Microstructurals transformations on quenched and tempered ASA CA 80 steel welds

Quenched and tempered steels can combine high yield and tensile strengths with good notch toughness, ductility and weldability. These steels are particularly convenient whenever the increase of mechanical resistance gives rise to a proportional reduction of weight. As well known, toughness and soundness of these steels can be affected by welding operations, which induce metallurgical modifications, embrittlement and cracks in the Heat Affected Zone (HAZ). In this paper, an investigation is done on welds of steel ASA CA 80 in the quenched and tempered condition. Bead-on-welds by manual arc welding process were deposited on trial plates, 10 mm thick. Experimental work included metallographic examination and microhardness test survey. The results show the formation of a mixed bainitic-martensitic structures in the HAZ, due the relatively high cooling rate of the re-austenitized region close to the melted zone. Even if toughness can undergo a reduction in the HAZ, the weldability and mechanical properties can be considered satisfactory.