Heat resisting steel and steam turbine rotor shaft

Abstract From the Canadian patent

Disclosed is a heat resisting steel whose metal structure is entirely martensite phase produced by tempering after quenching. The steel comprises by weight, 0.05 to 0.20% C, not more than 0.15% Si not more than 1.5% Mn, not more than 1.0% Ni 8.5 to 13.0% Cr, not more than 3.50% Mo not more than 3.5% W, 0.05 to 0.30% V, 0.01 to 0.20% Nb not more than 5.0% Co, 0.001 to 0.020% boron 0.005 to 0.040% nitrogen, 0.0005 to 0.0050% oxygen and 0.00001 to 0.0002% hydrogen. The steel has preferably not more than 10 of the Cr equivalent. The steel has 10 kgf/mm2 or more of 10,0000 hours creep rupture strength at 650;C.