Comparison of ST52/E355 and 45# Steel in Weldability, Mechanical Properties and Application Scope:
| grade | ST52/E355 (with heat treatment) | CK45 (with quenched & tempered) |
| Tensile | above 600 MPa | above 700 MPa |
| Yield | above 500 MPa | above 550 MPa |
| Elongationδ5 | ≥15% | ≥15% |
| Hardness | HB 180-210 | HB 220–280（HRC 22–30） |
| Weldability | Excellent weldability, direct welding available, no complicated preheating required | Poor weldability; high carbon content, easy to crack during welding, strict preheating and post-heating required |
| Machinability | good,easy to machine | good hardness after QT,good machinability |
| Impact | Good low temparature toughness | |
| advantage | Sufficient strength, good toughness, excellent weldability | excellent comprehensive mechanical properties, high strength, good wear resistance, good fatigue resistance |
| Applications | Steel structures, frames, pressure vessels, pipelines, bridges, frames, welded parts | Shafts, gears, piston rods, bolts, crankshafts, wear-resistant parts, key stressed parts |
| Notes: stress stabilizing treatment only can reduce the residual stress and deformation |
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