Electrical Steel Sheet

Updated: 2026-07-25

Overview

Electrical steel sheet is a ferromagnetic alloy specifically engineered for efficient energy conversion in electromagnetic devices. Developed in the early 20th century, it revolutionized electrical power systems by dramatically reducing energy losses compared to conventional steel. The material's unique properties stem from silicon additions (typically 1-3.5%) which increase electrical resistivity while maintaining desirable magnetic characteristics. Manufacturers produce two main types: grain-oriented (GO) for directional magnetic fields in transformers and non-oriented (NO) for rotating applications like motors.

Structure and Working Principle

The microstructure of electrical steel contains carefully controlled grain structures that align magnetic domains. In grain-oriented varieties, over 90% of grains align in the rolling direction through complex thermomechanical processing. When subjected to alternating magnetic fields, the material's high permeability allows efficient flux transfer while its laminated construction minimizes eddy current losses. The silicon content raises resistivity approximately fivefold compared to pure iron, significantly reducing wasteful heating effects during operation.

Key Features

Modern electrical steel sheets achieve core losses as low as 0.9 W/kg at 1.5T/50Hz for premium grades. Surface insulation coatings (typically phosphate-based) provide interlaminar resistance while allowing heat dissipation. Grain-oriented versions exhibit magnetic flux density (B8) up to 1.94T, with permeability ratios exceeding 1,800. Manufacturers offer various thicknesses (0.23mm, 0.27mm, 0.30mm, 0.35mm being common) to balance between loss reduction and mechanical strength requirements.

Application Areas

Approximately 75% of electrical steel production serves power transformers, where GO steel's directional properties maximize efficiency. Distribution transformers typically use 0.23-0.27mm thick M4-M6 grade material. Non-oriented grades dominate motor applications, particularly in EVs where high-speed operation demands thin (0.25-0.35mm) high-silicon content sheets. Emerging applications include high-frequency inductors for power electronics, requiring specialized thin-gauge varieties with superior high-frequency characteristics.

Maintenance and Precautions

Proper handling prevents degradation of electrical steel's magnetic properties. Avoid bending beyond minimum radii (typically 5x material thickness) to prevent grain structure damage that increases core loss. Storage should maintain relative humidity below 70% to prevent coating deterioration. During fabrication, use non-contact cutting methods like laser or waterjet when possible, as mechanical punching can create stress-affected zones that impair magnetic performance by up to 15%.

B2B Procurement Guide

Industrial buyers should specify parameters including: core loss grade (e.g., 35W250), thickness tolerance (typically ±0.02mm), coating type (C3 for general purpose, C5 for high corrosion resistance), and magnetic polarization (1.7T minimum for most power applications). Leading global suppliers include Nippon Steel, POSCO, and ThyssenKrupp. Consider minimum order quantities (often 5+ metric tons) and lead times (4-12 weeks for custom grades). Third-party testing for Epstein frame measurements verifies core loss specifications before large purchases.