Development of High Strength Bolts

With the development trend of energy, vehicles, mechanical equipment, engineering construction, light industry and other fields, there are better regulations for the application materials and bolt manufacturers of various tightening bolts, and there is an urgent demand for high-toughness bolt raw materials. ． In the past 10 years, countries all over the world have attached great importance to the development of this technology. In my country's key basic research and development project (973) "Major Basic Research of New Generation Steel Materials" has been launched, and the research and development of high-strength bolt steel Design is one of the key research topics. The development trend of high-strength bolts is summarized as follows: 1) High-toughness and high-performance stainless steel plates. With the increase of the compressive strength of steel, the sensitivity to delayed time fracture increases. in compressive strength>When the compressive strength level is 900MPa and the strength is ≥31HRC, the sensitivity to delayed time fracture gradually expands. The greater the stress of the bolts in active service, the greater the damage after fracture. Therefore, the development and design of high-strength bolt steels with high-quality anti-delay time fracture performance will ensure the safety of people's lives and funds, and expand the main purpose of high-strength bolts. Positive. 2) Control costs and reduce energy consumption. Use cheap boron steel to replace carbon steel containing Ni, Cr, Mo and other high-value lines to control costs; use cold forging instead of hot forging to reduce the heat treatment process of non-heat-treated steel, which does not need to be softened before forging The widespread application of low-carbon environmentally friendly non-quenchable steel and high-precision rolled plates that do not require peeling and drawing can not only reduce energy consumption, but also alleviate the carburization tendency of external thread cusps and increase the yield of bolts. 3) Improve the product quality and stability of bolt steel. The stability and service life of bolt parts are closely related to the smelting quality and surface condition of bolt steel, and even some processing properties are not so much related. According to improving the purity of stainless steel, reducing S and P components can improve the deformation ability of steel, alleviate dislocation aging, reduce non-metallic material impurities in steel, improve the ductile and plastic deformation of stainless steel, and improve the delayed time fracture resistance of stainless steel. ． In addition, the production precision, tightening technology and inspection methods of finished bolts are also the main factors affecting the stability of high-strength bolts.