Material selection serves as the fundamental technical basis for fasteners, particularly high-strength fasteners used in the automotive industry. Common materials include low-carbon steel (e.g., 08A, 10A), medium-carbon steel (e.g., grades 35 and 45), alloy steel (e.g., 35CrMoA, 42CrMoA, 10B21), and stainless steel (e.g., SUS304, SUS316).
Driven by the demand for lightweighting, the application of high-strength steel, aluminum alloys, titanium alloys, and composite materials is continuously expanding.
Heat treatment is a critical technology for controlling fastener performance and ensuring longevity, safety, and reliability-especially for high-strength bolts of grade 8.8 and above. Quenching and tempering treatments significantly enhance the material's tensile strength, yield strength, and impact toughness. Metallographic inspection is a vital method for ensuring heat treatment quality; it is used to analyze the material's internal microstructure and verify that the core of the threaded section achieves the required martensitic structure.
Surface treatment technologies are selected based on product aesthetics, operating environments, and corrosion resistance requirements. Key methods include oxidation, electro-galvanizing, and coating processes such as Dacromet, Geomet, and electrophoresis. Technological trends are shifting toward eco-friendly, high-performance solutions, including nano-coatings, dry-film lubrication, and highly corrosion-resistant coatings.
Intelligent manufacturing enables digital traceability in the fastening process. Through torque monitoring and data acquisition, enterprises can monitor assembly status in real-time and implement comprehensive quality control spanning the entire lifecycle from production to maintenance. Primary assembly methods include torque control and torque-angle control.
Automotive fastening technology is rapidly evolving toward high strength, lightweighting, functional integration, and intelligence. For new energy vehicles, battery pack safety requirements have set new standards for anti-loosening designs and assembly precision, driving the development of innovative solutions such as pre-applied adhesives and anti-rotation structures. Shape-memory alloy fasteners hold potential for application in critical areas of new energy vehicles due to their excellent anti-loosening properties.