The initial production phase for silicon steel coils and sheets relies on refining and hot rolling; these steps determine material purity and the base microstructure, serving as the primary core process for ensuring electromagnetic performance. Production begins with high-quality pig iron and scrap steel as raw materials. Impurities are removed via rough smelting in a converter or electric arc furnace, followed by precise adjustment of alloying elements-such as silicon, manganese, and carbon-in a refining furnace. Silicon content is strictly maintained within the standard range, while harmful impurities like sulfur, phosphorus, and carbon are minimized to prevent adverse effects on magnetic permeability and iron loss. The refined molten steel is cast into billets, reheated to high temperatures, and fed into a hot-rolling mill. Through multiple passes of continuous rolling, the thick billets are transformed into hot-rolled strips of uniform thickness, a process that effectively refines internal grains and densifies the microstructure. Post-rolling, the strips undergo cooling, coiling, and leveling to eliminate rolling stresses, resulting in a hot-rolled silicon steel substrate with stable properties-laying a solid foundation for subsequent cold-rolling and finishing.
Precision cold rolling and annealing are critical processes for shaping silicon steel and optimizing its electromagnetic performance; they are the key technological steps that distinguish high-end electrical silicon steel from ordinary steel. The hot-rolled substrate first undergoes pickling to thoroughly remove surface scale and rust, ensuring a clean surface. It then enters a high-precision cold-rolling mill for multi-pass reduction, where it is rolled to standard ultra-thin specifications-such as 0.1 mm, 0.27 mm, 0.35 mm, or 0.5 mm-based on product requirements. Thickness tolerances and surface flatness are strictly controlled to meet the demands of subsequent precision processing. After cold rolling, the steel retains significant processing stress and suffers from severe grain deformation; characterized by high hardness and brittleness, it cannot be used directly and must undergo high-temperature annealing. Non-oriented silicon steel utilizes a standard continuous annealing process to uniformly refine grain size, ensuring balanced magnetic properties across all directions. In contrast, grain-oriented silicon steel undergoes multi-stage high-temperature annealing and secondary recrystallization processes; these force the grains into an orderly alignment along the rolling direction, achieving unidirectional ultra-low core loss and ultra-high magnetic permeability, thereby fully unlocking the material's superior electromagnetic performance.
Subsequent processes-including coating, finishing/slitting, and final inspection-determine the silicon steel's operational safety, processing compatibility, and ultimate quality. Following annealing, the steel strip undergoes surface cleaning to remove oil and oxide residues; a specialized inorganic insulating coating is then applied uniformly via roller coating and cured at high temperatures. This creates a protective layer characterized by strong adhesion, heat and wear resistance, and excellent insulation, effectively preventing eddy current short circuits between laminations. After coating and curing, the strip undergoes leveling and straightening to correct defects such as warping or waviness, ensuring a flat, uniform surface. Finally, the material is processed-via slitting, cut-to-length shearing, and coiling-into standard silicon steel coils or sheets according to customer specifications. All finished products undergo dimensional re-inspection, surface quality checks, electromagnetic performance sampling, and mechanical property testing; only after meeting all standards are they packaged and warehoused. This comprehensive quality control ensures the finished products meet the manufacturing and operational requirements for various motors, transformers, and precision electrical equipment.
