Overview of Electrical Steel

Introduction

Electrical steel, also known as silicon steel, is an alloy of carbon, silicon, and iron. It contains 0.5% to 4.5% silicon. The magnetic permeability of iron is greatly enhanced by adding silicon, which improves the efficiency of electric energy generation, transmission, and use. Electrical steel, therefore, has high magnetic permeability, low coercive force, and high resistivity, making it ideal for use in power, electronics, aerospace, and military industries.

Classification of Electrical Steel

Electrical steel is classified based on production processes and grain orientation:

Production Processes:
- Hot-Rolled Electrical Steel: Largely replaced by cold-rolled electrical steel due to technological advancements.
- Cold-Rolled Electrical Steel: Preferred for its superior properties and divided into non-oriented and oriented types.
Grain Orientation:
- Oriented Electrical Steel: Grains are aligned in the rolling direction, offering excellent magnetic induction strength. Ideal for stationary devices like transformers.
- Non-Oriented Electrical Steel: Grains are randomly oriented, providing good magnetic induction in all directions. Suitable for rotating devices like industrial motors, new energy vehicle motors, and household appliance motors.

Oriented electrical steel is further classified based on magnetic induction intensity:

General Oriented Electrical Steel (CGO): Magnetic induction intensity < 1.88T.
High Magnetic Induction Oriented Electrical Steel (Hi-B): Magnetic induction intensity ≥ 1.88T, with lower iron loss performance.

Non-oriented electrical steel is categorized by iron loss performance:

High-Grade Non-Oriented Electrical Steel: Iron loss P1.5/50 ≤ 4.00W/kg.
Medium- and Low-Grade Non-Oriented Electrical Steel: Higher iron loss than high-grade.

Performance Characteristics

The production of electrical steel, especially oriented types, involves complex processes and equipment with stringent composition control. The quality of oriented electrical steel is a key indicator of a country’s special steel manufacturing technology.

Key performance requirements:

Core Loss: Indicates energy efficiency.
Magnetic Induction Intensity: Indicates magnetic performance.

Other characteristics:

Long Production Process: Includes smelting, rolling, decarburization annealing, high-temperature annealing, hot stretching, flattening, and laser scoring.
Numerous Key Process Control Points: Over 600 control points must meet standards for product qualification.
High Process Control Accuracy: Precise control, such as maintaining molten steel composition within ±7ppm, is crucial.
Long Product Certification Cycle: For example, high-grade non-oriented electrical steel for the automotive industry can take 6 to 10 years from production line setup to product certification.