The 2024 Metallurgical Science and Technology Award Grand Prize was awarded to Shougang Jingtang’s MCCR Multi-mode Continuous Casting and Rolling Technology Integration and Innovation project. The casting and rolling integration technology is a major advancement in the technology of the interface of the iron and steel manufacturing process.
Mr. Wang Guolian, Secretary of the Party Committee of Steel Rolling Department of Shougang Jingtang Company, shared this technology at the 4th National Steel Industry “New Knowledge, New Technology, New Idea” Exchange Conference.
Wang Guolian introduced the evolution of the steel manufacturing process from intermittent to quasi-continuous or even continuous transition. Thin slab continuous casting and rolling as a representative of the near-final shape of the manufacturing technology, is the optimization of the steel manufacturing process, an important direction of reconstruction, is to achieve low-carbon, efficient production of high-strength thin specifications of one of the main ways of strip steel. Thin slab continuous casting and rolling technology for more than 30 years after three generations of development, the formation of CSP, FTSR, ISP, CEM, ESP and other forms of technology. The third-generation technology represented by ESP adopts headless rolling, which can stabilize the production of thin specification products. “The third-generation technology realizes full continuous headless rolling with hot continuous rolling with high drawing speed and high steel flux of continuous casting, which is called the integration of full continuous casting and rolling of thin slabs.” Shougang develops a new third-generation thin slab continuous casting and rolling technology, i.e., multi-mode fully continuous casting and rolling production line, the production line adopts the latest technology and a new layout, with the goal of realizing the flexible production of multiple varieties and specifications under the condition of high steel flux, and making the quality of products better. BSIET has overcome technical problems such as flexible production of multiple varieties and specifications, continuous casting of all varieties with high steel flux, efficient and low-cost smelting of ultra-clean steel, and high-precision quality control under long roll period by carrying out innovation of process technology and equipment.
This project has realized four innovations: First, the first single billet/semi-headless/full headless rolling multi-mode thin slab full continuous casting and rolling integration technology. For the first time, the project set up a multi-functional tunnel-type even-heat furnace in the headless rolling production line, developed key technologies such as online width adjustment of the headless rolling mode and rolling control strategies for different modes, realized flexible production of multiple varieties, multiple widths, multiple rolling modes and multiple roll periods for a single casting, and the integrated yield rate of steel to coil reached 98.7%, the amount of online width adjustment of the headless rolling mode reached 80 mm, and the ratio of headless rolling reached More than 96%. Secondly, it is the first time to put forward the concept of “steel flux index”, and establish the control technology system of thin slab continuous casting with high drawing speed and high steel flux. Shougang led the design of “small roll diameter, variable roll spacing” roll column and “L” type water tank strong cooling crystallizer, developed a five-hole island structure immersed in the water mouth, crystallizer flow field precision control, high lubrication and heat control slag protection, laser 3D printing of copper plate repair and other key technologies, to achieve the highest 110 mm casting billet. The maximum pulling speed of 110mm billet is 6.0m/min, the “steel flux index” reaches 660mm-m/min, and the hit rate of crystallizer liquid level ≤±3mm is 99.8%. Third, the first “KR-BOF-VD-LF-MCCR” and “KR-BOF-LF-(VD)-MCCR” process routes. The project developed VD accurate decarburization, anti-silicon and high sulfur capacity slag system and efficient deep desulfurization and other key technologies, to achieve ≤ 0.03% low silicon, ≤ 0.0020% ultra-low sulfur, ≤ 0.01% ultra-low carbon series of steel grades and T [O] ≤ 0.001% of ultra-clean steel efficient and stable production of LF-VD double refining for steel supply cycle is as low as 29 minutes to meet the requirements of the high-steel flux casting and long-cycle continuous pouring. Fourthly, it is the first time to put forward the dynamic and precise coupling control strategy of thin and wide strip steel quality under the long roll period. The project developed a headless rolling mode roughing and finishing rolling convexity double closed loop, iron oxide and performance consistency control and other key technologies. The project has achieved 98.5% convexity hitting rate of all headless rolled strip, 264 km rolling mileage in single roll period, stable production of 1500 MPa high-strength steel, and fluctuation of performance of Gipa-grade thin-gauge high-strength steel with the same specification ≤±30 MPa.
Multi-mode full continuous casting and rolling production line has solved a series of problems such as production stability of thin-gauge high-strength products, plate shape control, flat rolls, etc. SHR780/980MS, HR1200/1800HS, SQ550FRW and other grades of products of 1.3 mm and below have realized the exclusive supply of Shougang. It was assessed that the overall results of the project reached the international leading level. The technology has been stably applied in the MCCR production line of Shougang Jingtang, which has cumulatively produced 5.361 million tons of high-quality, thin and wide-gauge hot and wide strip steel in the past three years, and realized 594,700 tons of carbon reduction in the process, etc. The technologies of cast billet thickening, online widening at high drawing speed, transverse magnetic induction heating, and multi-point descaling, etc., which were firstly applied by the integrated technology of multi-mode continuous casting and rolling of MCCR, have been applied to the newly built lines in the past few years.
Wang Guolian believes that the integration of full continuous casting and rolling and headless rolling technology has a qualitative difference at different levels. From the sense of process, headless rolling is the process of internal technology upgrades, while casting and rolling integration technology is a major advancement in the interface technology of the steel manufacturing process, is the process of structural reconstruction and upgrading. The continuous casting – rolling interface from the main interface of the traditional process into a “sub-interface” or even “no interface”, realizing the full continuous production from molten steel to steel coils, so that the production process of plate and strip from “semi-continuous” “quasi-continuous “Quasi-continuous” evolved into ‘fully continuous’. From the variety of quality level, the main goal of headless rolling is to produce thin specification products, and casting and rolling integration is not only can produce thin specification strip products, but also due to the continuous casting from the pulling speed to the strip rolling speed, temperature, tension are constant, so that the product dimensional accuracy, the quality of the plate shape have been greatly improved. Conventional continuous casting – hot rolling production line is located in the production of high cleanliness, high surface requirements of high-end cold rolled base material (such as automotive panels), high grade silicon steel, thick specification plates and coils (such as pipeline steel), as well as small quantities of difficult to pour, difficult to roll varieties, suitable for docking blast furnace – converter long process. The new generation of double-stream thin slab continuous casting and rolling line is located in the production of large quantities of ordinary hot-rolled products (including medium and low grade silicon steel), mainly single billet rolling, can be considered semi-headless rolling (not the pursuit of thin specifications, is conducive to the rate of formation and shape control), can be docked to the long process of the blast furnace-converter, and is more suitable for the short process of the electric furnace. The integrated thin slab casting and rolling line is positioned to produce thin specification “heat instead of cold” products; thin specification high-strength steel; medium and high carbon “low segregation” products.
With the continuous upgrading of the technology, the quality of products produced by the integrated thin slab casting and rolling technology can replace conventional hot-rolled products and some cold-rolled products in the majority of applications, with higher yield and lower production costs, realizing the goal of producing “greener products” with “more ecological processes”.
