As the "rice of industry" in mechanical manufacturing, the standardization level of self-tapping screws is directly related to the reliability of equipment and the safety of the industrial chain. Recently, the International Organization for Standardization (ISO) and China have successively released updated standard documents in the field of self-tapping screws, comprehensively upgrading technical specifications from carbon steel to stainless steel categories. This has driven a systematic transformation in the metal fastener industry and provided core support for the high-quality development of the industry.
At the domestic standard level, the State Administration for Market Regulation officially released GB/T 3096.5-2025 "Mechanical Properties of Fasteners - Part 5: Self-tapping Screws" on October 31, 2025. This standard will come into effect on February 1, 2026, completely replacing the 2016 version of the standard. This revision is deeply integrated with international advanced technologies and formulated based on the ISO 2702:2022 international standard. The core upgrade is reflected in the precision of technical indicators and the improvement of the testing system. Compared with the old version, the new national standard has narrowed the allowable range of core hardness by 20%, clearly stipulating the stepwise requirements of surface hardness ≥700HV0.3 and core hardness 270 ~ 425HV5. At the same time, it has adjusted the maximum depth of the carburized layer to 0.15mm and added three key test procedures, providing a more scientific basis for quality control.
In the international market, the standards updated simultaneously by ISO and Europe have also drawn industry attention. Among them, the BS EN ISO 3506-3:2025 standard significantly expands the coverage of stainless steel materials. On the basis of the original austenitic stainless steel, A8 austenitic steel and D2-D8 duplex steel are included in the specification for the first time. A new hardness grade of 21H (HV≥210) is added, and the torque test procedures for hexagonal and flow-shaped grooves are improved. This standard clearly defines the applicable temperature range from -20℃ to 150℃. Among them, D4 duplex steel, with the composition advantage of "Cr+3.3Mo+16N > 24", demonstrates superior pitting corrosion resistance, meeting the demands of high-end equipment.
The upgrade of standards is driven by both the upgrading of demands in multiple fields and international trade competition. At present, the construction industry has raised its demands for the seismic resistance and corrosion resistance of screws. The automotive manufacturing industry is pursuing lightweight and high-strength components. Meanwhile, the strict requirements of the international market for standards are also forcing domestic industrial upgrading. Data shows that the annual output of fasteners in China exceeds 8.5 million tons, with self-tapping screws accounting for about 15%. However, high-end products were long dependent on imports, and the gap between the old standards and international advanced standards has become an obstacle to exports.
The pilot projects of enterprises have shown remarkable results. Data from a leading enterprise in Zhejiang Province indicates that after following the new standards for production, the one-time assembly success rate of self-tapping screws has increased from 92% to 98%, the salt spray test corrosion resistance time has been extended from 240 hours to 500 hours, and the material utilization rate has increased by 15%. More importantly, after the implementation of the new standards, the technical trade barriers for the export of self-tapping screws in China will be reduced by more than 30%. The inclusion of new materials such as duplex steel will help enterprises break through in high-end application fields such as new energy vehicles and aerospace.
At present, the industry has initiated the promotion and implementation of standards as well as technological upgrades. In the next 3 to 5 years, enterprises with backward technology will gradually be eliminated, while those with advanced production technology and quality control capabilities will occupy a larger share of the market, promoting the improvement of industry concentration and overall competitiveness, and helping China transform from a major producer of tight fasteners to a quality power.