Abstract:
As a critical manufacturing process for threaded connections, thread rolling directly determines the forming quality and reliability of threads, and further affects the service stability of complete equipment. To establish a stable thread rolling process, MJ5-specification GH2132 bolts were taken as the research object. By constructing a high-precision thread rolling simulation model, the effects of different rolling parameters on the residual stress at the thread root region are investigated, and the variations of thread morphology and surface microhardness are also explored. Furthermore, low-temperature tensile fatigue tests (0 ℃ and −50 ℃) of threaded specimens are carried out. The research indicate that with the extension of rolling holding time, the residual compressive stress and surface hardened layer increase firstly and thenlevel off, while the thread surface morphology is improved initially but later exhibits scratch and cracking damage. The fatigue life at both 0 ℃ and −50 ℃ increases first and then stabilizes, and the fatigue life at −50 ℃ is higher due to the low-temperature strengthening effect. The rolling parameters of Group 2 achieve full thread forming, optimal matching of compressive stress and hardness, and the best fatigue life. The results can provide a basis for process optimization of GH2132 bolt thread rolling and improvement of low-temperature service reliability.