National standard for high strength bolts
According to Chinese national standards, the standard for high-strength bolts is GB/T 3632-2018 "Bolts, Screws, Studs and Nuts for High-Strength Fasteners". This standard specifies the classification, size, material, mechanical properties, surface treatment and other requirements for high-strength bolts.
According to this standard, high-strength bolts are divided into two grades: 10.9 and 12.9. Among them, the tensile strength of grade 10.9 bolts is 1000MPa and the yield strength is 900MPa; the tensile strength of grade 12.9 bolts is 1200MPa and the yield strength is 1080MPa. These grades of high-strength bolts are mainly used in engineering structures that have higher connection requirements and bear larger loads, such as bridges, high-rise buildings, automobile manufacturing and other fields.
In addition, the standard also specifies the size range, material requirements and mechanical performance requirements of high-strength bolts. The size of the bolt includes thread diameter, thread length, bolt length, etc. Choose the appropriate size according to the specific use requirements. The material of high-strength bolts is usually alloy steel to ensure its strength and corrosion resistance. In terms of mechanical properties, standards require high-strength bolts to have certain performance indicators in terms of tensile, yield and elongation.
The design, manufacture and use of high-strength bolts in compliance with national standards can ensure the reliability and safety of bolt connections. In engineering practice, high-strength bolts that meet the requirements should be selected and used according to specific engineering requirements and standard specifications to ensure the stability and safety of the engineering structure.
In addition to the national standard GB/T 3632-2018, "Bolts, Screws, Studs and Nuts for High-Strength Fasteners", there are also some common international standards and specifications, such as ISO (International Organization for Standardization) and ASTM (U.S. Society for Materials and Testing), etc.
Among ISO standards, relevant standards for high-strength bolts include ISO 898-1 and ISO 898-2. ISO 898-1 specifies the mechanical property requirements for high-strength bolts, including tensile strength, yield strength, elongation, etc. ISO 898-2 specifies the requirements for dimensions and allowable tolerances of high-strength bolts.
Among ASTM standards, relevant standards for high-strength bolts include ASTM A325 and ASTM A490. These standards are mainly applicable to structural bolts, among which ASTM A325 is applicable to carbon steel materials and ASTM A490 is applicable to alloy steel materials. These standards specify the requirements for chemical composition, mechanical properties, dimensions, allowable tolerances, etc. of high-strength bolts.
It should be noted that different countries and regions may have different standards and specifications. Therefore, in practical applications, appropriate high-strength bolt standards should be selected according to the standard requirements of the country or region where they are located.
The existence of standards and specifications for high-strength bolts helps ensure the quality and reliability of bolted connections and improve the safety of engineering structures. When using high-strength bolts, they should be designed, manufactured and installed in strict accordance with the requirements of relevant standards to ensure the firmness and durability of the bolt connection.
