Min Wang

Iron and steel are core materials for high‐end equipment and major projects; their purity, strength‐toughness, and stability matter to national economy and industrial upgrading. Non‐metallic inclusions, coarse grains, and segregation in steel bottleneck high‐quality steel development. Rare earths (Ce, La, Y) with unique 4f structure, high electronegativity and interfacial activity, higher O/S binding energy than Al, Ca, react preferentially with harmful elements to form fine spherical rare earth inclusions for deep purification and modification, segregate at boundaries to refine grains, regulate phase transformation and second‐phase distribution, optimizing steel microstructure and properties synergistically. This paper reviews rare earths’ regulatory mechanisms on steel inclusions, including basic theories, addition methods, inclusion modification, microstructure evolution, and property effects. It elaborates rare earth inclusion formation thermodynamically, summarizes mainstream addition processes’ scenarios and key points, analyzes their effects on typical inclusion regulation, and reveals grain refinement and phase transformation laws. Finally, it summarizes rare earths’ effects on steel’s mechanical, corrosion and creep resistance, prospects their microalloying for high‐quality steel, providing theoretical and technical support for rare earth steel industrial production.

Explosions caused by unintended contact between leaked molten aluminum and water represent a core safety hazard restricting safe production in direct chill (DC) casting across the aluminum processing industry. In recent years, molten aluminum–water explosion accidents have occurred frequently in DC casting facilities, creating an urgent demand for targeted risk management and control. Clarifying the mechanism of molten aluminum–water explosions is a critical prerequisite for developing explosion prevention technologies. This paper systematically reviews the mechanisms, key influencing factors, and cutting‐edge prevention and control technologies for molten aluminum–water explosions in DC casting. Such explosions are essentially physicochemical coupled events dominated by physical explosion mechanisms. Even when only 3%–6% of the molten aluminum reacts with water, the hydrogen generated can significantly amplify explosion intensity, and the overall process exhibits distinct staged kinetic characteristics. This review clarifies the governing rules of key influencing parameters, the correlation between explosion intensity levels and hazard severity, and the remaining gaps in current theoretical research. It also summarizes the advantages and application limitations of existing prevention and control technologies, pointing out that single monitoring or protection measures have notable inherent shortcomings. The research indicates that an integrated multi‐technology prevention and control system delivers synergistic effects. Intelligent, integrated technical solutions represent a key future direction for DC casting explosion prevention and control. This review provides theoretical support for advancing the intrinsic safety level of the industry.

For the first time, a 75-kg-scale simulation experiment on molten aluminum leakage and contact with water was conducted at a direct chill casting site for aluminum processing. The study provided an in-depth analysis of the intrinsic relationship between the phenomena of molten aluminum-water interaction and the characteristics of the resulting products under real-world operating conditions. In the early stages of interaction, the metastable vapor film on the molten aluminum surface initially sustains film boiling. Subsequently, influenced by Kelvin-Helmholtz and Rayleigh-Taylor instabilities, the film collapses, causing direct contact between the molten aluminum and water. This results in the formation of a large-area medium and high-temperature zone, with peak temperatures reaching 365.6℃. During this process, the peak concentration of hydrogen gas generated by chemical reactions can reach 289.1 ppm. Typical morphologies of the solidification products include dense aggregates, wrinkled flakes, porous and loose structures, and hollow spheres; Al2O3 is a representative chemical reaction product, distributed on the surface layer of the solidification products with a thickness ranging from 1.26 to 25.85 μm, covering 0.06% to 5.19% of the matrix area. The high-speed impact of the molten aluminum jet, the collapse and rupture of the vapor film, the violent evaporation of high-temperature water vapor, and the turbulence caused by splashing molten aluminum droplets all generate a large amount of high-frequency acoustic components above 10,000 Hz, which can serve as core acoustic features for identifying molten aluminum leakage and contact with water.