Cast irons for high temperature use

Abstract

Cast irons are provided which have no intentional addition of molybdenum (Mo) and which have compositions with additional silicon that provide certain advantages, such as lower cost, higher use temperatures, and increased tensile strength, over conventional Mo-bearing cast irons. In the cast irons, Mo is absent or present only as an impurity element.

1 . A cast iron wherein Si is present in an amount of about 3.5 weight % to about 6.0 weight % and wherein Mo is absent or present as an impurity element. 
     
     
         2 . The cast iron of  claim 1  wherein Si is about 4.5% to about 6.0%. 
     
     
         3 . The cast iron of  claim 2  wherein Si is about 4.75% to about 5.5%. 
     
     
         4 . The cast iron of  claim 1  which a nodular cast iron. 
     
     
         5 . A cast iron that consists essentially of, in weight %, about 2.0% to about 4.0% C, about 3.5% to about 6.0% Si, and balance Fe wherein Mo is absent or present as an impurity element. 
     
     
         6 . The cast iron of  claim 5  wherein Mo does not exceed about 0.01 weight % of the cast iron. 
     
     
         7 . The cast iron of  claim 5  wherein Si is about 4.5% to about 6.0%. 
     
     
         8 . The cast iron of  claim 7  wherein Si is about 4.75% to about 5.5%. 
     
     
         9 . The cast iron of  claim 5  wherein C is about 2.5% to about 3.5%. 
     
     
         10 . The cast iron of  claim 5  having an AC 1  temperature of about 880 degrees C. and above. 
     
     
         11 . The cast iron of  claim 5  including Mg and/or Ce as a nodularizing agent. 
     
     
         12 . The cast iron of  claim 5  having an ultimate tensile strength above about 90 ksi at 23 degrees C. 
     
     
         13 . The cast iron of  claim 12  having an ultimate tensile strength above about 30 ksi at 600 degrees C. 
     
     
         14 . A cast iron having a composition, in weight %, consisting essentially of about 2.0% to about 4.0% C, about 3.5% to about 6.0% Si, up to about 2.0% Cr, up to about 2.0% Mn, up to about 0.75% Ni, up to about 2.5% W, up to about 2.5% Cu, up to about 1.0% V up to about 1.0% Ti, effective amount of a nodularizing agent, and balance Fe wherein Mo is absent or present as an impurity element. 
     
     
         15 . The cast iron of  claim 14  wherein Mo does not exceed about 0.01 weight % of the cast iron. 
     
     
         16 . The cast iron of  claim 14  including about 0.01% to about 0.10% Mg as a nodularizing agent. 
     
     
         17 . The cast iron of  claim 14  wherein Si is about 4.5% to about 6.0%. 
     
     
         18 . The cast iron of  claim 17  wherein Si is about 4.75% to about 5.5%. 
     
     
         19 . The cast iron of  claim 14  having one or more of Cu, W, V, or Ti present in a respective amount of about 0.25% to about 2.5% for Cu, about 0.25% to about 2.5% for W, about 0.025% to about 0.2% for V, or about 0.1% to about 0.25% for Ti. 
     
     
         20 . The cast iron of  claim 14  having an AC 1  temperature of about 880 degrees C. and above. 
     
     
         21 . The cast iron of  claim 14  having nominally about 3 weight % graphite content in its cast microstructure. 
     
     
         22 . The cast iron of  claim 14  having an ultimate tensile strength above 90 ksi at 23 degrees C. 
     
     
         23 . The cast iron of  claim 22  having an ultimate tensile strength above about 30 ksi at 600 degrees C. 
     
     
         24 . A Mo-free cast iron nominally consisting essentially of, in weight %, about 3.0% C, about 5.0% Si, about 0.03% Cr, about 0.5% Mn, about 0.03% Ni, about 0.3 to about 0.5% W, an effective amount of Mg for nodularization, and balance Fe. 
     
     
         25 . A Mo-free cast iron nominally consisting essentially of, in weight %, about 3.0% C, about 5.0% Si, about 0.03% Cr, about 0.5% Mn, about 0.03% Ni, about 0.3 to about 0.5% W, about 0.4 to about 0.5% Cu, an effective amount of Mg for nodularization, and balance Fe. 
     
     
         26 . A Mo-free cast iron nominally consisting essentially of, in weight %, about 3.0% C, about 5.0% Si, about 0.03% Cr, about 0.03 to about 0.05% Mg, about 0.5% Mn, about 0.03% Ni, about 1.0 to about 1.5% W, an effective amount of Mg for nodularization, and balance Fe. 
     
     
         27 . A Mo-free cast iron nominally consisting essentially of, in weight %, about 3.0% C, about 5.0% Si, about 0.03% Cr, about 0.5% Mn, about 0.03% % Ni, about 0.3 to about 0.5% W, about 0.4 to about 0.5% Cu, about 0.1% of each of V and/or Ti, an effective amount of Mg for nodularization, and balance Fe. 
     
     
         28 . A component of an internal combustion engine made of the cast iron of  claim 1 . 
     
     
         29 . The component of  claim 28  which is an exhaust manifold.