The use of silicon steel

1. Core application areas
The soft magnetic properties of silicon steel make it the core material for electromagnetic conversion in the fields of electricity, electronics, and home appliances. It is mainly used to manufacture electromagnetic devices such as transformers, motors, reactors, and relays. Specific applications include:
1. Power industry
Power transformer:
The iron core of large power transformers used in power plants and substations requires silicon steel to have low iron loss (reducing power loss) and high magnetic induction intensity to improve transformer efficiency and reduce heat generation.
Distribution transformer:
The iron core material of low-voltage distribution transformers in urban power grids must take into account low loss and economy.
2. Home appliances and consumer electronics
Air conditioning compressor motor:
The iron core of the variable frequency air conditioning compressor uses high-grade silicon steel (such as high-grade cold-rolled non-oriented silicon steel), which requires low loss and high saturation magnetic induction intensity at high frequency to improve energy efficiency.
Refrigerator compressor motor:
Low-noise, high-efficiency compressors require silicon steel with low hysteresis loss and good processing performance.
Microwave oven transformer:
Small high-frequency transformer iron core requires silicon steel to maintain low loss under high-frequency conditions.
3. Industrial motors and drive equipment
Industrial motors:
Stator and rotor cores of asynchronous motors and synchronous motors use non-oriented silicon steel, which requires high magnetic permeability and low loss to improve motor efficiency (such as IE3/IE4 energy efficiency standard motors).
Servo motors and precision drives:
Servo motors of precision equipment such as CNC machine tools and robots require silicon steel to maintain low loss and high response speed at high frequencies.
4. New energy and energy-saving fields
New energy vehicle drive motors:
The cores of electric vehicle drive motors (such as permanent magnet synchronous motors) use high-grade non-oriented silicon steel, which requires low loss, high saturation magnetic density and resistance to high-frequency alternating magnetic fields to improve endurance and power performance.
Wind turbines:
The generator cores of large wind power equipment require silicon steel with high strength and low loss to adapt to long-term outdoor operation.
Energy-saving transformers (amorphous alloy replacement scenarios):
In some scenarios, silicon steel competes with amorphous alloys, and silicon steel has more advantages in overload resistance and processing costs.
5. Special Uses
Military and Aerospace:
Special transformers and sensor cores in radar and navigation equipment require silicon steel to maintain stable magnetic properties in extreme environments (such as high temperature and strong radiation).
High-frequency electronic devices:
For example, the cores of switching power supplies (SMPS) and inverters use thin silicon steel (such as thickness below 0.15mm) to reduce high-frequency losses.
II. Classification and characteristics of silicon steel
According to the production process and magnetic properties, silicon steel is mainly divided into two categories: non-oriented silicon steel and oriented silicon steel. The differences are as follows:
1. Non-oriented silicon steel
Features:
The grain orientation in the silicon steel sheet is randomly distributed, and the magnetic properties are uniform in all directions. It is mainly used in scenes with alternating magnetic fields and variable magnetic field directions (such as motor cores).
Grade naming:
Usually expressed as "W" (non-oriented) + iron loss value + thickness, for example:
35W250: thickness 0.35mm, iron loss value 2.5W/kg (measured at 50Hz, 1.5T).
Low grades (high iron loss) are used for ordinary motors, and high grades (low iron loss) are used for high-efficiency and energy-saving motors.
Typical applications:
Stator/rotor cores of various motors and generators, such as industrial motors, household appliance compressors, and new energy vehicle drive motors.
2. Oriented silicon steel
Features:
Through a special process, the grains are arranged in an orderly manner along the rolling direction (i.e. the length direction of the silicon steel sheet), and the magnetic permeability along the rolling direction is extremely high and the iron loss is extremely low, but the performance in the vertical direction is poor. It is mainly used in unidirectional strong magnetic field scenarios (such as transformer cores).
Subdivision type:
Ordinary oriented silicon steel (GO):
Used for industrial frequency (50/60Hz) transformers, such as distribution transformers, with grades such as 30Q120 (thickness 0.30mm, iron loss 1.2W/kg, measured at 50Hz, 1.7T).
High-grade oriented silicon steel (HiB steel, i.e. high magnetic induction oriented silicon steel):
Higher magnetic permeability and lower iron loss, used in large power transformers (such as 500kV and above ultra-high voltage transformers), grades such as 23ZH105 (thickness 0.23mm, iron loss 1.05W/kg, measured at 400Hz, 1.7T).
Typical applications:
Cores of power transformers, mutual inductors, and reactors, such as large generator transformers and high-speed rail traction transformers.
III. Key performance indicators
The performance of silicon steel directly affects the energy efficiency and reliability of equipment. The core indicators include:
Iron loss (P):
Energy loss (W/kg) generated by unit weight of silicon steel in an alternating magnetic field. The lower the better, which determines the heat generation and energy efficiency of the equipment.
Low-frequency (50/60Hz) scenarios focus on P1.5/50 (iron loss at 1.5T and 50Hz);
High-frequency scenarios (such as new energy vehicles) focus on P1.7/400 (iron loss at 1.7T and 400Hz).
Magnetic induction intensity (Bs):
The higher the saturation magnetic induction intensity, the more compact the core design can be (such as reducing the number of turns), and the higher the power density.
Stacking factor (SF):
The proportion of effective magnetic conductive area after silicon steel sheets are stacked. The higher the magnetic circuit efficiency (the ideal value is close to 1).
Thickness:
The thinner the thickness, the lower the high-frequency loss, but the higher the processing cost. Common thicknesses: 0.15mm, 0.23mm, 0.30mm, 0.35mm.
IV. Key points of production process
The production process of silicon steel is complex, and the composition and organization need to be precisely controlled:
Smelting:
Electric furnace or converter smelting is used to strictly control the silicon content (to avoid segregation), impurities (such as carbon, sulfur, nitrogen) and alloy elements (such as aluminum and manganese).
Rolling:
Hot rolling: Made into thick plates (such as 2-3mm), used for low-grade non-oriented silicon steel.
Cold rolling: Made into thin plates (such as 0.15-0.65mm) through multiple cold rolling. Oriented silicon steel requires specific cold rolling processes (such as decarburization annealing and secondary recrystallization) to make the grains grow in a directional manner.
Annealing:
Decarburization annealing: Reduce the carbon content (<0.003%) to avoid carbides affecting the magnetic properties.
High temperature annealing: Promote grain growth and reduce grain boundary loss (oriented silicon steel needs to form a Gaussian texture).
Coating:
The surface is coated with an insulating layer (such as MgO, phosphate) to reduce inter-sheet eddy current loss and provide rust protection.
V. Industry Development Trends
High efficiency and energy saving:
The global energy efficiency standard upgrade (such as EU IE4, China GB 18613-2020) promotes the growth of demand for high-grade silicon steel (such as 50W350, 35W250).
Thin gauge and high frequency:
High frequency scenarios such as new energy vehicles and renewable energy promote the development of thin gauge silicon steel (such as below 0.15mm) technology.
Low loss and low pollution:
Develop low temperature annealing process and chromium-free coating technology for non-oriented silicon steel to reduce energy consumption and environmental load.
Competition of alternative materials:
Amorphous alloys (lower iron loss) partially replace oriented silicon steel in the field of distribution transformers, but silicon steel still has advantages in mechanical strength and processing cost.