Process for producing steel for high-carbon steel wire material with excellent drawability and fatique characteristics

Abstract

The present invention provides a method suitable for manufacturing a steel material for obtaining a steel wire rod with decreased amount of hard nonmetallic inclusions and improved drawability and fatigue property by adequately controlling the conditions of secondary refining and manufacturing conditions in a converter. Converter blowing is performed by taking molten iron, cold iron, and steel scrap as main raw materials to be charged into a converter, the ratio of these components based on all the main raw materials being such that the molten iron takes 96 to 100% (means wt. %, same hereinbelow), the cold iron takes 4% or less, and the steel scrap takes 2% or less, and by setting an average P concentration in all the main raw materials to 0.02% or less, and operations are carried out such that a flow rate of gas for stirring molten steel during secondary refining after completion of the converter blowing is set to 0.0005 Nm 3 /min or more to 0.004 Nm 3 /min or less per 1 t of molten steel, and then a flow rate of Ar used to purge the inside of a tundish in continuous casting is set to 0.04 Nm 3 /min or more to 0.10 Nm 3 /min or less per 1 t of molten steel within the tundish.

1 . A method for manufacturing steel for high-carbon steel wire rod that excels in drawability and fatigue property, characterized in that converter blowing is performed by taking molten iron, cold iron, and steel scrap as main raw materials to be charged into a converter, the ratio of these components based on all the main raw materials being such that the molten iron takes 96 to 100% (means wt. %, same hereinbelow), the cold iron takes 4% or less, and the steel scrap takes 2% or less, and by setting an average P concentration in all the main raw materials to 0.02% or less, and operations are conducted such that a flow rate of gas for stirring molten steel during secondary refining after completion of the converter blowing is set to 0.0005 Nm 3 /min or more to 0.004 Nm 3 /min or less per 1 t of molten steel, and then a flow rate of Ar used to purge the inside of a tundish in continuous casting is set to 0.04 Nm 3 /min or more to 0.10 Nm 3 /min or less per 1 t of molten steel within the tundish. 
     
     
         2 . The manufacturing method according to  claim 1 , wherein a chemical composition of the steel for steel wire rod comprises C: 0.4 to 1.3%, Si: 0.1 to 2.5%, Mn: 0.2 to 1.0%, and Al: 0.003% or less with Fe and unavoidable impurities as the balance. 
     
     
         3 . The manufacturing method according to  claim 1 , wherein the steel for steel wire rod further comprises as another element at least one element selected from the group consisting of Ni: 0.05 to 1%, Cu: 0.05 to 1%, and Cr: 0.05 to 1.5%. 
     
     
         4 . The manufacturing method according to  claim 1 , wherein the steel for steel wire rod further comprises as another element at least one element selected from the group consisting of Li: 0.02 to ppm, Mg: 0.02 to 20 ppm, Ce: 3 to 100 ppm, and La: 3 to 100 ppm.