Evaluation of high cycle fatigue behavior of flux cored arc welded naval grade DMR249 A grade steel joints for ship hull structures

DMR 249A is a micro-alloyed high strength low alloy (HSLA) steel particularly designed for shipbuilding structures due to its excellent strength-to-weight ratio. In this investigation, the rotating-beam fatigue test was performed on the flux-cored arc welded (FCAW) butt joints of DMR 249A steel. And the fatigue test results compared to mechanical properties and microstructural characteristics. The transverse tensile, microhardness, impact, and fatigue properties were evaluated from across the butt weld. The S-N curve was constructed from the experimental data for the stress ratio R =-1. The evaluated fatigue life of the FCAW joint and parent metal was 366 MPa and 394 MPa, respectively. The maximum achieved transverse tensile strength and impact energy absorption of the FCAW joint was 578 MPa & 174 J. The weld region contains an acicular ferrite microstructure, which exhibited improved properties of strength, toughness, and fatigue crack resistance. From the results, the fatigue strength of FCAW is 92.8% that of the parent metal and 62.8% equal to the tensile strength of the FCAW joint.

Automated summary

The rotating-beam fatigue test was conducted on the flux-cored arc welded butt joints of DMR 249A steel, and the evaluated fatigue life of the FCAW joint was 366 MPa, higher than that of the parent metal (394 MPa). The weld region exhibited an acicular ferrite microstructure, showing improved properties of strength, toughness, and fatigue crack resistance.