Recently, the development project of high-performance earthquake-resistant, fire-resistant and weather-resistant steel and its supporting connection technology led by Shougang successfully completed the comprehensive R&D of products and technologies, and realized many engineering applications. This achievement is of great significance for promoting the upgrading of steel products for construction in China and realizing the transformation from single function to compound functions.

Steel structure buildings have many advantages such as strong earthquake resistance capacity, short construction period, rich design forms, flexible spatial layout, long service life and recyclability. The output of steel in China has ranked first in the world for 23 consecutive years since 1997, but the proportion of steel structure buildings in China is only about 6%, representing a large gap compared with major developed countries. In 2016, the State Council successively issued a series of documents such as the Several Opinions on Further Strengthening the Management of Urban Planning and Construction and Guiding Opinions on Vigorously Developing Fabricated Buildings, and put forward suggestions on vigorously developing steel structure buildings, hoping to make fabricated buildings account for 30% of new buildings in about ten years. However, steel structure buildings also face their own limitations in popularization and application, and the poor resistance to corrosion and fire of ordinary steel structures have become the main restraining factors. Therefore, after the processing of steel structures in general buildings, it is necessary to meet the requirements of anti-corrosion performance and fire resistance through three processes: shot peening, spraying with anti-corrosion primer and intermediate paint, and spraying with fire retardant coating. However, the spraying process will inevitably bring serious dust and VOC pollution, which is contrary to the new development concepts of going green and low carbon. Meanwhile, the treatment process will also significantly increase the production process and environmental protection cost of steel structure processing enterprises, and reduce processing and construction efficiency.

In order to solve the above problems, it is urgently necessary to develop a new generation of functional composite building structural steel integrating multiple performances such as earthquake resistance, fire resistance and weather resistance. In 2017, the key R&D plan of the Ministry of Science and Technology, Earthquake-Resistant, Corrosion-Resistant and Fire-Resistant Steel for Building Structures, led by the China Iron & Steel Research Institute and University of Science and Technology Beijing, was launched. As the leading unit of the program Research on Stabilized Production and Application of 460MPa Earthquake-Resistant, Corrosion-Resistant and Fire-Resistant Steel Plates and Profile Steel, the Shougang Group united with Nanyang Hanye Special Steel Co., Ltd., Ma’anshan Iron and Steel Co., Ltd. and others to form a research team to carry out the R&D of high-performance earthquake-resistant, fire-resistant and weather-resistant steel and supporting connection technology.

At that time, the highest strength of fire-resistant and weather-resistant steel that had been demonstrated and applied in China was only 390MPa, and the key manufacturing technology of 460MPa fire-resistant and weather-resistant steel for buildings was still lacking. The R&D team started to tackle key technical problems from the whole process of composition design, steelmaking process, rolling and heat treatment. Emphasis was placed on the optimization design of low-cost alloy components, smelting technology for the selective control and modified treatment of occluded foreign substances, precise rolling and cooling, and other key technical problems. A composite strengthening mechanism was innovatively used to comprehensively realize the multiple performance coupling of 460MPa fire-resistant and weather-resistant steel for buildings in fire resistance, weather resistance, high strength and toughness, low yield ratio and so on. The thickness of trial-manufactured steel plates reached 150 mm, and that of hot rolled H-shaped steel reached 100 mm.

Under the condition of being ignited, the original bearing mode of matching bolt joints connected to fire-resistant and weather-resistant steel will be disabled, and the structure will change. Therefore, it is necessary to form a matching method between the strength of matching plates and the fire resistance of bolts under high temperature conditions according to the design specifications. In the absence of products, standards and specifications for reference, the R&D team independently designed the components and solved the matching of fire resistance, weather resistance and self-corrosion in 460MPa plates based on meeting a large number of its own properties, and successfully formed matching. Meanwhile, the delayed breaking problem of high-strength bolts in harsh hydrogen environments was solved by technical means, and its delayed breaking strength was increased by more than 30%, which met the technical requirements of the project. In addition, the matching welding materials for the connection of rolled steel had to simultaneously meet the multi-performance coupling of earthquake resistance, fire resistance, weather resistance and high strength and toughness. However, it was found in practice that common weather-resistant elements are sensitive to the welding process, which makes the welding process window smaller and may even damage the impact toughness. After several rounds of technical tests, the R&D team successfully realized the development of matching welding materials by changing the composition and adjusting the mixture ratio, which met the comprehensive performance requirements for welded joints in engineering application and filled in the gap of matching welding material products for 460MPa fire-resistant and weather-resistant steel. The series of 345MPa, 460MPa and 550MPa high-performance earthquake-resistant, fire-resistant and weather-resistant steel and supporting connection technology developed by Shougang has successfully passed anti-corrosion and fire-proof demonstration at the Shougang Jingtang Phase II Deacidification and Ammonia Distillation Plant, and a fire-proof coating demonstration has been made for large-scale steel structure projects such as the referee tower of the ski jump platform for the 2022 Beijing Winter Olympics and the Nantong International Convention & Exhibition Center. Based on this technology, the national standard Fire-resistant and Weather-Resistant Structural Steel compiled by Shougang as the leader has been unanimously approved by the expert group, and the comprehensive technical level has reached the international advanced level, providing strong technical support for the application of fire-resistant and weather-resistant structural steel in China.

The use of nude-packed fire-resistant and weather-resistant steel structures reduces the steps of anti-corrosion and fire-proof spraying, which is not only greener and more environmentally friendly, but can also effectively improve their fire safety and service life. This has huge promotion potential in steel structure residential buildings, three-dimensional garages, public buildings and other fields. The development and application of high-performance earthquake-resistant, fire-resistant and weather-resistant steel and its supporting connection technology are in line with the important development direction of steel for building structures in China, and provide Shougang’s solutions for efficient and green development.