Electrical steel —often called lamination steel in industry—is the magnetic material used in most motors, transformers, and generators. Grade selection affects everything from core loss and heat generation to machine size, particularly in higher-frequency designs.

Main Elements to Remember

Electrical steel is special steel for magnetic uses, like motors and transformers.
Grades split into two main types: Grain-Oriented (GOES) for transformers and Non-Oriented (NGOES) for motors.
Modern grade names (like M270-50A) show core loss, thickness, and type. This makes picking easier.
Lower core loss usually means better efficiency and less heat, but the material cost goes up pretty quickly as performance improves.
Picking the right grade means balancing what you need (frequency, efficiency) with your budget.

The Two Key Types: GOES vs. NGOES

The first step to choosing electrical steel grades is to know the two main types which are Grain-Oriented Electrical Steel (GOES) and Non-Oriented Electrical Steel (NGOES). The difference between the two types is the arrangement of their crystals or "grain."

Grain-Oriented (GOES): For Directional Power

In GOES, the grain structure is intentionally aligned with the rolling direction to reduce core loss along the main magnetic path.

Transformer cores almost always rely on GOES because the magnetic flux follows a fairly predictable direction.

Non-Oriented (NGOES): For Rotating Fields

NGOES does not have a preferred grain direction, so it performs well in motors and generators where magnetic flux changes direction continuously during operation.

In practice, you’ll see NGOES everywhere from appliance motors to larger industrial generators. Among many other things, Cold Rolled Motor Lamination (CRML) steels are the least expensive semi-processed materials that are made from NGOES.

Interpreting Electrical Steel Grade Tags

Before comparing grades, it helps to understand the naming system. The naming looks messy at first, but once you know the pattern, most grades become easy to read. Their structure conveys some information about the performance of the given steel.

Recognizing the "Old Guard": AISI/ASTM Designators

Some are even older names for grades, particularly in North America. These are what, "M-grades", or simply "M-grades," such as M-15, M-19, or M-47, are often referred to as.

In older AISI naming systems, lower grade numbers generally indicated lower core loss and better magnetic performance. Thus, it is indeed regarded as a loose name of a grade today. Although still often used, these old AISI trading names are replaced by modern designations that are comprehensible and more precise.

Silicon steel naming rules from HWHG

The grade code is only a starting point; the stated loss value and test conditions should still be checked against the supplier’s electrical steel certificate.

The Modern Standard: European (EN) and IEC Naming Logic

Most manufacturers now use IEC or EN naming systems because they describe core loss, thickness, and material type more directly.

M: This letter indicates that it's a magnetic steel.
235: For example, in M235-35A, “235” refers to a maximum core loss of 2.35 W/kg.
35: “35” indicates a thickness of 0.35 mm.
A: This letter indicates the steel type. "A" is non-oriented. "P" is for conventional grain-oriented. "S" refers to high-permeability grain-oriented.

Naming System Comparison

The newer system is more practical because you can read the key performance data straight from the grade itself. For example, a comparison of an old grade to a new one.

Standard	Example Grade	What it Tells You
AISI (Old)	M-19	A grade with specific core loss limits (you need to look them up).
EN 10106 (New)	M270-50A	M: Magnetic Steel, 270: Max core loss of 2.70 W/kg, 50: 0.50 mm thick, A: Non-oriented.

Key Performance Differences: What the Grades Really Tell You

The grade name points to key performance measures. Understanding these helps you see the real trade-offs between different electrical steel grades.

Core Loss (W/kg): The # 1 Enemy of Efficiency

Core loss directly affects how much energy is converted into heat during operation. Under the relevant standard test conditions, a high-performance grade such as M235-35A may have a specified loss of around 2.35 W/kg, compared with approximately 8.00 W/kg for a standard grade such as M800-65A. That gap can translate into lower winding and core temperatures, improved efficiency, or less demand on the cooling system.

The lowest-loss grade is not automatically the right choice, however. Designers also need to check permeability and the usable flux-density range.

Permeability shows how much magnetizing force is needed to establish flux in the steel. Higher permeability can reduce magnetizing current, particularly when the machine operates below the knee of the magnetization curve.

