Non-oriented Silicon Steel

Non-oriented silicon steel, also called non-oriented electrical steel, is a soft magnetic alloy primarily composed of iron, silicon, and trace alloying elements. It is a critical core material for manufacturing electrical equipment, characterized by uniform magnetic properties in all directions of the steel sheet plane. This material is widely used in rotating electrical machines and power transformers due to its low iron loss and high magnetic permeability.

Core Composition and Manufacturing Principles

Chemical Composition

Silicon (Si): The key alloying element, typically with a content of 0.5%–3.5%. Adding silicon can increase electrical resistivity, reduce eddy current loss, and improve magnetic permeability. However, excessive silicon will reduce the steel’s ductility and machinability.

Iron (Fe): The base element, ensuring the basic magnetic properties of the alloy.

Trace elements: Strictly control the content of impurities such as carbon (C), sulfur (S), and phosphorus (P). Carbon will increase hysteresis loss, while sulfur and phosphorus can cause embrittlement of the steel sheet.

Optional elements: A small amount of aluminum (Al) can be added to refine grains and further reduce iron loss.

Manufacturing Process FeaturesThe production of non-oriented silicon steel requires precise control of rolling and annealing processes:

Cold rolling: Achieves the required thickness of the steel sheet (usually 0.35 mm or 0.50 mm) and refines the grain structure.

Decarburization annealing: Removes carbon from the steel to reduce hysteresis loss.

Insulating coating: Coats the surface of the steel sheet with a thin insulating layer to prevent eddy current loss between laminations when assembling the core.

Key Performance Indicators

Iron Loss (P₁₀/₅₀, P₁₅/₅₀)The energy loss of the steel sheet in an alternating magnetic field, which is the core indicator for evaluating energy efficiency. It is divided into hysteresis loss (caused by magnetic domain reversal) and eddy current loss (caused by induced current in the steel sheet). Lower iron loss means higher energy efficiency of electrical equipment.

Magnetic PermeabilityReflects the ability of the steel to be magnetized. Higher magnetic permeability enables electrical equipment to reach the rated magnetic flux under lower excitation current, reducing no-load loss.

Magnetic Induction Intensity (B₅₀, B₁₀₀)The magnetic flux density under a specified magnetic field strength. Higher magnetic induction intensity allows the core to be designed more compactly, reducing the volume and weight of electrical equipment.

Ductility and PunchabilityGood ductility ensures the steel sheet can be punched into complex core shapes (e.g., motor stator and rotor cores) without cracking.

Classification and Typical Applications

Non-oriented silicon steel is mainly classified by thickness and iron loss level, with the following typical application scenarios:

Development Trends

Ultra-low loss and high magnetic induction: Developing grades with lower iron loss and higher magnetic induction to meet the energy efficiency requirements of high-end electrical equipment.

Thin-gauge and wide-width: Producing thinner (e.g., 0.20 mm) and wider steel sheets to reduce core loss and improve production efficiency of large-scale equipment.

Specialization for new energy vehicles: Customizing non-oriented silicon steel for drive motors of electric vehicles, which requires a balance of high magnetic properties and high-temperature resistance.

Green manufacturing: Reducing carbon emissions in the production process, developing recyclable silicon steel products to align with environmental protection policies.