Research on the behaviour and mechanism of void welding based on multiple scales

Abstract As the core foundation of major national equipment, large forgings have a great influence on the national economic construction, the development of national defence equipment and the development of modern cutting-edge science and technology. In the production of large forgings, welding the internal void of forgings is a technical problem that directly affects the quality of large forgings. In view of the phenomenon of void welding in large forgings, the behaviour and mechanism of void welding were deeply studied based on the stretching test and molecular dynamics simulation, combined with a lot of theoretical analysis. The results show that multi-pass stretching deformation is a kind of plastic deformation process which can eliminate void defects. When the forging ratio reaches 2.2, the void can be welded completely and the tensile strength can be restored to the level of the matrix. With the increase of compression deformation, the stress will increase sharply, especially at the grain boundary. In addition, the main void welding mechanism of 30Cr2Ni4MoV steel is the recrystallization and grain growth mechanism. Recrystallization and grain growth are of great significance for promoting the reduction of void volume and realizing metallurgical bonding of the interface.