ACOUSTELASTIC EVALUATION OF WELDING AND HEAT TREATMENT STRESS RELIEVING OF PRESSURE VESSEL STEEL FOR ANGRA III

摘要

Currently the knowledge of non-destructive techniques allows to evaluate the stresses on components and mechanical structures, aiming at physical security, preservation of the environment and avoid financial losses associated with the construction and operation of industrial plants. The search for new techniques, especially applied in the nuclear industry to assess status more accurately, voltage safety and to ensure structural integrity, for example, core components of the primary circuit, such as the reactor pressure vessel and steam generator has become of great importance within the community of non-destructive testing. This paper aims to contribute to the non-destructive technique development in order to ensure the structural integrity of nuclear components. One acoustelastic evaluation of steel 20 MnMoNi 55, used in pressure vessels of nuclear power plants were performed. The acoustic birefringence technique was use to evaluate the acoustelastic behavior of the test material in the as received condition, after welding and after the stress relief heat treatment. The constant acoustelastic material was obtained by an uniaxial loading test. It was found a slight anisotropy in the material as received. After welding, a marked variation of acoustic birefringence in the region near the weld bead was observed. The heat treatment indicated a new change of acoustic birefringence. Obtaining the acoustelastic constant allowed the evaluation of stress in the different conditions of the weld and treated material.