Fracture performance testing and modeling of butt weld metal

•The size of the plastic zone was recorded by a digital microscope. The average value of the plastic zone along the crack tip was estimated quantitatively.•The yield strength and fracture toughness obtained from the specification-compliant tensile and Charpy impact tests demonstrated the results of the boundary effect model, which implies that the boundary effect model is a feasible approach for predicting the material properties of weld metals.•The elastoplastic fracture mechanism for the weld metal derived from the boundary effect model is consistent with the SEM analysis results.•The fracture toughness of Q235 butt weld metal is higher than that of the base material and is not susceptible to fracture.