Development of EN S460NL High-toughness Structure-purpose Pipe

The EN S460NL steel pipe is development by means of adding chemical elements like Cr，Mo，Cu，Ni and V，etc.into the 20Mn steel，and the pipe normalization heat treatment process.Microstructure and mechanical properties of the said pipe are tested.The test results reveal the facts as below.The metallographic structure of the pipes is of pearlite+ferrite matrix with dispersion-distributed fine carbides.And during the tensile testing process，the said fine carbides are dislocated and piled up，which leads to the development of dislocation tangling and network structure inside the ferrite matrix.The impact fracture has the typical tough dimple characteristics.All these microstructure characteristics enable the S460NL steel pipe to possess not only high strength，but also excellent low-temperature impact toughness，i.e.，yield strength>500 MPa，tensile strength：640-680 MPa，elongation rate≥22%，and impact energy at-50℃>100 J，and thus to have met the customer-specified requirements.