Key Technologies and Equipment for Molten Steel Cooling and Solidification in Continuous Casting
Continuous Casting Steel Cooling and Solidification: Key Technologies and Equipment for the Transition from Experience-Based Casting to Precision Control
In the integrated steel production chain, the continuous casting process occupies a central position, and the cooling and solidification of molten steel is the core stage that determines billet quality-. Molten steel in a continuous casting machine undergoes primary cooling in the mold, spray cooling in the secondary cooling zone, and soft reduction at the solidification end before completing the liquid-to-solid phase transformation during continuous motion. This process involves the coupling of multiple physical fields—heat transfer, fluid flow, solidification, and stress—and the precision of cooling regime design and execution directly determines whether internal defects such as center segregation, porosity, and cracks will occur, ultimately affecting the performance and reliability of finished steel products.
Primary Mold Cooling and Electromagnetic Stirring
After molten steel is poured through the tundish into the mold, a primary shell forms under the forced water cooling of the copper mold wall. The mold serves as the “heart” of the continuous casting machine, and the size and position of its cooling water channels must be precisely designed through numerical simulation to ensure uniform shell thickness for billets of complex cross-sections-. Meanwhile, mold flux forms a slag film on the molten steel surface, playing a critical role in regulating lubrication and heat transfer-.
Mold electromagnetic stirring (M-EMS) is a core technology for optimizing the initial solidification structure. By applying an alternating magnetic field in the mold region, this technology drives rotational flow of molten steel, accelerates superheat dissipation, increases the nucleation rate of equiaxed crystals, and expands the equiaxed crystal zone, thereby effectively improving center segregation-. In 2025, Baosight Software, relying on the Digital-Intelligence Technology Innovation Center of Baosteel’s Central Research Institute, successfully deployed a wide-thick slab mold electromagnetic stirring flow control device at Zhanjiang Iron & Steel’s 2700mm wide-thick slab caster. Through innovative design of arched core coils and reinforced mold jacket support structures, a uniform and strong magnetic field environment was achieved across ultra-wide cross-sections, with thick plate flaw detection degradation rate, bubble degradation rate, and hot-rolled slag entrapment block rate all reduced by more than 30%. Since 2004, the Baosight R&D team has continuously promoted the industrialization of electromagnetic metallurgy technology, from conventional slabs to ultra-wide thick slabs.
Dynamic Precision Control in the Secondary Cooling Zone
After the strand exits the mold, it enters the secondary cooling zone where the shell is still thin and requires continued spray cooling to accelerate solidification. The secondary cooling zone is typically divided into foot roll, segment 2, segment 3, and subsequent cooling sections, using air-mist cooling with specific water ratios set according to steel grade and casting speed-. Inappropriate secondary cooling intensity can induce surface depressions, cracks, or even breakout accidents, making dynamic water distribution control a key focus of industry research.
Three-dimensional secondary cooling water dynamic control technology tracks the temperature field distribution of the strand in real time during continuous casting, enabling dynamic optimization of the cooling process. Based on precise numerical models and intelligent control algorithms, this technology not only improves strand quality but also significantly reduces the probability of surface cracks and center defects, demonstrating particular advantages in producing crack-sensitive steel grades. Primetals Technologies’ Dynacs 3D secondary cooling model predicts the complete 3D temperature distribution at any position along the strand, optimizes secondary cooling setpoints, and displays the final solidification point to support precise control-. This technology has been successfully applied in multiple projects, including a six-strand bloom caster for Wuhan Iron and Steel Co., Ltd. Additionally, Danieli’s Q-COOL system, based on a solidification model, formulates differentiated cooling strategies according to steel grade properties and adjusts cooling water flow in real time to ensure ideal surface temperature and solidification profile-.
Synergistic Application of Final Electromagnetic Stirring and Soft Reduction
When the strand reaches the final solidification zone, the enriched solute liquid steel in the central liquid pool flows naturally under static pressure, which is the root cause of center segregation and porosity. The synergistic application of electromagnetic stirring and soft reduction has become the most effective means of improving internal billet quality.
Final electromagnetic stirrers (F-EMS) are typically installed in the region where the solidification fraction of the continuous casting billet is 20%–32%, strengthening molten steel movement by inducing electromagnetic force in the liquid pool, improving dendrite fragmentation capability, and promoting equiaxed crystal formation-. Meanwhile, final soft reduction technology applies a certain reduction amount near the solidification end of the strand, disrupting the liquid pool and suppressing the movement of enriched molten steel along the casting direction, thereby significantly improving center segregation and porosity-. The segment products supplied by CISDI for Jiuquan Iron & Steel’s steelmaking and rolling project apply advanced technologies including “continuous bending and continuous straightening variable roll diameter roll arrangement” and “high roll gap precision segments,” achieving quality targets of “center segregation superior to B0.5 in ≥95% of billets” and “no internal cracks ≥1.0 grade”-.
New Advances in Intelligent and Multi-Mode Cooling Control
With the deep integration of artificial intelligence and industrial internet technologies, continuous casting cooling control is transitioning from traditional empirical models to data-driven intelligent control. The research team led by Professor Liu Qing at the University of Science and Technology Beijing innovatively proposed multi-mode continuous casting cooling control technology based on the solidification characteristics of different steel grades, developed key new technologies including second-phase precipitation characterization, and achieved precise control of the solidification process and structure for clean, efficient, and green customized production of high-end steel-. Since 2019, USTB and Nanjing Iron & Steel Co., Ltd. have jointly established a Continuous Casting Solidification and Cooling Control Technology Joint Research Center, and in 2026 further established the “High-Quality Steel Green Intelligent Metallurgy Joint Research Center,” focusing on steelmaking-continuous casting process optimization and digital intelligent metallurgy.
In the field of industrial cooling system optimization, Primetals Technologies launched a new heat-transfer test facility in December 2025, enabling real-time visualization of the hot strand during continuous casting cooling through innovative visualization technology. The flexible setup allows testing of any type of industrial cooling system, providing an advanced experimental platform for continuous improvement of cooling processes-. Hebei Iron and Steel Group has also adopted a slab caster from Primetals, using the Dynacs 3D model to achieve optimal adjustment of secondary cooling setpoints and the final solidification point-.
From mold electromagnetic stirring to dynamic secondary cooling water distribution, from multi-roll synergistic soft reduction at the solidification end to AI-based multi-mode cooling control, continuous casting steel cooling and solidification technology is steadily advancing toward precision, intelligence, and green development. Continuous casting technology has significantly promoted high-quality, high-efficiency, and green production in the steel industry, with homogeneity, stability, and efficiency becoming the primary indicators for high-quality continuous casting billet production-. With the continuous breakthrough and application of key technologies such as wide-thick slab electromagnetic stirring, 3D secondary cooling dynamic control, and precise final solidification reduction, steel enterprises will further enhance the quality competitiveness of high-end products, providing more reliable quality steel for key sectors including shipbuilding, energy, and major equipment manufacturing.