About Electrical Steel

In ultra-high voltage (UHV) substations, the lamination thickness of electrical steel sheets is precisely controlled between 0.23 mm and 0.35 mm, equivalent to the thickness of 5 A4 sheets. The (110)[001] texture formed through a special rolling process enables a magnetic flux density of over 1.9 Tesla (T), meaning it can carry a larger magnetic flux at the same volume. It is this precise control of the microstructure that supports over 98% power transmission efficiency of the power grid.

The production of electrical steel is regarded as the "crown jewel" of the metallurgical industry, involving 18 key processes such as steelmaking, hot rolling, normalizing, and cold rolling. Among these, the decarburization annealing process requires maintaining the steel in a hydrogen-nitrogen mixed atmosphere at 800°C for 5 minutes to control the carbon content below 30 parts per million (ppm). For the more precise HiB steel (high magnetic flux density grain-oriented electrical steel), laser scribing is an additional step-creating micron-level grooves on the surface to reduce the magnetic domain width to less than 2 mm.

The shape control in the cold rolling process is nothing short of an art: a six-high rolling mill needs to reduce the thickness of a 3 mm hot-rolled sheet to 0.3 mm, with a thickness deviation of no more than ±3 micrometers (μm). The continuous decarburization annealing line, which uses electromagnetic induction heating, heats the steel strip uniformly to 830°C at a speed of 20 meters per minute (m/min) to form a perfect secondary recrystallization structure. The stable control of this process directly determines the magnetic performance grade of the final product.

Electrical Silicon Steel in new energy

In the new energy vehicle (NEV) sector, the demand for electrical steel is experiencing explosive growth. Non-oriented electrical steel used in drive motors requires a magnetic flux density (B50) of over 1.7 T and an iron loss (P1.5/50) of less than 4.0 watts per kilogram (W/kg). In the permanent magnet synchronous motor of the Tesla Model 3, the stator core is made by laminating 0.25 mm ultra-thin electrical steel sheets-boosting the motor efficiency to over 97% and increasing the driving range by 8%.

The upgrading of wind power equipment further highlights the value of electrical steel. The doubly-fed generators of 5-megawatt (MW) offshore wind turbines require high-grade electrical steel sheets with a thickness of 0.2 mm, and their magnetostriction coefficient must be controlled below 3 ppm to ensure stable operation under strong wind loads. For the latest 10 MW wind turbines developed by China Three Gorges Corporation, optimizing the lamination process of electrical steel sheets has reduced the generator weight by 15% and increased annual power generation by 12 million kilowatt-hours (kWh).