Optimization of new anti-crevice corrosion special thread structure

LI Chuan-hong1, WU Xiu-bin1, WEI Zhi-yong2, LI Qiang2
（1.Department of Mechanical and Automotive Engineering, Laiwu Vocational and Technical College, Jinan 271199,
China; 2.School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China）

Abstract: Aiming at the poor anti-crevice corrosion ability of special threaded joints widely used in gas wells, the structure of typical special threaded joints was optimized and a new type of threaded joints which can resist crevice corrosion was obtained. Based on the finite element method, the change of sealing performance and connection strength of Atype joint under axial tension was analyzed, and the factors affecting the joint strength and sealing performance were obtained. Through numerical analysis, the parameters of the joint such as shoulder angle, tooth bearing surface angle, transition cone surface and secondary sealing surface size were optimized. The results indicate that the optimal combination of parameters are shoulder angle of 60° and tooth bearing surface angle of 2° and coupling pair seal without transition spherical surface. The performance comparison before and after optimization indicate that the optimized joint structure can improve the crack corrosion resistance of the joint without reducing the joint strength.

Key words: gas well string; special threaded joint; finite element method; optimized design