Fasteners, bearings, gears, springs, moulds and dies are the basic parts of machinery manufacturing, which directly affect the quality and reliability of machinery. Iron and steel materials are the material basis for the manufacture of basic parts, at present, the annual output of steel for basic parts in China is about 24 million tonnes, which is a large amount of wide range of special steel products. Fasteners, bearings, gears, springs, moulds and other service environment is different, the quality of the material requirements are also different. It can be said that the quality of steel used in basic parts determines the level of machinery manufacturing, but also represents the overall development of special steel features and level.
Fasteners are known as the 'rice of industry', is the largest application of basic parts. 2023, China's fasteners with steel amounted to 12.5 million tonnes. Steel for fasteners covers almost all steel categories, mainly including cold heading steel, alloy structural steel, stainless steel, heat-resistant steel, etc., the standard strength level in the range of 400 MPa ~ 1200 MPa. Fasteners are usually manufactured using the cold heading process, which requires the steel to have good cold heading properties. Depending on the application scenario, steel for fasteners also needs to be resistant to fatigue damage, delayed fracture, corrosion, high and low temperatures.
Low-cost competition for fasteners has prompted MnB steel to replace CrMo steel in large quantities. At present, China's standard (GB/T 3098.1-2010) in the fasteners of the highest grade 12.9, mechanical lightweight requirements of 14.9 and above high-strength fasteners, in addition to the production process issues need to be resolved, but also to focus on delayed fracture and fatigue damage and other issues.
