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This study investigates the influence of friction pressure at a given  burn-off length on the microhardness, tensile properties and microstructure of the welded joints from steel 32-2-Mn and 40-Cr-Ni. Phase transformations occurring in the materials to be welded as a result of thermal deformation effects are analyzed. The change in the length of the thermomechanical affected zone (TMAZ) depending on the friction pressure is shown. The results of the distribution of microhardness in the weld, clearly illustrating the formation of hardened and weakened areas. The results of tensile tests of welded joints are given. Analyzed the place of fracture at various welding parameters. The necessity of studying the distribution of internal residual stresses to explain the mechanism of fracture of welded joints is shown.

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This paper presents studies of welded joints of steels 30KhGSA and 40KhMFA made by rotary friction welding. The influence of the forging force on the microstructure and tensile properties of standard specimens and specimens with a notch in the contact zone is analyzed. The results of measuring the microhardness and fractogram of the fracture surface are presented. It has been established that in the selected range of forging forces, the strength of the contact zone is higher than other sections of the thermomechanical affected zone and the base metal of the materials to be welded. In this case, the maximum strength of the contact zone occurs at lower values ​​of the forging force due to the formation of common grains along the contact line as a result of the process of mutual volumetric recrystallization.