How to Produce a Premium No.4 Finish on Hot Rolled Stainless Steel Plates

The Complete Guide to Industrial No.4 Grinding

Among all industrial stainless steel surface finishes, No.4 Finish remains one of the most widely used.

Its uniform, straight grain provides an excellent balance between appearance, functionality, maintenance, and production cost.

While producing a No.4 finish on cold rolled sheets is relatively straightforward, achieving the same quality on hot rolled heavy plates is a much greater engineering challenge.

Hot rolled plates contain:

• Mill scale

• Surface waviness

• Oxide layers

• Minor pits

• Rolling defects

All of these must be removed while maintaining flatness and creating a perfectly uniform grain.

At LEBON MACHINERY, we specialize in heavy-duty grinding solutions for stainless steel plates from 5 mm to 100 mm, helping manufacturers achieve premium No.4 finishes with stable quality and high productivity.

What Is a No.4 Finish?

A No.4 finish is a linear brushed surface produced by abrasive belt grinding.

Unlike a mirror finish, it diffuses light rather than reflecting it directly.

A high-quality No.4 surface should feature:

• Straight and uniform grain

• Consistent color

• No vibration marks

• No chatter marks

• No scratches

• No blind polishing areas

The finish is widely used because it combines attractive appearance with excellent durability and easy maintenance.

Why Is Hot Rolled Stainless Steel More Difficult?

Unlike decorative stainless steel sheets, hot rolled plates are manufactured for structural applications.

Their surfaces are much rougher before grinding.

Typical challenges include:

Black Oxide Scale

The thick oxide layer must be completely removed.

Surface Flatness

Large plates often contain slight deformation after rolling.

Grinding pressure must remain consistent across the entire width.

Surface Defects

Minor pits and rolling marks become more visible after brushing if not removed during rough grinding.

Material Thickness

Thicker plates require:

• Higher grinding force

• Stronger machine structure

• Larger contact rollers

• Stable feeding systems

Without sufficient rigidity, vibration marks quickly appear.

Step 1

Surface Inspection

Before grinding begins, every plate should be inspected.

Engineers should identify:

• Oxide scale

• Weld marks

• Surface pits

• Scratches

• Edge defects

Some localized defects may require manual preparation before entering the production line.

Step 2

Rough Grinding

The first grinding stage removes:

• Oxide scale

• Surface irregularities

• Rolling marks

Heavy stock removal creates a uniform base for the following grinding process.

Choosing the correct abrasive grit depends on:

• Material grade

• Plate thickness

• Initial surface condition

Step 3

Intermediate Grinding

Intermediate grinding reduces the roughness created during the previous stage.

Each grinding pass should remove the scratches produced by the earlier abrasive belt.

Stable pressure and feed speed are essential.

If pressure varies, grain consistency will be affected.

Step 4

Final No.4 Brushing

This stage determines the final appearance.

A premium No.4 finish should show:

✓ Straight grain

✓ Uniform texture

✓ Consistent color

✓ No vibration marks

✓ Excellent visual consistency

This is where machine precision becomes critical.

Why Constant Pressure Matters

Grinding pressure directly influences:

• Surface roughness

• Grain consistency

• Abrasive belt life

• Production efficiency

Too much pressure causes:

• Belt wear

• Overheating

• Surface burning

Too little pressure leaves:

• Uneven grain

• Poor cutting

• Inconsistent appearance

LEBON's constant-pressure grinding technology helps maintain stable contact throughout the polishing process.

Choosing the Right Abrasive Belt

Different abrasive belts produce different textures.

Factors include:

• Grit size

• Belt hardness

• Abrasive material

• Grinding speed

Typical industrial production may use multiple grinding stages before the final No.4 belt.

Proper abrasive selection improves:

• Surface quality

• Belt life

• Production cost

Machine Structure Matters

High-quality No.4 finishes cannot rely on abrasives alone.

The machine itself must provide:

High-Rigidity Frame

To reduce vibration.

Dynamically Balanced Rollers

To eliminate chatter marks.

Precision Belt Tracking

To ensure stable abrasive movement.

Servo-Controlled Pressure

For consistent grinding quality.

PLC Automation

To improve repeatability and production efficiency.

Industries Using No.4 Heavy Plate Finishes

Premium No.4 finishes are widely used in:

Chemical Equipment

Mixing tanks

Pressure vessels

Heat exchangers

Food Processing

Processing equipment

Storage tanks

Sanitary systems

Elevator Manufacturing

Decorative stainless steel panels

Door frames

Interior components

Architectural Decoration

Building facades

Interior wall panels

Public facilities

Kitchen Equipment

Commercial kitchens

Food preparation equipment

Restaurant equipment

LEBON MACHINERY Advantages

Producing a premium No.4 finish requires more than a polishing machine.

LEBON combines:

• Equipment manufacturing

• Real production facilities

• Heavy plate grinding experience

• Continuous process optimization

Our own grinding lines allow us to verify machine performance under real production conditions before delivery.

This practical experience helps customers achieve:

• Higher efficiency

• Better surface consistency

• Lower operating costs

• Longer abrasive life

Frequently Asked Questions

What is the difference between No.4 and Hairline?

No.4 has a shorter, finer grain with a softer appearance.

Hairline finishes feature longer continuous lines and are mainly used for decorative applications.

Can hot rolled plates achieve decorative-quality No.4 finishes?

Yes.

With proper grinding technology and stable equipment, heavy plates can achieve premium industrial and decorative No.4 surfaces.

What causes vibration marks?

Common causes include:

• Poor machine rigidity

• Unbalanced rollers

• Incorrect grinding pressure

• Worn abrasive belts

Why choose LEBON MACHINERY?

LEBON specializes in heavy plate grinding and polishing solutions backed by real production experience.

Our machines are continuously optimized through practical manufacturing rather than laboratory testing alone.

Conclusion

Producing a premium No.4 finish on hot rolled stainless steel plates requires the perfect combination of material preparation, abrasive selection, machine rigidity, constant pressure control, and production experience.

At LEBON MACHINERY, we help manufacturers around the world achieve consistent, high-quality No.4 finishes through advanced grinding technology and practical process expertise.

Whether your application is chemical processing, food equipment, architecture, or industrial manufacturing, LEBON provides reliable solutions designed for long-term performance.

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Looking for a Heavy Plate No.4 Grinding Solution?

Contact LEBON MACHINERY to discuss your material grade, plate thickness, surface finish requirements, and production capacity. Our engineering team will recommend the most suitable No.4 grinding and brushing solution for your project.