OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 5 4 3 a b Fig. 6. Tensile test result of weld fabricated by cylindrical threaded pin profile: a – bar chart of UTS; b – stress-strain diagram Fig. 7. Fractured specimens after tensile test of joints fabricated using taper cylindrical pin a b Fig. 8. Tensile test results of welds fabricated by cylindrical taper pin profile: a – bar chart of UTS; b – stress-strain diagram The results indicate that the tensile strength of welded joints fabricated using threaded cylindrical pin profile and taper cylindrical pin profile is lower, than that of the base material. Based on the results presented, it is evident that with increasing tool rotation speed (RPM), the strength of the welded joint and the joint efficiency increases, regardless of the tool tip profile. For the tool with threaded cylindrical pin profile, joint efficiency and tensile strength are highest at 575 rpm and 60 mm/min and are equal to 84.5 % and 142 MPa, respectively (table 5). Lower values of rotation speed (320 rpm and 45 mm/min) result in slightly lower values of the joint efficiency and tensile strength (138 MPa and 82.6 %).
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