C: 0.040%-0.10% Si: 0.30%-0.60% Mn: 1.50% max P: 0.045% max S: 0.030% max Cr: 15.5%-17.5% Mo: 1.60%-2.00% Ni: 15.5%-17.5% Nb+Ta: 10XC-1.20% B: 0.05%-0.10%