,    silicon (Si): 0.03 to 1.00%,    manganese (Mn): 0.20 to 1.00%,    phosphorus (P): not more than 0.025%,    sulfur (S): 0.001 to 0.030%,    nitrogen (N): not more than 0.0100%,    titanium (Ti): 0.05 to 0.20%,    aluminum (Al): 0.003 to 0.050%,    oxygen (O): not more than 0.0030%,    one or more of chromium (Cr): 0.15 to 2.00%, nickel (Ni): 0.10 to 2.00%, molybdenum (Mo) 0.03 to 0.30%, boron (B): 0.0001 to 0.0020%, vanadium (V): 0.01 to 0.20%, and niobium (Nb): 0.01 to 0.15%, and    the balance iron (Fe) and unavoidable impurities.