Recently, the online hot-rolled seamless steel pipe cooling equipment and automation control system developed by Professor Yuan Guo’s research team in Northeastern University has successfully completed functional assessment and met the expected goal at Baosteel, marking the success of China's first set of on-line control and cooling system of hot-rolled seamless steel pipe with both accurate control on final cooling temperature and direct quenching function. Meanwhile, Baosteel has also become the first enterprise in the world to master this cooling-control technology and put it into industrial application. Seamless steel pipes are widely used in various liquid and gas transmission pipelines due to their hollow-closed structure and great bending and torsional strength. As one of the important raw materials for the construction of national economy, it is also used in various machine components and building structures.
China is a large producer and consumer of hot-rolled seamless steel pipes, but the current product structure and performance control process lacks diversity, and it is too dependent on the addition of alloying elements and off-line heat treatment to meet the relevant mechanical properties. Meanwhile, with serious product homogeneity, high cost, high energy consumption and long production cycle, the seamless steel pipe industry calls for key technological innovations and breakthroughs, the development of characteristic high-performance products, energy saving and consumption reduction measures, and the improvement of product quality and efficiency of seamless steel pipes.
The cooling control technology, which improves the organization and performance of steel by controlling the cooling rate and path after rolling, has been widely used in the fields of steel plate, strip, wire, etc, and has played a key role in product organization and control, product performance improvement, and development of high-performance products with unique features. However, due to the circular-section feature of steel pipes, its high-intensity homogenization cooling mechanism is significantly different from the above-mentioned steel types. Many research institutes and enterprises both at home and abroad have carried out a lot of basic research and technological research, but they failed to tackle the technical problems due to uneven cooling, insufficient cooling strength, and bending and deformation of steel pipes after cooling. So far the industrial application of cooling control technology in the field of hot-rolled seamless steel pipes has remained blank, which becomes a bottleneck that constrains the green production of steel pipes and the development of advanced techniques to produce high-quality hot-rolled seamless steel pipes.
In order to solve the technical problems in this industry and break through the predicament of vicious competition among homogenizations of hot-rolled seamless steel pipes, Prof. Yuan Guo and his research team in state key laboratory RAL of Northeastern University carried out in-depth research on the cooling mechanism based on the circular section of steel pipes, and finally achieved a high-strength homogenization heat exchange system and control method in the cooling process of the steel pipes. Relying on this technology, the research team cooperated with Baosteel and collaborated on innovation to carry out scientific research in the development of online cooling control equipments of hot rolled seamless steel pipes. In 2014, they developed an online cooling control pilot device based on the PQF460 hot-rolled seamless steel pipe production line in Baosteel, and conducted multiple rounds of technical research and pilot tests. Based on these works, they developed the first set of on-line cooling control equipment platform for hot rolled seamless steel pipes with precise temperature control in China, and succeeded in the heat load test run in April 2016.
The project team, in cooperation with the Research Institute and Tube, Pipe and Bar Department in BaoSteel, has tackled a series of technical problems successively, such as high-intensity homogenization cooling mechanism for circular steel section, key equipment technology development, and precise control of steel grades and supporting process strategies. The cooling control equipment and technology of hot-rolled seamless steel pipes have achieved good results since they were put into industrial application, with high precision of temperature control after cooling, good homogenization and shape of steel pipes after cooling. Meanwhile, the manufacturing cost per ton of steel was reduced by an average of 200 yuan or more and the energy consumption dropped by more than 20%.
Up to now, Baosteel has used this equipment and process to produce more than 60,000 tons of hot-rolled seamless steel pipes accumulatively. The product performance has been significantly improved, and the alloying and process reduction effect has been remarkable. It is of great significance to the construction of technology development platform of hot-rolled seamless steel pipes, and to the promotion of technological progress of hot rolled seamless steel pipe products in China.
