A few days ago, the high-efficiency continuous casting technology of high-aluminum steel slab developed by Shougang won the First Prize for Metallurgical Science and Technology. It significantly improves slab quality and production efficiency, and realizes the continuous industrial production of high-aluminum steel. The series of high-aluminum cold-rolled high-strength steels produced by this technology have been applied by high-end joint ventures and domestic leading brand automobile enterprises in batches, providing strong support for the lightweight development of the automobile industry.

With national economic development and the upgrading of the industrial structure, high-aluminum steel is widely used in automobiles, energy, electric power and other key fields by virtue of its features including high strength, high toughness, low density and low cost. However, with the continuous upgrading of products, technical quality problems became increasingly prominent. In the continuous casting of high-aluminum steel slabs, not only did the adhesion alarm of crystallizers frequently occur, making it difficult to realize multi-furnace continuous casting, but problems such as transverse depression, cracks and broken slabs also occurred in produced slabs. Many studies and explorations were carried out at home and abroad, but the problems had not been effectively solved. The efficient mass production of high-aluminum steel slabs had become a common problem in the industry.

Facing this bottleneck problem, Dr. Ji Chenxi from the Jingtang Technology Center of the Shougang Technology Research Institute volunteered to set up a multi-disciplinary joint research team covering many units and departments including the Technology Research Institute, Jingtang Company, Beijing Shougang and University of Science and Technology Beijing. The team systematically tackled problems such as the changes of physical and chemical properties in casting powder, submerged nozzle blockages, adhesion alarm of crystallizers and slab cracks during the continuous casting of high-aluminum steel slabs.

Discussing the research process, Ji Chenxi said, “Tacking problems in technology will never be smooth, and every innovation breakthrough cannot be separated from the sincere cooperation of multiple departments and specialties. In terms of basic research, comparison of processes and technologies, slab quality control, etc., all participating units efficiently cooperated with each other in a division of labor, and Jingtang and Beijing Shougang learned relevant technologies from each other, providing a strong guarantee for the smooth development of the project.” Before each production, Jingtang's Manufacturing Department, Steelmaking Department and other relevant departments carried out a review summary together to discuss the improvement plan. During production, team members were present on site to analyze the improvement effects of process and slab quality together. Yang Chunbao, Chief Operation Officer of the Jingtang Company continuous casting operation area, and skills expert Xiao Huasheng volunteered to guide the whole operation. Yu Xuecheng from Beijing Shougang improved the uniformity of the meniscus temperature by effectively controlling the surface velocity of molten steel in the crystallizer. To solve the problem of nozzle blockage, team members Tian Guichang and Liu Yanqiang improved the alloying method and ladle slagging process, and controlled the total oxygen content of the molten steel to less than 5 ppm, providing a basic guarantee for the stable continuous casting of high-aluminum steel slabs. To address the slab crack problem, team member Liu Guoliang compared the influence of vibration modes in different crystallizers on slab quality and put forward a new control idea to ensure the uniform solidification of slab shells and secure high slab quality.

The “High-efficiency Continuous Casting of High-aluminum Steel Slab” project has been granted ten invention patents and yielded the successive development of seven key processes. For the first time, the continuous casting of high-aluminum steel slabs has been realized for five furnaces and 1,500 tons, and the casting speed has been increased from 0.8 m/min to 1.2 m/min, which has effectively solved many technical problems such as poor castability and many surface cracks in the continuous casting of high-aluminum steel slabs. The related technology of the multi-furnace continuous casting of high-aluminum steel has also been successfully applied to the continuous casting of microalloyed steel slabs, which further overcomes a series of technical problems in the production of microalloyed steel and realizes the independent integration of slab hot-charging pretreatment equipment and process technology.