News from China.org.cn: On January 8th, Hong Kong-Zhuhai-Macao Bridge, known as one of the “new seven wonders of the world”, applied a large number of high-performance green bridge steel based on the new generation of controlled rolling and cooling process developed by Prof. Wang Zhaodong and his research team in Northeastern University. This vividly demonstrated that Northeastern University was using the world-leading green metallurgy technology to serve the country's major strategic needs. Recently, at the 2017 National Science and Technology Award Conference, Northeastern University's project “Hot-rolled Strip Steel New Generation Controlled Rolling and Cooling Technology and Application” was awarded “second prize for national science and technology progress”.
The steel used in the bridge mainly includes pipe pile steel, bridge steel, bridge guardrail, and the ribbed bar. Among them the pipe pile steel and the bridge steel account for 60% of the total steel, and the pile steel itself accounts for about 50% of the total. Most of the material of the pipe pile steel is hot-rolled coil. The bridge steel are mainly plate products, whose specifications are between 10mm and 50mm. Northeastern University's new generation of controlled rolling and cooling technology is the representative process of the green manufacturing of hot-rolled plate strip.
The new generation of controlled rolling and cooling process developed by Professor Wang Zhaodong and his research team in Northeastern University has established a comprehensive strengthening and toughening theory on fine-grained strengthening, precipitation strengthening, and phase transformation strengthening with ultra-rapid cooling as the core. It refined the steel structure by 35% and reduced the size of the precipitated phase by more than 25%, which effectively met the demand of the bridge steel for high strength and high toughness.
Through the combination of optimized composition design，controlled rolling and ultra-rapid cooling after rolling, the team achieved a good organization ratio, which reduced the yield ratio on the basis of toughness improvement, and met the demand of earthquake resistance and strain resistance of the bridge. Relying on ultra-fast cooling equipment, the research team used online heat treatment instead of off-line normalizing heat treatment, which had significantly reduced the carbon equivalent, improved the welding performance and toughness, and solved the problems of post-welding layering, poor toughness and poor surface quality in traditional normalized bridge steel plates, thus promoting the upgrading of high-performance bridge steel standards.
China Railway Shanhaiguan Bridge Group Co., Ltd, which has long-term in-depth cooperation with Ansteel and other steel companies, has applied more than 30,000 tons of bridge steel plate with the new generation controlled rolling and cooling process developed by state key laboratory RAL in Northeastern University in various projects, including the construction of Hong Kong-Zhuhai-Macao Bridge, construction of Alaska Railway Bridge in the US， renovation of the Verrazano-Narrows Bridge，the U.S. largest suspension bridge, and the cross-sea Bridge in Dalian Puwan Economic Zone. This type of bridge steel plate showed good performance and stability, excellent toughness and welding performance, high dimensional accuracy of the steel plate, and excellent surface quality in the course of application. All the indicators of the steel plate can fully meet the requirements for the construction of ultra-long span bridge structure, which provided strong support to the bridge manufacturing industry in China and had greatly improved the international competitiveness of the industry.
It is reported that a new generation of controlled rolling and cooling technology for hot-rolled strip steel was a representative of green steel manufacturing marked with “resource conservation, energy saving and emission reduction”. The project created a new generation of controlled rolling and cooling technology system for hot-rolled steel, opened up new ways to save alloying elements and improve steel performance; created an integrated organization and control theory for hot-rolled steel, and rebuilt a green steel composition and process system. The project research team self-developed the first set of advanced rapid cooling equipment and control system for hot-rolled steel, which became the main model of hot-rolled steel production line in China. The project has also clarified the organizational evolution rules and strengthening and toughening mechanism of hot-rolled steel, and developed a series of low-cost high-performance steel material.
The research findings of Professor Wang Zhaodong and his team in Northeastern University have reduced the use of precious metals and have built China’s unique theoretical system of energy-saving steel production. These research findings were successively listed in the 16 industrial policy guideline documents issued by the Five Ministries and Commissions, including the Ministry of Science and Technology, the Ministry of Industry and Information Technology, and the National Development and Reform Commission. They have given a big bush to the energy saving and emission reduction, green transformation and upgrading of China's iron and steel industry, and have achieved the overall improvement of the performance of China's iron and steel materials, promoted the localization process of major metallurgical equipments, met the urgent needs of the national steel, and improved the country's self-guarantee capability of major equipments. At the same time, the research project has cultivated up to 100 senior personnel and professional engineering and technical experts for enterprises and society, which raised the professional level of steel manufacturing and product development in China.