In the modern steelmaking process, continuous casting is not only the link between steelmaking and rolling, but also the determining factor for the entire production line’s capacity. With the establishment of the goal of achieving a daily output of over 10,000 tons in the new steelmaking system, the continuous casting process must transform from traditional “stable operation” to an integrated industrial model characterized by “high speed, high quality, and long service life.”
For a large-scale production system with a daily steel output exceeding 10,035 tons, the stability of the casting speed and the effective operating rate of the continuous casting machine are crucial factors determining overall performance.
- High casting speed: Increasing the casting speed by just 0.1 m/min places exponential demands on the mold liquid level stability, the uniformity of billet solidification, and the mechanical precision of the equipment.
- System: Improving efficiency in the continuous casting process involves not only increasing the output of individual equipment, but more importantly, shortening the turnaround time and reducing the waiting time of molten steel in the refining process, thereby achieving precise control of temperature drop throughout the entire process.
Dynamic optimization of the secondary cooling water system
The secondary cooling zone is the core region for the solidification of the cast billet. Under high casting speeds, the traditional “empirical water flow method” can no longer meet the requirements for crack control and central segregation.
1. Construction of a dynamic cooling model
By introducing a dynamic secondary cooling water distribution model based on real-time pulling speed, steel grade superheating, and solidification end position, the technical team reconstructed the cooling curve. For wide and thin slabs or special steels, a gradient distribution of “strong cooling transitioning to weak cooling” was adopted to ensure that the surface temperature of the cast slab remains in the good plasticity range (usually above 900°C) in the straightening zone, effectively avoiding transverse cracks caused by stress concentration.
2. Fluid simulation of nozzle arrangement and water distribution
The procurement and technical departments collaborated to introduce high-precision atomizing nozzles. Through fluid dynamics simulation optimization, uniform coverage across the entire width of the cast slab was achieved.
Technical specifications: Cooling uniformity error is controlled within ±5%.
Monitoring upgrade: Implementing integrated online monitoring of water pressure, flow rate, and water temperature to ensure that fluctuations in the cooling system are detected and compensated for within seconds.
Casting mold flow field control under high casting speed conditions
The crystallizer is the “heart” of the continuous casting machine. At high casting speeds, balancing the energy distribution of the molten steel flow is crucial for preventing breakouts and improving surface quality.
- Protective slag performance matching: The procurement department should focus on selecting protective slag with “low viscosity, high melting rate, and excellent lubrication” for high-speed casting processes.
- Automatic mold level control (ALC): By introducing electromagnetic braking (EMBr) technology, the impact of molten steel on the narrow faces of the mold at high casting speeds is reduced, thereby minimizing liquid level fluctuations.
- Vibration parameter optimization: A high-frequency, small-amplitude non-sinusoidal vibration mode is used to reduce the depth of vibration marks, providing a high-quality base for subsequent hot assembly and transfer processes.
Standardized Operations and Equipment Reliability Assurance
1. Deep integration of Standard Operating Procedures (SOPs)
Rigorous standardized operating procedures have been established for the “four key stages” of the continuous casting process (start of casting, strand connection, ladle change, and casting termination). In particular, the control of molten steel superheating is required to be within a fluctuation range of ±5°C.
2. Lifecycle management of critical spare parts (procurement focus)
For procurement personnel, improving efficiency means demanding higher standards for the lifespan of critical wear parts:
Submerged Entry Nozzle (SEN): The main considerations are erosion resistance and clog prevention, ensuring stability during long continuous casting periods.
Foot rollers and sector segment rollers: High-hardness overlay welding technology is introduced to improve the wear resistance and thermal fatigue resistance of the roller surface, extending the overall replacement cycle of the sector segments.
Achieving “zero waiting time” in the smelting, casting, and rolling processes.
Improving efficiency is not only about what happens within the machine, but also what happens outside of it.
Rhythm coordination: By operating the continuous casting machine at a constant casting speed, the process standardizes the rhythm of the converter and refining processes. Utilizing an intelligent scheduling system, the idle time of the ladle on the overhead crane is reduced by more than 15%.
Increased yield: By optimizing continuous casting technology for different steel grades and controlling the amount of residual steel in the tundish, head and tail losses are minimized, resulting in an overall metal yield increase of more than 0.5%.
The long-term stable operation of the continuous casting process under high casting speeds is the “final step” in unleashing the production capacity of the new steelmaking system. Through the refined optimization of the secondary cooling system, precise control of the mold flow field, and ensuring high-quality refractory materials from the supply chain, not only was the production limit of 10,035 tons surpassed, but a scientific governance system for digital steelmaking was also established.
Why is increasing the pulling speed crucial for achieving a breakthrough in production capacity?
With a fixed number of continuous casting machines, the casting speed is the only variable affecting the output per unit of time. A higher casting speed means a shorter molten steel turnover cycle, which can significantly reduce the overall temperature drop in the steelmaking system and unleash the potential of the upstream converters.
In secondary cooling water optimization, how can we balance cooling speed with the risk of cracking?
Through a dynamic cooling model, at high casting speeds, the focus is not simply on increasing the water volume, but on achieving “uniform cooling.” Mist cooling technology ensures a gradual temperature drop on the surface of the cast billet, avoiding the brittle temperature range of the steel grade.
What are the specific requirements for the physicochemical properties of the protective slag under high casting speeds?
High casting speeds require the protective slag to have a faster melting rate to maintain the liquid slag layer thickness, and also require low viscosity to ensure it flows into the gap between the billet shell and the mold, providing good lubrication and heat transfer.
How can we reduce unplanned slowdowns and shutdowns?
This approach primarily relies on online monitoring of key parameters (such as crystallizer heat flow monitoring and friction force monitoring) and predictive maintenance of equipment (such as vibration table mechanical clearance inspection) to eliminate potential sudden failure risks.
How does purchasing high-quality immersion nozzles (SENs) affect costs?
Although the cost per unit may increase, the extended lifespan reduces production losses due to slowdowns or stoppages caused by nozzle replacement, resulting in a significant decrease in the overall cost per ton of steel.
