Cast iron alloy with good oxidation resistance at high temperatures

Abstract

A cast iron alloy for cast iron products characterized by a high oxidation stability at surface temperatures of 800° C. to 950° C., comprising the chemical components 2.8 to 3.6% C by weight; 2.0 to 3.0% Si by weight; 2.5 to 4.3% Al by weight; up to 1.0% Ni by weight; up to 0.8% Mo by weight; up to 0.3% Mn by weight; 0.002 to 0.1% Ce by weight; 0.023 to 0.06% Mg by weight; up to 0.01% S by weight, residual Fe, and the usual impurities.

1 - 12 . (canceled) 
   
   
       13 . A cast iron alloy for cast iron products having high oxidation resistance at surface temperatures of from 800 to 950° C., comprising:
 from 2.8 to 3.6 wt % C;   from 2.0 to 3.0 wt % Si;   from 2.5 to 4.3 wt % Al;   up to 1.0 wt % Ni;   up to 0.8 wt % Mo;   up to 0.3 wt % Mn;   from 0.002 to 0.1 wt % Ce;   from 0.023 to 0.06 wt % Mg;   up to 0.01 wt % S; and   remainder Fe and impurities.   
   
   
       14 . The cast iron alloy as claimed in  claim 13 , wherein the alloy comprises:
 from 0.1 to 1 wt % Ni;   from 0.4 to 0.8 wt % Mo; and   up to 1.0 wt % Cr.   
   
   
       15 . The cast iron alloy as claimed in  claim 13 , wherein the temperature of the transition from the ferritic phase to the austenitic phase of the alloy lies above 880° C. 
   
   
       16 . The cast iron alloy as claimed in  claim 13 , wherein the alloy has a thermal expansion, as measured by a dilatometer, which varies uniformly and constantly up to a temperature of 880° C. 
   
   
       17 . The cast iron alloy as claimed in  claim 13 , wherein the alloy has a thermal expansion coefficient of from 8 to 12 10 −6 /K at 25° C. and from 13.5 to 15.5 10 −6 /K at 900° C. 
   
   
       18 . The cast iron alloy as claimed in  claim 13 , wherein the alloy has strength values of:
 from 500 to 650 MPa for tensile strength R m ;   from 470 to 620 MPa for yield point R p0.2 ; and   from 2.0 to 4.0 for elongation at break A 5 .   
   
   
       19 . The cast iron alloy as claimed in  claim 13 , wherein the alloy has a Brinell hardness of from 220 to 250. 
   
   
       20 . The cast iron alloy as claimed in  claim 13 , wherein the alloy has a thermal conductivity of from 20 to 25 W/mK at 25° C. and a thermal conductivity of from 23 to 29 W/mK at 900° C. 
   
   
       21 . A method for producing a cast iron alloy comprising:
 from 2.8 to 3.6 wt % C;   from 2.0 to 3.0 wt % Si;   from 2.5 to 4.3 wt % Al;   up to 1.0 wt % Ni;   up to 0.8 wt % Mo;   up to 0.3 wt % Mn;   from 0.002 to 0.1 wt % Ce;   from 0.023 to 0.06 wt % Mg;   up to 0.01 wt % S;   remainder Fe and impurities;   
     comprising the steps of:
 treating the alloy in a magnesium converter to obtain a very low-sulfur alloy; and 
 after pretreatment in the magnesium converter, casting the alloy into a mold without any subsequent heat treatment. 
 
   
   
       22 . The method as claimed in  claim 21 , including forming the alloy into one of an exhaust manifold and a turbocharger housing for automobile manufacture.