COMPARATIVE INVESTIGATIONS INTO NAVAL WELDED STEEL, METALLOGRAPHY AND MICROHARDNESS

The purpose of this paper is to make comparative investigations of heat affected zones (HAZ) at naval welded structures in condition of normal welding (submerged arc welding– NW), ultrasonic welding (ultrasonic submerged arc welding– UW) and after thermal stress-relief (HT) and ultrasonic stress-relief (UT) methods. After welding this steel exhibits an uniform field of hardness, because it is low-alloy steel with a low carbon percent. The alloying elements can produce carbides and nitrides which may cause problems.Post weld heat treatment, such as thermal and ultrasonic stress relief methods reduces the residual stress field and solves the problems with improvement of mechanical characteristics.