Inclusion Dynamics in Steelmaking Processes

Non-metallic inclusions—oxides, sulphides and complex compounds present in molten steel—play a decisive role in determining mechanical performance, surface quality and casting stability. Their formation spans deoxidation, slag-metal reactions and secondary refining steps, while their subsequent motion is governed by buoyancy, drag, interfacial tension and turbulent flow. Control of inclusion number, size and morphology is essential to prevent defects such as nozzle clogging in continuous casting, surface defects in rolled products and reductions in fatigue life. Modern steelmaking integrates thermodynamic modelling, in situ imaging and chemical control—via rare-earth or calcium treatment—to tailor inclusion populations. Advances in real-time synchrotron imaging and high-fidelity multiphase simulations now permit direct observation and prediction of inclusion trajectories during gas stirring, vacuum degassing and mould filling. Together, these tools inform process design and reagent selection, enabling steelmakers to balance cleanliness requirements with cost and environmental constraints on a global scale.

Research from Nature Portfolio

Recent studies have elucidated the impact of cerium additions on inclusion chemistry in low-carbon steels, demonstrating that precise control of S/O ratios and Ce content shifts dominant inclusion phases from manganese sulphides to cerium oxides and oxy-sulphides. Optimal Ce levels produce uniformly distributed, 4–7 µm inclusions that serve as effective heterogeneous nucleation sites for acicular ferrite, refining grain structure and enhancing toughness. Thermodynamic calculations coupled with experiment confirm the ability to predict inclusion populations and guide alloy design. Complementary efforts have applied in situ high-energy X-ray imaging during ladle processing, revealing the transient behaviour of inclusions at steel–slag interfaces and under gas-induced stirring. These dynamic observations offer quantitative data on inclusion capture, rebound and entrainment, informing the development of predictive models for inclusion removal efficiency.

Inclusion Dynamics in Steelmaking Processes publication trend

The graph below shows the total number of articles in inclusion dynamics in steelmaking processes across all publications each year (not limited to Nature Index journals).

Technical terms

Non-metallic inclusion: A non-metal compound or phase such as oxide, sulphide or oxysulphide present in steel that originates during melting or refining.

Heterogeneous nucleation: The initiation of a new solid phase on the surface of a foreign particle (inclusion) in the liquid steel, reducing the energy barrier for phase transformation.

Interfacial tension: The force per unit length at the interface between two phases (e.g. steel and slag) that influences inclusion capture and detachment.

Flotation: The buoyancy-driven rise of inclusions through the molten steel, often aided by gas bubbles, leading to removal at the slag layer.

Ladle metallurgy: Secondary refining operations conducted in a refractory-lined vessel (ladle) to adjust temperature, chemistry and inclusion content before casting.

References

1. Effect of Adding Cerium on Microstructure and Morphology of Ce-Based Inclusions Formed in Low-Carbon Steel. Scientific Reports (2017).
2. A Review of Physical and Numerical Approaches for the Study of Gas Stirring in Ladle Metallurgy. Metallurgical and Materials Transactions B (2018).
3. Significance of Nonmetallic Inclusions for the Clogging Phenomenon in Continuous Casting of Steel––A Review. Steel Research International (2022).
4. Motion Behavior of Nonmetallic Inclusions at the Interface of Steel and Slag. Part I: Model Development, Validation, and Preliminary Analysis. Metallurgical and Materials Transactions B (2016).