Flux density indicates how strongly the material is magnetized. Once the steel approaches saturation, additional current produces relatively little additional flux. This is where grade selection becomes critical. A material that performs adequately at moderate flux density may require more current, generate more heat, or limit output when used closer to saturation.

For this reason, grade comparisons should be based on the intended frequency, flux density, lamination thickness, and operating temperature. Magnetization curves and guaranteed values in manufacturer data sheets, such as those supplied by Aperam, provide a more useful basis for selection than the grade designation alone.

The Effect of Thickness and Processing

High-frequency applications such as EV traction motors typically use thinner gauges because lamination thickness affects eddy-current loss, stamping difficulty, and production cost.

In the market, you may also come across "fully processed" and "semi-processed" grades. Fully processed grades are supplied with their magnetic properties already developed at the mill. Semi-processed grades require a final annealing step after stamping to achieve their intended magnetic performance.

The production process of electrical steel at Hongwang factory

The production process of electrical steel at Hongwang factory

A Practical Guide to Electrical Steel Grade Selection

Once the flux path is understood, grade selection usually comes down to balancing frequency, efficiency, manufacturability, and cost.

What Usually Drives Grade Selection

After that, the trade-offs become more application-specific.

In EV traction motors, the main priorities are limiting high-frequency losses and maintaining power density without excessive thermal load. That is why EV traction designs often use thin, high-silicon non-oriented electrical steel, typically in the 0.20–0.35 mm range. Appliance motors typically use standard NGOES grades such as M400-50A, where cost matters more than peak efficiency.

In practice, most selections come down to a few trade-offs:

Operating Frequency: For higher frequencies (like in an EV motor), it is necessary to use thinner steel in order to keep eddy current losses under control.
Efficiency Target: In continuously operating industrial motors, if you need to achieve very high efficiency, then you should select a grade with low core loss, which will be more expensive initially but will save energy in the long run.
Cost Budget: The project budget will always be a significant factor. Electric steel grades with better properties are always more expensive.
Power Density: When a motor needs to be more powerful in a smaller size, then you need a grade with both high permeability and high saturation induction.

Typical Grade Choices by Application

Having gained sufficient knowledge from the first two steps, you can now make the right choice. The following table presents the common applications and the corresponding typical electrical steel grade designation used.

Application	Expected Grade Type	Main Factors
Power Transformer	High-Permeability GOES	The core loss at 50/60 Hz should be minimal.
Electric Vehicle Motor	Thin-Gauge, High-Silicon NGOES	Take note of the core loss at high frequencies, and also of the high strength.
Common Motor	Standard NGOES (e.g., M400-50A)	The performance and costs are adequately distributed.
Electric Jacuzzi Motor	Thicker, Low-Cost NGOES or CRML	The main point is the cost.

Conclusion: The main important points for choosing the proper grade

In real projects, grade selection is rarely about chasing a single “best” material. Most of the time it’s a compromise between efficiency, manufacturability, operating frequency, and budget. Once you get familiar with the naming logic and the main magnetic properties, comparing grades becomes much more straightforward.

Frequently Asked Questions

What is the main difference between M-19 and M-22 electrical steel?

M-19 and M-22 are other names for non-oriented electrical steel which are the older AISI codes. Therefore, it is a more technical choice (and generally more expensive) for applications in which performance is a critical factor.

Does higher silicon content always improve electrical steel?

In practice, more silicon is useful — up to the point where manufacturing starts becoming difficult.

Why is electrical steel always laminated?

Electrical steel is built in such a way that the thin sheets (laminations) are insulated from each other and are used to fight eddy currents. A chunk of steel in an AC magnetic field would develop large, circling eddy currents, causing a lot of energy loss as heat.

Can I use regular carbon steel for a motor core?

Technically yes, but efficiency would be poor compared with electrical steel laminations. Electrical steel is used because its lower magnetic losses improve efficiency and reduce heat generation under alternating magnetic fields.

What does "fully processed" mean for electrical steel grades?

"Fully processed" is the term that implies that the steel has reached its final state in the production process by receiving its final heat treatment, which is called annealing, at the steel mill. This steel, when received, has its specified magnetic properties. Once it is stamped and assembled, it is ready to do so.

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