Joachim E. Hoffmann, Mario D. Elicker, Helmut Clemens, Johann Lambert, Christoph Behr, Heinz Ney
May 28, 2013
The influence on the Charpy V-notch impact behaviour in the transition region is investigated taking into consideration the residual stresses, work hardening and the surface topology at the notch root caused by manufacturing. Three materials were made available for the investigation, an unalloyed structural steel in the normalised and in the partially austenitised microstructural state, a water quenched hardened and tempered high strength, fine grained structural steel, and a heat treated steel. Initially, the effects of the major geometric parameters are identified with constant manufacturing conditions at the notch root (part I). As shown in the present contribution, the required almost constant notch root manufacturing conditions are obtained by means of a defined notch grinding process. Following notch machining of two steels, a stress relieving heat treatment was carried out. This heat treatment relieves virtually all the macroscopic residual stresses and the work hardening in the surface layer. For constant notch manufacturing conditions, the notch root radius is the most effective geometrically influencing factor at low temperature. The specimen width has the least influence. Increasing level of notch impact energy reduce the effect of the geometric parameters. This is the case for increasing test temperature just as for tougher material states following partial austenitising of the unalloyed structural steel as well as for the heat treated steel with the finest microstructure. The present results provide a solid basis for further investigations (part II) which are to detect specifically varied notch manufacturing conditions on the Charpy V-notch impact behaviour.