Patent ID: 7794650

Claim:
A graphite-containing heat-resistant cast iron comprising Si and W, and having intermediate layers, in which W and Si are concentrated in the boundaries of graphite particles and a matrix, wherein said graphite-containing heat-resistant cast iron comprises 3.5-5.6% of Si and 1.2-15% of W on a weight basis, and wherein a ratio (Xi/Xm) of a weight ratio Xi of W in said intermediate layers to a weight ratio Xm of W in said matrix is 5 or more and a ratio (Yi/Ym) of a weight ratio Yi of Si in said intermediate layers to a weight ratio Ym of Si in said matrix is 1.5 or more, said heat-resistant cast iron having a composition consisting essentially of, on a weight basis, 1.5-4.5% of C, 3.5-5.6% of Si, 3% or less of Mn, 1.2-15% of W, and 1.0% or less of a graphite-spheroidizing element, the balance being substantially Fe and inevitable impurities, said graphite-spheroidizing element comprising 0.003-0.02% by weight of S and 0.05% or less by weight of a rare earth element in addition to 0.005-0.2% by weight of Mg as a graphite-spheroidizing element, said graphite-containing heat-resistant cast iron having a structure comprising a matrix based on a ferrite phase in an as-cast state and after heat treatment.