CRGO electrical steel (Cold Rolled Grain Oriented silicon steel) is a specialized electrical steel used primarily in transformer cores. Its crystal grains are aligned in a single direction during manufacturing, allowing magnetic flux to flow more efficiently through the material. This reduces energy loss and improves transformer efficiency, making CRGO steel the preferred core material for power and distribution transformers worldwide.

Table of Contents

• Introduction to Transformer Core Materials
• What Is Grain Oriented Silicon Steel
• Why CRGO Steel Is Essential for Transformers
• Key Magnetic Properties of CRGO Steel
• Typical CRGO Grades Used in Transformers
• Thickness and Dimensional Characteristics
• Manufacturing Process of CRGO Steel
• Transformer Core Lamination Production
• Global Supply Chain for CRGO Steel
• Industry Standards and Testing Methods
• Market Demand and Energy Infrastructure Trends
• Key Takeaways

Introduction to Transformer Core Materials

Transformers are essential components in modern electrical systems. They enable efficient transmission and distribution of electrical power across long distances and different voltage levels.

At the heart of every transformer lies the transformer core, which acts as the magnetic pathway for transferring energy between windings.

The performance of a transformer core is largely determined by the material used to construct it. An ideal core material should possess several characteristics:

• High magnetic permeability
• Low hysteresis loss
• Minimal eddy current loss
• Stable magnetic performance over time

Electrical steel has been developed specifically to meet these requirements.

Among different electrical steel types, grain oriented electrical steel (CRGO) has become the dominant material used in transformer cores.

Because power transformers operate continuously for decades, even small improvements in magnetic efficiency can result in significant energy savings across power networks.

What Is Grain Oriented Silicon Steel

Grain oriented silicon steel is a type of electrical steel containing approximately 3% silicon, which improves magnetic performance and reduces electrical losses.

The defining feature of this material is its grain orientation.

During manufacturing, the crystal grains within the steel are aligned in a specific direction through controlled rolling and heat treatment processes. This alignment enhances magnetic permeability along the rolling direction.

As a result, magnetic flux can travel more easily through the material when it is oriented properly within a transformer core.

This directional property provides several advantages:

• Reduced core loss
• Higher magnetic permeability
• Improved transformer efficiency
• Lower operating temperatures

Because transformer cores follow a predictable magnetic path, grain oriented steel provides significant efficiency improvements compared with non-oriented steel.

Why CRGO Steel Is Essential for Transformers

Transformers rely on alternating magnetic fields to transfer electrical energy between circuits.

The transformer core must guide magnetic flux between primary and secondary windings as efficiently as possible.

If the core material has high magnetic resistance or high losses, the transformer will waste energy as heat.

CRGO steel solves this problem by combining two key characteristics:

1. Low core loss

2. High magnetic flux density

Low core loss reduces the amount of energy dissipated during each magnetization cycle.

High magnetic flux density allows the transformer to operate efficiently under high magnetic loading conditions.

These properties are particularly important for:

• Power transmission transformers
• Distribution transformers
• Renewable energy transformers
• Industrial transformers

In large power grids, transformer efficiency improvements can translate into substantial reductions in overall energy losses.

For this reason, electrical steel selection is one of the most important factors in transformer design.

Key Magnetic Properties of CRGO Steel

CRGO steel performance is typically evaluated using several standardized parameters.

These measurements are widely used in electrical engineering and transformer manufacturing.

Core Loss (P1.7/50)

Core loss represents the power loss that occurs when the steel is subjected to an alternating magnetic field.

The commonly used measurement P1.7/50 indicates:

magnetic flux density: 1.7 Tesla
frequency: 50 Hz

The unit is watts per kilogram (W/kg).

Lower values indicate better magnetic performance and lower energy loss.

Magnetic Flux Density (B8)

Magnetic flux density measures the ability of the steel to carry magnetic flux under a given magnetizing force.

Higher B values indicate stronger magnetic capability.

Typical B8 values for CRGO electrical steel range from:

1.85 Tesla to 1.89 Tesla.

Thickness

Electrical steel thickness affects eddy current losses.

Thinner materials reduce eddy current losses but may increase manufacturing cost.

Common thicknesses include:

0.18 mm
0.20 mm
0.23 mm
0.27 mm
0.30 mm

Among these, 0.23 mm and 0.27 mm are widely used in transformer core laminations.

Typical CRGO Grades Used in Transformers

Electrical steel grades are typically defined based on their thickness and maximum core loss values.

Below are examples of commonly used CRGO grades.

