Faiza B., Sonia D., Rafik H., Ali B.

The aim of our study is the use of ultrasound to show experimentally the change of the mechanical behaviour of a material initially homogeneous and isotrop after a welding operation. In fact, the heterogeneous and anisotropy nature of welds leads to diffusion, attenuation, deviation and division phenomena of the ultrasound beam. The extent of this phenomena is closely connected to the metallurgical structure obtained after welding and which depend on the welding parameters (energy and velocity) and the welding process (type, position...). The pursuit of this objective (to make the connection between homogneity, isotropy and the ultrasound beam) lead us to develop and realise an immersion ultrasound test bench based on a normal incidence of an ultrasonic pulse transmission trough the material to be characterised. All this device is automated and computer controlled. The cartography of an ultrasound beam generated in immersion by a 2.25 MHZ fixed piezoelectric transducer, operating on impulse after crossing the base metal and the joints of a carbon steel welds realised by flux wire and submerged arc process are obtained after an automatic scanning of the opposed surface to the beam with a transducer of the same frequency fixed on conical sole made such as the contact surface should be a 2mm diameter disc. The perturbations undergone by the ultrasound beam in the base metal and in the joint change in a significant way, and conclusions are made. The macrography and the micrography analyse as well as observations made on the perpendicular and parallel plans of the welds give informations about the grains slope and growth. The experimental results validation are possible and the reliability of the method is confirmed and is able on the physical metallurgy point of view to be a hudge information source.