In today’s modern power systems, transformers play a vital role. Their primary function is to regulate voltage levels, enabling electricity to be efficiently transmitted from power plants to industrial equipment, commercial facilities, and households. A transformer is mainly composed of a core and windings.

Transformer core

Among these, the core is the heart of the transformer, responsible for efficiently guiding the magnetic flux generated in one winding to another, enabling voltage conversion. The performance of the core directly impacts a transformer’s energy efficiency, heat loss, noise level, and service life. The core is made from a critical material known in the industry as transformer steel, also called silicon steel or electrical steel.

Why Is Grain-Oriented Silicon Steel (CRGO) Preferred for Transformer Steel?

Silicon steel is generally categorized into two types: Grain-Oriented (CRGO) and Non-Grain-Oriented (CRNGO). For transformer cores, CRGO is almost exclusively used.

That’s because CRGO has grain structures aligned in the rolling direction, allowing magnetic flux to pass through with minimal resistance. This leads to significantly reduced energy loss and higher electromagnetic efficiency. In contrast, CRNGO has random grain orientation and is more suited for applications requiring uniform magnetic properties in all directions, such as motors.

Advantages of grain-oriented transformer steel:

• High magnetic permeability, improving magnetic transmission efficiency
• Higher core loss , reducing energy and heat waste
• Stable performance for long-term operation
• Highly adaptable for various grades and thicknesses

Key Factors to Consider When Choosing Transformer Steel

If you’re a buyer, these are the most critical aspects to assess when selecting transformer-grade silicon steel:

1. Magnetic Properties – The Core of Efficiency

High permeability ensures magnetic fields pass through with less resistance, improving conversion efficiency and energy savings.

Low coercivity reduces energy loss during magnetization cycles.

Top-performing transformer steels typically exhibit both traits. For example:

27QG110 (China – Baosteel)

23RK80

20RK65

These 0.27/0.23/0.20mm-thick grades deliver excellent magnetic performance, ideal for high-efficiency distribution transformers.

2. Core Loss – A Key Metric for Energy-Efficient Designs

Hysteresis loss results from repeated magnetization cycles. Premium CRGO helps minimize this loss.

Eddy current loss arises from transverse currents within the laminations and can be reduced using thin, coated silicon steel sheets.

Higher core loss materials are crucial for energy-saving transformer designs. Typical grades include:

27Q120 (Baosteel)

23Q85

20RK75

18RK65

30P110 (POSCO)

These 0.18–0.30mm materials are widely used in industrial transformers for minimizing no-load losses.

3. Silicon Content – Balancing Performance and Workability

Most transformer steels contain 2–4% silicon. A higher silicon content improves resistivity and reduces energy loss but also makes the steel more brittle and harder to process.

Higher grades offer a good compromise between performance and punchability.

4. Lamination Thickness – A Double-Edged Sword

Silicon steel typically ranges from 0.18mm to 0.35mm:

Thinner laminations reduce eddy current losses, enhancing performance

However, thinner materials are harder to process and more costly, especially in high-speed stamping

Choose based on your product's positioning and cost-performance expectations.

Common high-efficiency transformer steel grades:

23QG095 (Baosteel)

23QG080

27QH095 (Baosteel)

These 0.20–0.27mm grades are optimal for dry-type and energy-saving distribution transformers.

5. Insulating Coating – A Dual Benefit

High-quality transformer steel comes with specialized coatings that:

Prevent interlaminar current leakage, reducing eddy current loss

Enhance heat and oxidation resistance, prolonging core lifespan

Reduce tooling wear during stamping

Meet environmental standards (low VOC, heavy-metal-free)

Clearly define your coating requirements—standard, high-temperature, or eco-friendly—before ordering.

At MOOPEC, we help clients choose the right materials based on their heat resistance, environmental, and tooling durability needs.

6. Mechanical Properties – Can It Withstand the Process?

Apart from electrical performance, good transformer steel must:

Resist fracture during shearing and punching

Retain flexibility across multiple forming operations

Especially with thinner gauges or high-frequency stamping, superior mechanical durability is essential.

7. Thermal Stability – Ready for Real-World Conditions

Transformers generate heat during operation. Without adequate thermal resistance, steel can degrade over time.

Choose thermally stable grades for high-load or high-temperature environments:

27QH100 (Baosteel)

M103-27P5 (JFE)

27PG110 (POSCO)

Ideal for use in deserts, highlands, or regions with extreme temperature variations.

8. Cost and Budget Control

Material cost: High-grade, low-loss steel costs more but improves energy efficiency and durability—suitable for premium transformers.

Manufacturing cost: Thin or high-grade steel often requires advanced tooling and processes.

Suppliers should match material recommendations with customer budgets through a comprehensive techno-economic analysis.

9. Environmental & Compliance Requirements

More clients now require transformer steel to meet environmental standards:

Free from heavy metals or hazardous substances

Eco-friendly coatings

Support for carbon audits and energy certifications

MOOPEC provides full inspection reports or environmental declarations to support certifications.

10. Supply Chain Stability & Service Capabilities

Long-term partnerships depend on:

Stable material availability

Fast and flexible delivery

Technical support for sampling and customization

Consider whether the supplier:

Supports low-volume, multi-spec sourcing

Offers quick sampling and prototyping

Has localized stock or overseas warehousing for urgent deliveries

A dependable transformer steel supplier should be your partner throughout R&D, production, and after-sales optimization.

Conclusion: A Good Transformer Steel Ensures Efficiency and Reliability

The efficiency, stability, and longevity of a transformer are largely determined by the core material. Grain-oriented silicon steel (CRGO) has become the standard for transformer steel thanks to its superior magnetic properties and low loss performance.

When recommending materials, MOOPEC evaluates all factors—magnetic performance, workability, cost, compliance, and supply continuity—to ensure the best fit for your needs.

Why Choose MOOPEC

MOOPEC has specialized in supplying and processing transformer steel (CRGO/CRNGO) for over 20 years. We understand the strict performance and delivery requirements of transformer manufacturers and offer:

Custom exampling, multi-spec services to support R&D and multi-product production

7-day fast delivery to shorten project timelines

End-to-end quality control from selection, decoiling, slitting, cutting, to packing and shipment

Global service network covering Southeast Asia, Europe, and North America for fast localized response

Expert technical support to assist with material selection, sampling, and feedback across all project stages

If you're looking for a reliable transformer steel partner, we’re here to help.

MOOPEC – Empowering global manufacturing for a smarter, more efficient electrical future.