To provide heat resistant cast steel which has excellent thermal fatigue resistance in addition to heat resistance, and is particularly suitable as a material for parts repeatedly heated to a high temperature of ≥900°C such as the exhaust gas manifold and turbohousing of an automobile engine.
The heat resistant cast steel is an alloy composed of by mass, 0.2 to 1.0% C, 8.0 to 45.0% Ni, 15.0 to 30.0% Cr, ≤10% W and 0.5 to 3.0% Nb; wherein, [C-0.13Nb]: 0.05 to 0.95%, and the balance Fe with inevitable impurities. In the cast structure, MC type carbides are dispersedly present by an amount in the range of 0.5 to 3 atomic %, and M23C6 type carbides by an amount in the range of 0.5 to 10 atomic %, and the matrix phase consists of an austenitic phase essentially consisting of Fe-Ni-Cr. The steel has a mean thermal expansion coefficient of ≤20.0×10-6 in the temperature range from a room temperature to 1,050°C, and has a tensile strength of ≥50 MPa in the temperature range of ≤1,050°C.
HAMANO SHUJI
NODA TOSHIHARU
