The peculiar features of development of structural heterogeneity at high-temperature heating in the unstable fusion zone of the austenitic weld with the pearlite steel were considered. It was shown that one of the factors influencing the high nickel content in the weld and low heat input of welding on reduction of width of ferrite interlayer is the decrease in overheating and degradation of carbides in the HAZ metal. However, these changes do not prevent the film precipitation of carbides and embrittlement of metal between the fusion zone and the HAZ. The alloying of austenitic weld metal with nitrogen, formation of nitride particles being more stable than the carbides, and refining the grains facilitate the increase in stability of structure, inhibition of carbide reactions and more uniform distribution of carbides in the fusion zone with pearlite steel, which improves the properties of welded joints of dissimilar steels. 14 Ref., 7 Figures. K e y w o r d s : arc welding, welded joints of dissimilar steels, fusion zone, structural heterogeneity, diffusion of carbon, austenitic weld, nickel, nitrogen, decarburized zone, carburized zone, heat affected zoneDuring manufacture and repair of petrochemical, oil refining, power and other technological equipment the welded joints of dissimilar austenitic and pearlitic steels are applied, which operate at the high (above 350 °C) temperatures. To the joints of dissimilar steels the joints of heat-resistant alloyed steels with austenitic weld are also referred produced in case when the postweld heat treatment is impossible. The welding of such steels is carried out with the use of austenitic materials with a high (more than 13 %) nickel content. At the same time, the compliance of nickel content in the weld metal with the level of alloying of the pearlite steel and operating temperature is provided. The non-compliance of this condition results in development of structural heterogeneity in the fusion zone of the pearlite steel and the austenitic weld as a result of redistribution in carbon diffusion. Such a fusion zone is considered to be unstable [1].The characteristic features of structural heterogeneity in the unstable fusion zone is the presence of interlayers, i.e. the carburized one with a high hardness in the transition layer of austenitic weld and the ferrite one with a low hardness in the HAZ of pearlite steel. The diffusion of carbon is facilitated by the gradient of its thermodynamic potential between the austenitic weld and the pearlite steel [1][2][3]. In the austenitic weld it has lower values due to the presence of strong carbide-forming elements such as chromium, molybdenum, vanadium, etc. which bind carbon into carbides. In the pearlite steel a higher value of potential is caused by the presence of unstable carbides and free carbon in the solid solution.The transportation of carbon in the unstable fusion zone occurs according to the mechanism of both atomic and reactive diffusion [2]. During the atomic diffusion free carbon in the solid solution of metal is...

Pilot Plant of Welding Equipment is the leading production facility of Science-Technology Complex «E.O. Paton Electric Welding Institute». From the moment of the start of its operation in 1959, the main objective of the Plant was optimization of the technology of manufacturing new welding equipment, developed by scientists of the Electric Welding Institute. Over the past years, the Plant produced a lot of unique equipment-from high-precision small-sized units used for welding in space, up to high-power automated machines of «Styk», «Sever» type, for instance for flash-butt welding of large-diameter pipes, for welding longitudinal welds of pipes under the conditions of automated manufacturing, etc. At present the Plant focuses on manufacturing reliable welding equipment fit for operation under any production conditions. Today manufacturing of special-purpose welding and surfacing equipment, including automatic equipment, by special orders from major users takes up a considerable share of production. PPWE was the first to master batch production of inverter equipment in Ukraine. The Plant has good prospects of economic, and production development, and its products enjoy high consumer demand. Your enterprise has been successfully developing over the recent years. What promoted or contributed to beginning of intensive growth? Strategy of enterprise development was elaborated for long-term perspective. Our goal was to become the leaders in the production of welding equipment in Eastern Europe. To reach this goal, radical reconstruction of the Plant capacities was performed, modern market of welding equipment was analyzed, and priorities in the range of manufactured products were determined. Starting from the moment of its founding up to 1990, the Plant serially produced classical welding equipment (transformers, semi-automatic machines, rectifiers). Over all these years, hundreds of thousands of equipment pieces were manufactured for enterprises from almost all continents of the world. Over the next years, despite the instability of economic situation in the country, the Plant management always invested into enterprise development and brought together a team of professionals, literally «living in their business». This brought its results and today we occupy a significant part of the market of welding equipment and consumables in Ukraine and outside it. Over the last decade, production volumes increased almost

