Harm caused by unqualified high-strength galvanized bolts

Bolt connection is a kind of tightening mechanical parts, generally including bolts, screws and sealing rings (hereinafter referred to as bolts). It is used universally. It can be found in various machinery and equipment, vehicles, road bridges, structures and other places. It has a variety of specifications and models, and different types of performance and main uses. For example, high-strength bolts with phosphated surfaces are used in steel frame structures, and heat-resistant bolts are used in steam turbine marine engines. High-strength galvanized bolts produced by the surface hot-dip galvanized process are used as components for connecting power line towers and substation structures because of their excellent outdoor corrosion resistance. So far, no other bolt has been able to take his place. The hot-dip galvanizing process of high-strength galvanized bolts will also result in rough surfaces and uneven thickness. This will also lead to a very large dispersion of its torque coefficient. The exploration of the distribution characteristics of the torque coefficient of hot-dip galvanized bolts is rarely mentioned in technical standards and materials, which adds inconvenience and randomness to daily engineering construction. Bolts that are too tight or too tight during the installation process may cause hidden safety hazards. With the increase of the rated voltage of China's power grid, higher requirements are placed on the safety and stability of power line towers and distribution substation structures. Due to insufficient research on basic data such as torque coefficients, the application of large and medium-sized high-strength galvanized bolts has been hindered. For example, the hot-dip galvanized bolts in the poles and towers can only be partly loosened after several years of operation of China's UHV transmission lines. This requires a lot of manpower to retighten the bolts to eliminate the unsafe protection factors caused by the loosening of the bolts. Therefore, the increasing standardization of high-strength galvanized bolts also brings convenience to everyone's power lines, and also reduces the burden on the working voltage field of the power grid.