“…Co. Ltd., Hanzhong, Shaanxi, China) continuous-drive rotary friction-welding machine (maximum of 45 kW and 320 kN forging load). According to our preliminary experiments and the literature on 304SS RFW [5,6,9,14], the welding experiments were conducted using welding parameters in which the welding pressure varied from 40 MPa to 200 MPa, rotational speed varied from 500 rpm to 2300 rpm, and welding time varied from 4 s to 20 s, all while under forging pressures of 100 MPa, 120 MPa, 140 MPa, 160 MPa, 180 MPa, and 200 MPa, respectively. During the RFW process, the welding power was recorded by a computer through an A/D converter with a sampling time of 0.01 s, and the surface temperature of the joint was measured by an infrared thermal imaging instrument (Tec VarioCAM@hr, head-HS Infra, Dresden, Germany) with a sampling time of 0.02 s. The data collected by the infrared thermography instrument had been calibrated using the data that thermocouple collected, and the emissivity of 304SS was determined to 0.8.…”