OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 Table 2 shows the modes for joints steel 45 + R6M5 and steel 45 + steel 45, obtained by friction. Ta b l e 1 Modes of resistance welding of blank pairs (steel 45 + steel 45) and (steel 45 + steel R6M5) Mode No. Total draft, mm Secondary voltage, V Heating time, sec 1 2 3.5 15–25 2 3 3.5 15–25 3 4 3.5 15–25 4 5 3.5 15–25 5 6 3.5 15–25 6 10 3.5 15–25 Ta b l e 2 Modes of friction welding of blank pairs (steel 45 + steel R6M5) and (steel 45 + steel 45) Mode No. Rotation speed, rpm Specific heating pressure, N/mm2 Specific forging pressure, N/mm2 Heating time sec 1 1,500 156 236 2 2 1,500 156 236 8 3 1,500 156 236 9 4 1,500 156 236 12 5 1,500 156 236 15 6 1,500 156 236 25 7 1,500 156 236 30 8 1,500 27 27 3 9 1,500 27 27 5 10 1,500 60 60 5 11 1,500 60 60 10 12 1,500 100 100 6 13 1,500 160 160 5 14 1,500 170 170 10 All blanks and the ones from a solid bar of steel 45 and steel R6M5 were annealed at 850 °C for 10 hours after welding. The specimens were turned on a lathe to ensure the uniformity of dimensions in diameter. The specimen diameter at the welding point was 17.2 ± 0.05 mm, and the specimen length was 170 mm. The grip sections of the specimens were cut off without further machining. As it was mentioned in the introduction, internal friction was determined by the static hysteresis loop method. This fact allows determining the energy dissipation almost directly in the weld [1, 3–15]. The research was conducted on a KM-50-1 testing machine designed for torsion testing of metal specimens. The energy dissipation measurement by the static hysteresis loop method was conducted when loading the welded joint with an alternating torque, and the displacements were recorded by a laser sensor with digital indexing LAH-G, with a resolution of 0.5 μm. The indicator readings were taken after several preloading cycles, which corresponded to the closing of the hysteresis loop. After the loop was removed at one amplitude of the alternating torque, the loading cycle was performed at larger torque amplitude, for which a hysteresis loop was also built and so on. The welded joint loading with torque was carried out only in the elastic deforming area of the entire specimen. The energy dissipation in the welding area when applying an alternating moment greater than the static
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