Cgi cast iron and production method for the same

Abstract

The present invention relates to cast iron, and more particularly, to a compacted graphite iron (CGI) cast iron having an improved casting property, stable tensile strength and yield strength, and hardness in an appropriate range, by being produced with the amounts of carbon (C), silicon (Si), manganese (Mn), copper (Cu), tin (Sn), and magnesium (Mg) controlled, and a production method thereof.

1 . A cast iron for use with a cylinder block of an engine comprising:
 carbon (c) of 3.65 to 3.75 wt %;   silicon (Si) of 2.0 to 2.25 wt %;   manganese (Mn) of 0.3 to 0.6 wt %;   copper (Cu) of 1.2 to 1.4 wt %;   tin (Sn) of 0.07 to 0.10 wt %;   magnesium (Mg) of 0.008 to 0.018 wt %;   phosphorus (P) of 0.04 wt % or less;   sulfur (S) of 0.02 wt % or less; and   the balance of ferrum (Fe), an the entire weight   
     
     
         2 . The cast iron of  claim 1 , wherein tensile strength is 500 to 600 MPa. 
     
     
         3 . The cast iron of  claim 1 , wherein yield strength is 350 to 450 MPa. 
     
     
         4 . The cast iron of  claim 1 , wherein carbon equivalent is 4.35 to 4.5. 
     
     
         5 . The cast iron of  claim 1 , wherein nodularity of graphite produced by the carbon is 5 to 20%. 
     
     
         6 . A method of producing cast iron, comprising:
 producing original molten cast iron by melting a cast iron material, which contains carbon (C) of 3.65 to 3.75 wt %, silicon (Si) of 2.0 to 2.25 wt %, manganese (Mn) of 0.3 to 0.6 wt %, phosphorous (P) of above 0 and 0.04 wt % less, sulfur (S) of above 0 and 0.02 wt % or less, and the balance of ferrum (Fe), in the entire weight, in a furnace;   providing copper (Cu) of 1.2 to 1.4 wt %, tin (Sn) of 0.07 to 0.10 wt %, and magnesium (Mg) of 0.008 to 0.018 wt % in a ladle that is a container for tapping the original molten cast iron melted in a furnace;   producing molten cast iron by tapping the produced original molten cast iron with the ladle with copper (Cu) of 1.2 to 1.4 wt %, tin (Sn) of 0.07 to 0.10 wt %, and magnesium (Mg) of 0.008 to 0.018 wt %;   determining the amount of magnesium to be added by checking the content of magnesium contained in the molten cast iron in the ladle;   adding magnesium of which the amount to be added is determined to the molten cast iron in the ladle; and   injecting the molten cast iron added with the magnesium into a mold.   
     
     
         7 . The method of  claim 6 , wherein carbon equivalent in the original molten cast iron is 4.35 to 4.5. 
     
     
         8 . The method of  claim 6 , wherein the tapping temperature is adjusted to be 1,520° C. 
     
     
         9 . The method of  claim 6 , wherein magnesium is added by using a wire type of magnesium in the adding of magnesium.