Ultrasonic and metallographic studies of the zone of thermal influence of a carbon steel welded joint in plastic deformation and fatigue

Using metallographic and ultrasonic pulse-echo methods, studies of the destruction process of St3sp steel under uniaxial tension and fatigue were carried out. Samples were cut from the welded joint, namely from the zone of the base metal and the area of incomplete recrystallization in the heat-affected zone. A comparative analysis of the evolution of rough slip bands in the heat-affected zone and in the base metal was carried out. A connection has been established between the Poisson's ratio, determined by the ultrasonic method, and the mechanical characteristics of the material. Methods have been proposed for estimating the plasticity life under uniaxial tension and the number of cycles before failure due to fatigue.