Manufacture of exhaust-heat boiler of steam-gas plant of 150 MW capacity for Alchevsk Iron & Steel Works allowed using the secondary metallurgical gases as alternative to the nature gas. Its modular design, high closeness of arrangement in heat-exchange blocks of thin-walled small-diameter pipes of heating surfaces decreased the dimensions of the plant and increased its efficiency factor up to 44.6 %. Due to a narrow gap between the pipes the butts of these pipes occurred to be hard-to-reach for welding and control. This caused the increase in the amount of inadmissible defects in welds, and also made the welded joints of pipes almost not suitable for the repair. The making of welded joints on different stands by applying methods of argon-arc and combined welding allowed improving the quality, gave an opportunity to perform repair and to realize their X-ray, ultrasonic and visual-optic control. The manufactured heat-exchange blocks withstood the hydraulic test without appearance of leakage in welded joints, were installed and put into service. Significant saving of fuel for industrial enterprises of the metallurgical industry is the application of secondary fuel gases, such as blast furnace, converter, coke gases, forming during the metallurgical processes. Their application as a fuel, alternative to natural gases, was feasible by using steam-gas plants (SGP) of a combination cycle. In these plants the gases are mixed to form the safe concentration and required heat-generating ability and are burnt out, and the generated heat is converted into mechanical and electric energy. At Alchevsk Iron & Steel Works (AMK) a complex of SGP of total power of 300 MW (two blocks of 150 MW) was manufactured. The designing of SGP was made by the Mitsubishi Heavy Industries Company (Japan) with participation of Industrial Union of Donbass [1]. Construction of steam-gas electric plant for utilization of blast furnace, converter and coke gases (similar to AMK) was planning at F.E. Dzerzhinsky Dneprovsky Iron & Steel Works. The Iron & Steel Works «Azovstal» also announced about implementation of two SGP [2]. At AMK the operation of two steam-gas blocks allows providing the almost full need in electric power, keeping the standards for harmful gas blow-outs, accepted in EU.One of the SGP main components is an exhaust-heat boiler, which was designed from heatexchange modules of the evaporator, steam superheater and economizer.The heat-exchange modules were assembled of header panels, each of them has inlet and outlet headers (Figure 1, a, b) with three rows of A, B and C holes on the lateral surface, in total 40 pcs in each one (Figure 2, a). Concentrically to these holes the connecting pipes are welded-on by fillet weld, which in turn are joined by butt weld to pipes of heating surfaces (Figure 2, b). The fillet joints of connecting pipes and butt joints of pipes of heating surfaces were made with a full penetration. Connecting pipes in the middle and edge row were bent at 25 and 50° angle, respectively. Diameter of pipes and connecti...

Mechanized multilayer MIG/MAG welding by high-alloy wires is associated with the feasibility of formation of lacks of fusion and slag pieces in weld metal. Therefore, the improvement of technology, in particular the selection of shielding gas composition, is urgent. Feasibility of application of mixtures CO2 + 3 % N2 and CO2 + 3 % N2 + 0.5 % O2 as a shielding gas in mechanized arc welding of dissimilar steels is shown. It is shown that the metal oxidation occurs mainly in the inter-dendrite regions, intensity of which is increased with increase in amount of nickel in the welding wire. Weld metal alloying with nitrogen does not change the intensity of metal oxidation process and almost has no influence on slag crust removal from the deposited metal surface. 17 Ref., 2 Tables, 3 Figures.

No abstract