Austenite heat-resistant spheroidal graphite cast iron

Abstract

A heat-resistant, austenitic spheroidal graphite cast iron has a composition comprising 1-4.5% by weight of Mo, and 0.001-0.5% by weight of Sn and/or Sb as (2Sn+Sb). It preferably has a composition comprising 1-3.5% of C, 1-6.5% of Si, 3% or less of Cr, 10-40% of Ni, 1-4.5% of Mo, 0.001-0.5% of Sn and/or Sb as (2Sn+Sb), and 0.1% or less of a graphite-spheroidizing element, on a weight basis.

1 . A heat-resistant, austenitic spheroidal graphite cast iron comprising 1-4.5% by weight of Mo, and 0.001-0.5% by weight of Sn and/or Sb as (2Sn+Sb).  
   
   
       2 . The heat-resistant, austenitic spheroidal graphite cast iron according to  claim 1 , wherein it has a composition comprising 1-3.5% of C, 1-6.5% of Si, 3% or less of Cr, 10-40% of Ni, 1-4.5% of Mo, 0.001-0.5% of Sn and/or Sb as (2Sn+Sb), and 0.1% or less of a graphite-spheroidizing element, on a weight basis.  
   
   
       3 . The heat-resistant, austenitic spheroidal graphite cast iron according  claim 1 , wherein it further comprises 0.3% or less by weight of N.  
   
   
       4 . The heat-resistant, austenitic spheroidal graphite cast iron according to  claim 1 , wherein it has room-temperature elongation of 2% or more, weight loss by oxidation of 30 mg/cm 2  or less when kept at 950° C. for 200 hours in the air, and 0.2−% yield strength of 55 N/mm 2  or more at 950° C. in the air.  
   
   
       5 . The heat-resistant, austenitic spheroidal graphite cast iron according to  claim 1 , wherein it has a thermal fatigue life of 400 cycles or more in a thermal fatigue test of heating and cooling at the highest temperature of 950° C., a temperature amplitude of 800° C. and a constraint ratio of 0.5.  
   
   
       6 . The heat-resistant, austenitic spheroidal graphite cast iron according to  claim 1 , wherein it has an average thermal expansion coefficient of 18×10 −6 /° C. or less in a range from room temperature to 1000° C.