15CRMNMO Executive Standard: GB / T3077-1999 15CRMNMO is an alloy structural steel grades. Unified Digital Code: A34202. Chemical composition of the mass fraction (%): Carbon C: 0.17 ~ 0.23 Si Si: 0.17 ~ 0.37 Mn Mn: 0.90 ~ 1.20 Sulfur S: to allow the residual phosphorus content ≤0.035 P: ≤0.035 allow the residual content of chromium Cr: 1.10 ~ 1.40 Ni-Ni : ≤0.030 allow the residual content Copper Cu: to allow the residual content of ≤0.030 Mo Mo: 0.20 ~ 0.30