Laser and mechanical cutting effects on the cut-edge properties of steel S355N

The execution of steel structures was recently regulated by the standard EN 1090 that introduced both the concept of execution class and minimum requirements for elements processed by cutting techniques such oxy-fuel, plasma and laser cutting. The last technique is especially appealing for structural details characterized by complex geometries and high precision machining. With these premises, this work compares several properties of S355N steel plates machined by traditional mechanical versus laser cutting, in view of the limitations provided by EN 1090 on local hardness HV10 of straight cutting surfaces and high-cycle fatigue applications. In particular, the microstructural characterization included optical and electron microscopy, microhardness, hardness and residual stress analysis on cut edges of 5 and 15 mm S355N steel plates. Moreover, the high-cycle fatigue behaviour was studied both in base material coupons and elemental bolted connections. Whilst the mill and drill cutting entailed straight and round cut edges with superior properties, material and high-cycle fatigue properties of edges obtained by laser cutting satisfied both EN1090 requirements and the Eurocode 3 FAT classes.