How does high-purity ferrosilicon reduce inclusion formation and improve rolling performance?
Publish Time: 2025-11-21
In the field of special steel smelting, the purity of steel directly determines its final mechanical properties, processing performance, and service life. Non-metallic inclusions—such as oxides, sulfides, and silicates—are key negative factors affecting steel quality. They not only disrupt the continuity of the metal matrix, becoming fatigue crack initiators, but also cause cracking, delamination, and surface defects during hot or cold rolling, severely restricting the yield and application reliability of high-end steel. High-purity ferrosilicon, as a low-impurity ferrosilicon alloy, plays an irreplaceable role in deoxidation and alloying processes. Its high purity and compositional stability are the core guarantee for inhibiting inclusion formation and optimizing rolling performance from the source.1. Source control of impurities: Low impurity content reduces the introduction of foreign inclusionsOrdinary ferrosilicon often contains high levels of aluminum, calcium, phosphorus, sulfur, carbon, and gaseous elements. These impurities readily react with oxygen and sulfur in the molten steel to form complex oxides and other solid inclusions. High-purity ferrosilicon, through refining processes, controls impurity elements to extremely low levels, fundamentally reducing the "seed" source of foreign inclusions. When added to molten steel as a deoxidizer, it primarily generates easily floatable and removable low-melting-point FeO-SiO₂ silicates, rather than high-melting-point, difficult-to-deform rigid inclusions, significantly reducing the total oxygen content and inclusion density in the steel.2. Promoting Inclusion Modification: Enhancing Plasticity and Rolling AdaptabilityEven a small amount of residual inclusions has a significant impact on rolling performance due to their morphology and distribution. High-purity ferrosilicon, lacking strong deoxidizing elements such as aluminum and calcium, avoids the formation of high-hardness Al₂O₃ clusters—inclusions that easily lead to stress concentration and microcracks during rolling. Simultaneously, the silicon in the ferrosilicon synergistically interacts with the manganese in the steel, promoting the precipitation of sulfides in the form of fine, dispersed MnS, rather than a coarse FeS network structure. More importantly, under specific compositional control, residual inclusions can be "transformed" into low-melting-point, thermoplastic composite silicates. These inclusions are liquid or semi-liquid at the high temperatures of hot rolling, and can extend and deform synchronously with the metal matrix without breaking grain boundaries, thus significantly improving the hot working properties of the steel and reducing surface defects such as edge cracks and folds.3. Uniform and stable composition ensures controllability of the smelting processHigh-purity ferrosilicon not only has high purity, but its silicon content also fluctuates very little, exhibiting excellent batch-to-batch consistency. This makes the deoxidation reaction during steelmaking more predictable, avoiding insufficient or excessive deoxidation due to fluctuations in ferrosilicon composition. Stable silicon yield also facilitates precise control of the final steel composition, reducing subsequent refining adjustments, shortening the smelting cycle, and indirectly reducing the risk of secondary oxidation. Precise compositional control lays the foundation for obtaining a clean and uniform billet microstructure, and a uniform microstructure is a prerequisite for successful rolling.4. Enhancing Steel Purity and Indirectly Optimizing Cold Rolling and Deep Drawing PerformanceFor high-end products such as electrical steel and automotive steel sheets that require cold rolling or deep drawing, inclusion control is crucial. High-purity ferrosilicon helps produce low-inclusion steel, which is less prone to pinholes, peeling, or strip breakage during cold rolling; during annealing, it also prevents inclusions from inducing abnormal grain growth or magnetic domain pinning. The final product not only has a high surface finish but also significantly improved deep-drawing performance indicators such as elongation and r-value, meeting stringent subsequent processing requirements.The value of high-purity ferrosilicon goes far beyond providing silicon. Through a four-pronged mechanism of "low impurity input—inclusion reduction—morphology optimization—composition stabilization," it constructs the first line of defense for clean steel production from the source of smelting. In the modern steel industry, which pursues high performance, high yield, and high reliability, this seemingly ordinary alloying additive is actually a key "invisible driver" for improving rolling smoothness and expanding the boundaries of high-end products. Choosing high-purity ferrosilicon means choosing a pure foundation for steel's toughness.
