Gr65 (equivalent to Q450) high-strength steel produced by Shanghai Baosteel is also used in the design of transmission line steel pipe poles in my country, but there is no experience in using it in steel pipe tower structures. This study mainly explores the feasibility of applying high-strength steel pipes in transmission line structures through the study of several key issues in the design of Q460 high-strength steel pipe towers.

1. Research and test on welding process evaluation of Q460 high-strength steel. Welding process evaluation of Q460 high-strength steel is a key process for processing steel pipe structures. The test results show that: Through complete welding process program guidance and effective inspection and control, the welding quality of Q460 steel can meet the welding quality requirements of steel pipe towers and ensure the safety and reliability of steel pipe towers. The "Welding Process Assessment Report" formed based on the test results can be used as a steel tower processing welding process guidance document.
2. Research and connection test on the cross-diagonal "cross" plug-in joints. Through tests, this project has thoroughly improved and optimized the connection force mechanism and detailed structure of the cross-diagonal "cross" plug-in joints. The results prove that both in terms of strength and stability, the cross-diagonal "cross" plug-in joints can meet the structural safety requirements.
3. Research and testing of forged high-neck flanges. The forged high-neck flanges designed in this project are mainly used for the connection of main materials. The rigidity theoretical calculation is adopted and the setting of high necks is used to effectively control the welding of steel pipes and flanges. The influence of welding stress on the flange plate. The comparison between test results and finite element analysis shows that the design method of forged high-neck flange adopted in the design is practical and feasible. The strength of forged high-neck flange meets the specification requirements, is safe and reliable, and can meet the engineering application requirements.
4. Through the true tower test of the Q460 high-strength steel tube tower, the rationality of the structural layout of the tower and the reliability of the node structure were comprehensively verified. It was also a test of forged flanges, Q460 steel welded connections and cross-diagonal materials. The successful completion of this test brought a successful conclusion to the test work of this project.
   This project has obtained first-hand information on the design of high-strength towers through research on the above aspects, providing fresh experience for promoting the use of Q460 steel in transmission tower design. As the supporting project of this project, 500kV Liantang Substation~Q460 high-strength steel is used throughout the Sijing Substation Line Project, giving full play to the characteristics of large radius of gyration of steel pipe section, high steel strength and large bearing capacity, effectively saving investment.