No. 45 Steel Chemical composition mass fraction% | C: 0.42 ~ 0.50 Chemical composition mass fraction% | Si: 0.17 ~ 0.37 Chemical composition mass fraction% | Mn: 0.50 ~ 0.80 Chemical composition mass fraction% | Cr≤: 0.25 Chemical composition mass fraction% | Ni≤: 0.30 Chemical composition mass fraction% | Cu≤: 0.25 Recommended heat / ℃ | normalizing: 850 Recommended heat / ℃ | Hardening: 840 Recommended heat / ℃ | Tempering: 600 Mechanical properties | σb / MPa≥: 600 Mechanical properties | σs / MPa≥: 355 Mechanical properties | δ5 (%) ≥: 16 Mechanical properties | ψ (%) ≥: 40 Mechanical properties | AKU / J≥: 39 Delivery status hardness of steel HBS10 / 3000, ≤ | No heat treatment of steel: 229 Delivery status hardness of steel HBS10 / 3000, ≤ | annealed steel: 197 |