Cast iron alloy containing boron

Abstract

The alloy of ductile cast iron to which boron has been added is found to have improved annealability as compared to a non-boron treat ductile iron. The addition of boron in amounts between about 10 ppm and 150 ppm by weight effectively combines with nitrogen dissolved in the molten iron and thus serves to minimize the influence of nitrogen on the stability of carbides and pearlite and also forms BN, which can serve as nuclei for the precipitation of graphite.

1 . A ductile cast iron alloy, comprising: 
 between about 2.0 and 4.0 percent carbon    between about 1.5 and 4.0 percent silicon    between about 0.1 and 1.5 percent manganese    between about 0.0005 and 0.05 percent sulfur    between about 0.01 and 0.05 percent magnesium    between about 10 and 150 ppm boron; and    a balance of up to 100 percent of iron and other incidental residual elements.    
   
   
       2 . A ductile cast iron alloy as defined in  claim 1 , wherein the boron content is between 40 ppm and 80 ppm.  
   
   
       3 . A ductile cast iron alloy as defined in  claim 1 , wherein the anealability of primary carbides is improved over ductile cast iron alloy without a boron content of between 10 and 150 ppm.  
   
   
       4 . A ductile cast iron alloy as defined in  claim 1 , wherein the anealability of pearlite is improved over ductile cast iron alloy without a boron content of between 10 and 150 ppm.  
   
   
       5 . A ductile cast iron alloy as defined in  claim 1 , wherein the percentage of ferrite in non-chill cast articles of the alloy is increased over ductile cast iron alloy without a boron content of between 10 and 150 ppm.  
   
   
       6 . A ductile cast iron alloy as defined in  claim 1 , wherein the nodule count as an area ratio is increased over ductile cast iron alloy without a boron content of between 10 and 150 ppm.  
   
   
       7 . A ductile cast iron alloy as defined in  claim 6 , wherein the nodule count is increased between 20 and 35%.