X1CrNiSi18-15-4 or 1.4361
C: 0.015% max Si: 3.70%-4.50% Mn: 2.00% max P: 0.025% max S: 0.010% max Cr: 16.5%-18.5% Mo: 0.20% max Ni: 14.0%-16.0% N: 0.11% max