Applied research of high-strength steel utilization for a track of demining machine in terms of mechanical properties

Abstract

AbstractThe aim of this paper is to investigate welded joints of high-strength steel S960 QL manufactured by using three different welding technologies, namely the electron beam, the laser beam, and the metal active gas (MAG) technologies. The experimental part included tensile strength evaluation, microstructural analysis of welded joints, and hardness measurement. Welded joints (WJ) have consisted of the identical steels and the identical thickness (10 mm). Destructive tests confirmed that welded joints are characterized by the tensile strength similar to the base material. Upon further observation, we can conclude that microhardness was characterized by the lowest value in the softening zone (SZ) and the highest value in the hardening zone (HZ). The degree of softening was 11% for the electron welding, 13% for the laser welding, and up to 27% for the conventional MAG welding. This also corresponds with the size of the SZ, which was the widest in welds made with the MAG technology. The laser beam weld produced up to 50% lower heat-affected zone (HAZ) compared to the conventional MAG technology. In case of the electron beam, this number is even higher. On the contrary, highest hardness was observed for the electron beam technology, where the hardness in the hardening zone increased by up to 40% when compared with the base material. Tests show the possibility of production of reliable welded joints, which meet the complex requirements for lifetime and quality (according to the standard EN 6520–1 focusing on defects categorization and EN 5817 dealing with defects tolerance).