Prerequisites for developing an advanced welding technology for repair of worn elements of steam-conducting systems

The main disadvantage of standard technologies of welding steam pipelines of thermal power plants is that they can allow the presence of defective structures close to the defective ones in the metal of the seam and in the sections of the HAZ. In this regard, the question arises about the development of a new technology that will provide the appropriate structure and properties that will increase the service life of steam pipelines and get a significant economic effect. Goal. The goal is improvement of the technology of welding pipelines of thermal power plants based on the study of the features of the formation of welded joints operating in Creep conditions. Methodology. The level of wear of the elements of the Steam-conducting path was estimated taking into account the provisions of the regulatory documentation of metallographic analysis, determination of chemical composition and properties, as well as the degree of their deformation. Results. It is revealed that welded joints are characterized by initial structural heterogeneity, which is closely related to long-term strength, ductility and impact strength. For example, at different sections of a welded joint, there is a different intensity of transition of alloying elements and, accordingly, a different type of structural component can be formed. The proposed technology of welding repair of damaged elements of steam pipelines using mechanized welding in CO2+Ar provides for the production of welded joints with a higher level of uniformity of structure, chemical composition and properties. Scientific novelty and practical significance. The welding technology has been improved, which includes developing the modes for performing repair work by mechanized welding in an Ar + CO2 environment of steam pipeline samples with a depth of ≥ 20 mm and a width of ≥ 30 mm, and differs from the known ones by using linear energy welding of 1.2–1.5 MJ/m.

Research on the quality of welded joints of P265GH heatresistant steel pipes at electron beam mechanized welding

This paper analyzes the quality of welded joints of high temperature resistant steel pipe at electron beam welding, knowing that the mechanical properties of these types of steels are influenced by the interaction of different processes specific to physical and mechanical metallurgy. Analyzing the values of the local hardening estimator ΔHV10 calculated between the characteristic areas of welded joints, it is observed that it has a decreasing tendency at thermally de-stressed joints, in all areas of the welded joints, especially in the welded seam.

Mechanized Welding with Metal Cored Wire

Currently, there is a steady upward trend in the consumption of flux-cored wires in the global market of welding consumables. One of the rapidly developing technologies for the manufacture of metal structures is shielded gas arc welding with flux-cored wire with a metal core. According to the technology of use, metal cored wires do not differ from solid wires, and even surpass them in some technological characteristics. Taking into account global trends in the development of mechanized welding and the lack of domestic analogues, LLC TM.VELTEK has developed and mastered the manufacturing of high-performance metal cored wire TMB5-MK for welding in mixtures of 82% Ar + 18% CO2, 90% Ar + 10% CO2. The research aimed to study the features of the process of welding with metal cored wire compared to welding with solid wire. It has been established that metal cored wire provides high stability of arc burning in a wide range of welding modes. When welding at the same conditions in the optimal range, the index of stability of arc burning when using solid wire Sv-08G2S is 3 times lower. At the same time, the TMV5-MK wire provides a reduction in spatter losses, an increase in welding productivity and high mechanical properties of the weld metal. It is shown that the stability of the welding process is significantly affected by the electrodynamic properties of the power source and this factor must be taken into account when evaluating the welding and technological properties of welding wires and developing recommendations for their use.