Microstructural and fracture analysis of microalloyed steel weld metal

Abstract In this paper is presented behavior of microalloyed steel weld metal with niobium during impact testing, as well as microstructural characterization. Impact tests were done on instrumented Charpy pendulum at room temperature, at -40 0 C and -55 0 C. At room temperature, crack propagation energy is much higher than crack initiation energy, while at -40 0 C and -55 0 C crack growth energy is lower than crack initiation energy. Fractographic investigation of the fracture surfaces has shown that at room temperature ductile trans-granular fracture is dominant, with a small amount of brittle trans-granular fracture. At lower temperature, the share of brittle fracture is increased, and inter-granular brittle fracture becomes dominant.