Grade	Thickness	Core Loss P1.7/50	Magnetic Flux Density
23Q85	0.23 mm	0.80 – 0.85 W/kg	1.85 – 1.89 T
23Q90	0.23 mm	0.85 – 0.90 W/kg	1.85 – 1.89 T
23Q95	0.23 mm	0.89 – 0.91 W/kg	1.85 – 1.89 T
23Q100	0.23 mm	0.90 – 0.97 W/kg	1.85 – 1.89 T
27Q120	0.27 mm	1.05 – 1.15 W/kg	1.85 – 1.89 T

These grades are commonly used in both  distribution transformers and power transformers.

Transformer designers choose specific grades depending on efficiency requirements and cost considerations.

Thickness and Dimensional Characteristics

CRGO electrical steel is typically supplied in coil form before being processed into laminations.

Typical coil widths may include:

600 mm
900 mm
1000 mm
1100 mm
1250 mm

Transformer manufacturers usually process coils through:

• slitting
• cutting
• step-lap lamination punching

Precision in thickness, flatness, and coating quality is critical for ensuring stable transformer core assembly.

Manufacturing Process of CRGO Steel

The production of grain oriented electrical steel requires a sophisticated metallurgical process.

The typical manufacturing sequence includes:

Steelmaking with silicon alloying
Hot rolling
Pickling and cleaning
Cold rolling
Decarburization annealing
Secondary recrystallization annealing
Insulation coating application

The secondary recrystallization process is particularly important because it enables the abnormal grain growth required for grain orientation.

Only a limited number of steel mills globally possess the technology required to produce high-quality CRGO steel.

Transformer Core Lamination Production

Before being assembled into transformer cores, CRGO steel coils are processed into laminations.

Typical processing steps include:

coil slitting
strip cutting
core lamination punching
step-lap stacking

The step-lap core design helps reduce magnetic flux leakage and further improves transformer efficiency.

The quality of lamination processing directly affects transformer performance and operational reliability.

Global Supply Chain for CRGO Steel

CRGO electrical steel is a critical material for the global power industry.

The supply chain typically involves several stages:

steel mill production
coil processing and slitting
lamination manufacturing
transformer core assembly

In many cases, suppliers provide value-added services such as:

coil slitting
custom width processing
small-batch material supply
trial production materials

Companies like MOOPEC support transformer manufacturers by providing flexible supply solutions including customized specifications and small-batch electrical steel supply for prototype and production needs.

Such supply flexibility is particularly important for transformer manufacturers managing multiple projects with varying design requirements.

Industry Standards and Testing Methods

CRGO electrical steel is produced according to international electrical steel standards.

Common standards include:

IEC 60404 electrical steel testing standards
ASTM electrical steel specifications
GB/T grain oriented silicon steel standards

These standards define testing procedures for magnetic properties, dimensional tolerances, insulation coatings, and mechanical characteristics.

Standardized testing ensures consistent performance across transformer manufacturing applications.

Market Demand and Energy Infrastructure Trends

The global demand for electrical steel has been increasing steadily.

Several factors are driving this trend:

expansion of renewable energy generation
growth of electric vehicle charging infrastructure
rising electricity consumption from data centers
modernization of power transmission networks

Large-scale AI data centers, in particular, require massive electrical infrastructure including transformers and substations.

As a result, the demand for high-efficiency transformer core materials continues to grow.

Grain oriented electrical steel is expected to remain a critical material supporting modern energy infrastructure.

Key Takeaways

CRGO electrical steel is the primary material used in transformer cores.

Its grain oriented structure allows magnetic flux to flow more efficiently through the material.

Low core loss improves transformer efficiency and reduces energy waste.

Common grades include 23Q85, 23Q90, and 27Q120.

Typical thicknesses used in transformer cores include 0.23 mm and 0.27 mm.

With increasing global electricity demand, CRGO steel remains a key material supporting modern power infrastructure.

FAQ

What is CRGO steel used for?

CRGO steel is mainly used in transformer cores because it allows magnetic flux to pass efficiently while minimizing energy loss.

What does 23Q90 mean in silicon steel?

23Q90 refers to grain oriented electrical steel with a thickness of approximately 0.23 mm and a maximum core loss of around 0.90 W/kg under standardized testing conditions.

Why is CRGO steel used in transformers?

CRGO steel provides high magnetic permeability and low core loss, which improves transformer efficiency and reduces energy loss.

What thickness of CRGO steel is commonly used?

The most common transformer core steel thicknesses are 0.23 mm and 0.27 mm.