Keyword: «welding»

The paper proposes a technology for welding a saddle branch to polyethylene pipes, which allows to extend the range of permissible ambient temperatures for welding to minus 45 ° C. Shown are the results of separation tests of welded joints obtained at low temperatures. The use of the developed welding technology ensures the formation of a material structure in a welded joint, similar to the structure of the material of a welded joint obtained under conditions of permissible temperatures.

The features of the stress state, physical-mechanical and structural properties of welded joints of structural steels 09G2S and St3sp, made at low climatic temperatures, are studied. Welded samples were obtained by manual arc welding using domestic electrodes UONI-13/MOROZ, HOBEKS-K-54, LB 52TRU. During the research, pulsed arc welding was tested in comparison with the traditional method of direct current welding. When welding in the cold, an increase in the level of tensile residual welding stresses by an average of 40 ... 50% is observed compared with welding at room temperature. Features of the structure and mechanical properties during welding at negative temperatures are revealed.

The development of the theory and technology of high-entropy alloys (HEA), consisting of several basic elements, poses a number of urgent tasks for researchers to comprehensively study the properties of new materials that determine the areas of their practical application. This report presents an overview of scientific publications devoted to the study of the mechanical properties of the most studied HEAs based on the CoCrFeNiMn transition metal system, as well as to the study of the influence of certain types of welding on the quality indicators of welded joints. As a result of the work performed, it was found that the strength and plastic properties of the considered HEAs correspond to the best samples of high-alloy austenitic steels used for cryogenic technology, and have the prospect of further improvement.

Examples of destruction of welded joints of sections of main gas pipelines in Yakutia under the influence of fields of residual welding stresses are considered. The results of experimental studies of residual stress fields of welded joints of plates made by arc welding under conditions of low climatic ambient temperatures are discussed. The mechanism of the influence of residual stresses on the occurrence of additional plastic deformations in the zones of welded joints after welding under conditions of low climatic temperatures is presented.

In this paper, a study of structural transformations of 14G2SAF pipe steel during welding, changes in its strength and ductility characteristics when simulating real thermal cycles under different ambient temperature conditions is carried out. The most optimal intervals of cooling rates were selected experimentally.