Cast iron semi-finished product excellent in workability and method of production of the same

Abstract

The present invention provides tough cast iron and cast iron semi-finished products excellent in workability without heat treatment requiring massive heat energy and long time and a method of production enabling these to be efficiently produced, that is, cast iron of ingredients of white cast iron where particles of spheroidal graphite or flattened graphite are dispersed, cast iron where the ingredients of the white cast iron satisfy, by wt %, (% C)≦4.3−(% Si)÷3 and C≧1.7% and where the particles of spheroidal graphite are dispersed at a density of 50 particles/mm 2 or more, or cast iron where the particles of flattened graphite have a width of 0.4 mm or less and a length of 50 mm or less.

1 . A cast iron and a cast iron semi-finished product excellent in workability characterized by being comprised of cast iron of an ingredient system of white cast iron inside of which particles of spheroidal or flattened graphite with outside surfaces partially or completely covered with ferrite are dispersed independently or complexly. 
   
   
       2 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in at the particles of spheroidal graphite or flattened graphite are dispersed at a density of 50 particles/mm 2  or more. 
   
   
       3 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in that the particles of spheroidal graphite or flattened graphite have a width of 0.4 mm or less and a length of 50 mm or less. 
   
   
       4 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in that the ratio of the ferrite in the cast iron is 70% or more. 
   
   
       5 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in that the ingredients giving white cast iron are, by wt %, a composition satisfying (% C)≦4.3−(% Si)÷3 and C≧1.7%. 
   
   
       6 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 5 , characterized by further including as cast iron ingredients at least one of Cr≧0.1 wt % and Ni≧0.1 wt %. 
   
   
       7 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in that the particles of spheroidal or flattened graphite are bonded complexly with at least one type of particles of oxides, sulfides, nitrides, or their complex compounds containing at least one of Mg, Ca, and an REM. 
   
   
       8 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 7 , characterized in that the at least one type of particles of oxides, sulfides, nitrides, or their complex compounds have diameters of 0.05 to 5 μm. 
   
   
       9 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 1 , characterized in that said white cast iron semi-finished product is sheet cast iron, plate cast iron, or rail cast iron. 
   
   
       10 . A cast iron and a cast iron semi-finished product excellent in workability as set forth in  claim 9 , characterized in that said cast iron semi-finished product has a thickness of 1 to 400 mm. 
   
   
       11 . A method of production of a cast iron semi-finished product excellent in workability obtained by casting a melt of ingredients comprised of white cast iron to which a spheroidalization agent has been added and rolling the obtained cast semi-finished product. 
   
   
       12 . A method of production of a cast iron semi-finished product excellent in workability as set forth in  claim 11 , characterized in that said spheroidalization agent includes at least one of Mg, Ca, and an REM. 
   
   
       13 . A method of production of a cast iron semi-finished product excellent in workability as set forth in  claim 11 , characterized by further heat treating the rolled material.