Electrical Steel Coil (Silicon Steel): Properties, Roll Forming Limits & When It’s Relevant

Electrical steel, commonly called silicon steel, is a specialized alloy engineered for magnetic performance, not structural strength or corrosion resistance.

It is primarily used in:

• Transformer cores

• Motor laminations

• Generators

• Inductors

• Magnetic circuits

• Electrical equipment housings (in specific cases)

Unlike roofing, structural, or façade steels, electrical steel is optimized for:

• Low core loss

• High magnetic permeability

• Controlled grain orientation

• Reduced eddy current losses

For roll forming manufacturers, electrical steel is rarely used in conventional roofing or structural profiles. However, it becomes relevant in niche applications involving:

• Electrical enclosures

• Motor housing components

• Laminated frame channels

• Specialty magnetic structural parts

Understanding when it matters — and when it does not — is critical.

1️⃣ What Is Electrical Steel?

Electrical steel is carbon steel alloyed with silicon (typically 2–3.5%) to improve magnetic performance.

Silicon addition:

• Increases electrical resistivity

• Reduces eddy current loss

• Improves magnetic efficiency

• Reduces hysteresis loss

However:

• Increases brittleness

• Reduces ductility

• Increases forming difficulty

2️⃣ Types of Electrical Steel

2.1 Non-Grain Oriented (NGO)

• Magnetic properties similar in all directions

• Used in motors and rotating machinery

• More common in coil supply

More relevant for roll forming applications.

2.2 Grain Oriented (GO)

• Magnetic properties optimized in rolling direction

• Used in transformer cores

• Typically processed via stamping and stacking

GO material is generally not used in traditional roll forming because directional magnetic properties are critical.

3️⃣ Mechanical Properties

Electrical steel differs significantly from structural steel.

Property	Mild Steel	Electrical Steel
Yield Strength	250 MPa	280–400 MPa
Ductility	Moderate	Reduced
Silicon Content	<0.2%	2–3.5%
Magnetic Properties	Standard	Engineered
Brittleness	Low	Higher

Increased silicon reduces ductility and increases cracking risk during forming.

4️⃣ Forming Behavior in Roll Forming

Electrical steel is more brittle than conventional structural steel.

Key impacts:

• Reduced bend tolerance

• Increased edge cracking risk

• Higher sensitivity to slit edge quality

• Limited minimum bend radius

4.1 Bend Radius Requirements

Due to silicon content:

• Minimum bend radius must be larger than mild steel

• Tight bends increase cracking risk

• Cold forming requires careful strain distribution

Gradual multi-pass forming is essential.

4.2 Springback

Springback behavior depends on grade, but:

• Yield strength is moderate

• Elastic modulus remains ~210 GPa

Springback can be similar to G350 depending on composition.

Tooling compensation may be required.

5️⃣ Thickness & Application Context

Electrical steel is typically supplied in:

• 0.23 mm

• 0.27 mm

• 0.35 mm

• 0.50 mm

Thin gauges are common because laminations reduce eddy current loss.

In roll forming applications (if used for enclosures or channels), thickness may be slightly higher.

6️⃣ Surface Coatings & Insulation Layers

Electrical steel often includes:

• Thin insulating coatings

• Oxide layers

• Phosphate treatments

These coatings:

• Electrically isolate laminations

• Reduce short-circuiting between layers

During roll forming:

• Surface damage may affect magnetic performance

• Excessive roll pressure can damage insulation coating

This is critical for magnetic applications.

7️⃣ Tooling & Machine Considerations

When forming electrical steel:

• Use high-quality slit edges

• Maintain proper strip tension

• Avoid aggressive early forming

• Use polished rolls to protect surface coatings

Silicon content increases brittleness, so crack initiation risk is higher than mild steel.

8️⃣ When Electrical Steel Is Relevant in Roll Forming

Electrical steel becomes relevant in:

• Motor housing channels

• Transformer frame supports

• Magnetic shielding channels

• Electrical panel structural members

• Specialty industrial electrical equipment

It is generally NOT used for:

• Roofing

• Cladding

• Purlins

• Structural framing

• Standard flashing

9️⃣ Magnetic Property Protection During Forming

Over-forming, heavy cold work, or excessive stress can:

• Increase core losses

• Distort magnetic grain structure

• Reduce permeability

Although minor in structural components, this matters in magnetic circuit parts.

Therefore:

• Avoid excessive cold deformation

• Maintain controlled forming strain

• Minimize work hardening in critical zones

🔟 Slitting Quality & Edge Cracking

Electrical steel is highly sensitive to:

• Burr height

• Edge micro-cracks

• Slit-induced stress

Poor slit quality causes:

• Edge splitting

• Flange cracking

• Premature failure

Precision slitting is mandatory.

1️⃣1️⃣ Buyer Strategy (30%)

When Electrical Steel Should Be Specified

• Magnetic performance is critical

• Laminated electrical components

• Motor frame components requiring magnetic efficiency

• Transformer support structures

When It Should Not Be Used

• Structural strength priority

• Corrosion exposure priority

• Cost-sensitive structural profiles

• Outdoor architectural systems

Electrical steel is engineered for magnetic performance — not structural optimization.

Common Buyer Mistakes

1. Assuming electrical steel equals high-strength steel

2. Using for structural applications without corrosion protection

3. Ignoring bend radius limitations

4. Damaging insulation coating during forming

5. Not verifying grain orientation

6. Treating it like mild steel in tooling design

1️⃣2️⃣ Corrosion Considerations

Electrical steel is typically not corrosion-resistant.

If used outdoors:

• Requires coating or painting

• Needs proper surface protection

It is not a substitute for galvanized or stainless materials.

6 Frequently Asked Questions

1. What is silicon steel used for?

It is primarily used for transformers, motors, and magnetic core applications.

2. Is electrical steel stronger than mild steel?

It may have moderate strength but is more brittle due to silicon content.

3. Can electrical steel be roll formed?

Yes, but bend radius and crack control are critical.

4. What is the difference between grain-oriented and non-grain-oriented steel?

Grain-oriented steel has directional magnetic properties; non-grain-oriented does not.

5. Is electrical steel corrosion resistant?

No. It requires coating if used in exposed environments.

6. Is electrical steel relevant for roofing or purlins?

No. It is not designed for structural roofing applications.

Final Engineering Summary

Electrical steel (silicon steel) is a specialized magnetic material optimized for:

• Reduced core losses

• Improved permeability

• Efficient energy transfer

In roll forming, it presents:

• Higher brittleness

• Crack sensitivity

• Surface coating protection challenges

It is relevant only in niche applications involving magnetic components or electrical equipment structures — not general structural or roofing systems.