Controlling the Parameters of the Metal Crystal Lattice of the Welded Joints Made Underwater
S. Yu. Maksimov, O. O. Prilipko, O. M. Berdnikova, T. O. Alekseienko, Ye. V. Polovetskiy, Yu. A. Shepelyuk
E. O. Paton Electric Welding Institute, NAS of Ukraine, 11 Kazymyr Malevych Str., UA-03150 Kyiv, Ukraine
Received: 27.08.2020; final version - 11.12.2020. Download: PDF
The quality enhancement of welded joints, the development and improvement of electric arc processes and devices require complex experimental and theoretical research. One of the most promising methods, that provide the necessary strength and ductility of the joint metal, is the method of welding in an external electromagnetic field. The stirring of the weld pool has a significant effect on the process of molten metal crystallization, gas exchange reactions, and formation of the weld metal structure. The conducted studies confirm the effectiveness of using external electromagnetic action in underwater welding conditions to improve the mechanical properties of the weld metal. To a further improvement of the technology of mechanized underwater welding, mathematical modelling methods are used, as the most rational method for optimizing experimental studies in an aqueous environment. Mathematical models made it possible to take into account the influence of both the primary factors, namely, the specified current and voltage in the welding circuit and inductor, the properties of materials and the conditions of the process, and secondary ones—the formation of the structure of the weld metal and heat-affected zone, on the properties of the welded joint. The developed algorithm makes it possible to simplify the calculations to optimize the technological process and improve the quality of the welded workpiece. Using the developed program in the Delphi 7 language, numerical experiments are carried out to study the behaviour of liquid metal in the weld pool depending on the parameters of the external electromagnetic effect and welding modes. Metallographic studies of the welded joints metal, which made according to the standard technology and in the optimal modes of external electromagnetic influence, showed that in the welded joint metal overheating area, obtained without external electromagnetic influence, the most significant gradients are observed for the sizes of the lath structures of the upper bainite and for the density of dislocations. This will lead to an inhomogeneous distribution of the level of mechanical properties of the metal, an increase in the level of local internal stresses and, accordingly, to a decrease in metal crack resistance. In the metal of the overheating section of the welded joint, obtained with the use of an external electromagnetic effect, the structure is dispersed with a general decrease and uniform (gradient-free) distribution of dislocation density in the volume of the structural components of the upper and lower bainite, which ensures the strength and crack resistance of the metal. The conducted studies have confirmed the effectiveness of the use of external electromagnetic influence in underwater welding conditions.
Key words: low-alloyed steel, underwater welding, external electromagnetic effect, welded joints, heat-affected zone, dislocation structure, density of dislocations.
PACS: 61.72.Ff, 61.72.Lk, 61.72.Mm, 64.70.dg, 81.20.Vj, 81.40.Wx
Citation: S. Yu. Maksimov, O. O. Prilipko, O. M. Berdnikova, T. O. Alekseienko, Ye. V. Polovetskiy, and Yu. A. Shepelyuk, Controlling the Parameters of the Metal Crystal Lattice of the Welded Joints Made Underwater, Metallofiz. Noveishie Tekhnol., 43, No. 5: 713—723 (2021) (in Ukrainian)