Strategic Planning and Future-Proof Bearing Unit Engineering 420 vs. 440 Stainless Steel

Published in: Food processing and pharmaceutical equipment

Stainless Steel 420 vs. 440 Bearing Units: A Comprehensive Comparison

Author Henning Dahl Nielsen

Published on: 16. February 2025

Performance and Durability

When selecting stainless steel bearing units for industrial applications, the choice between 420 and 440 stainless steel plays a crucial role in determining performance, longevity, and resistance to wear and corrosion. Both materials offer unique benefits, making them suitable for different environments, including food processing, pharmaceutical production, and heavy-duty machinery.

This guide will provide a detailed comparison between Stainless Steel 420 and 440 bearing units, examining their properties, applications, advantages, and limitations to help you make an informed decision.

Stainless Steel 420 vs. 440 Bearing Units

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Understanding Stainless Steel 420 and 440

What is Stainless Steel 420?

Stainless Steel 420 is a martensitic stainless steel with a high carbon content that enhances hardness and wear resistance. It is widely used in applications where moderate corrosion resistance and high strength are required.

Key properties of 420 stainless steel:

Hardness: Can be hardened to 50 HRC (Rockwell Hardness).
Corrosion Resistance: Moderate, suitable for mildly corrosive environments.
Strength: Good mechanical strength, but lower than 440 stainless steel.
Composition: Contains 12-14% chromium and up to 0.40% carbon.
Magnetic Properties: Magnetic due to its martensitic structure.

What is Stainless Steel 440?

Stainless Steel 440, particularly 440C, is another martensitic stainless steel with higher carbon content, making it harder and more wear-resistant than 420 stainless steel. It is often used in extreme wear applications.

Key properties of 440 stainless steel:

Hardness: Can be hardened to 58-60 HRC, making it one of the hardest stainless steels available.
Corrosion Resistance: Higher than 420 stainless steel, but lower than austenitic grades like 316.
Strength: Higher tensile and yield strength compared to 420.
Composition: Contains 16-18% chromium and up to 1.2% carbon.
Magnetic Properties: Also magnetic due to its martensitic structure.

Comparing Stainless Steel 420 vs. 440 in Bearing Units

Property	Stainless Steel 420	Stainless Steel 440
Hardness (HRC)	48-50	58-60
Corrosion Resistance	Moderate	High
Wear Resistance	Moderate	Excellent
Strength	Good	Higher than 420
Magnetic	Yes	Yes
Machinability	Easier to machine	Difficult to machine
Cost	Lower	Higher

Corrosion Resistance Comparison

420 stainless steel has moderate corrosion resistance but is prone to rusting in highly corrosive environments.
440 stainless steel offers better corrosion resistance due to its higher chromium content but is still not as corrosion-resistant as austenitic stainless steels like 304 or 316.

Wear Resistance and Hardness

440 stainless steel is superior in wear resistance, making it suitable for high-load and high-speed applications.
420 stainless steel is softer, meaning it wears faster under heavy loads.

Machinability and Workability

420 stainless steel is easier to machine, making it more cost-effective for manufacturing bearing units.
440 stainless steel is harder to machine due to its higher hardness.

Cost and Availability

420 stainless steel is more affordable, making it ideal for budget-sensitive applications.
440 stainless steel is more expensive but offers higher durability.

Applications of Stainless Steel 420 vs. 440 Bearing Units

Best Applications for 420 Stainless Steel Bearing Units

Food processing equipment (mild environments)
Light-duty conveyors
General industrial machinery
Low-moisture environments
Medical equipment
Automotive applications (moderate stress)

Best Applications for 440 Stainless Steel Bearing Units

Pharmaceutical processing
High-speed machinery
Heavy-duty industrial applications
Harsh environmental conditions (high humidity, mild chemicals)
Precision instruments
Aerospace and defense applications

Which Stainless Steel Bearing Unit Should You Choose?

Choose 420 Stainless Steel If:

✔ You need a more cost-effective solution.
✔ The application involves moderate corrosion conditions.
✔ You require easier machinability.
✔ You need a balance between strength and affordability.

Choose 440 Stainless Steel If:

✔ You need high wear resistance for heavy loads.
✔ The environment involves higher humidity and mild chemicals.
✔ You require superior hardness and durability.
✔ You are using bearings in high-speed applications.

Balancing Performance and Cost

Both Stainless Steel 420 and 440 bearing units serve important roles in industrial applications. The decision between these two materials comes down to balancing performance, cost, and environmental conditions.

For general industrial applications where moderate corrosion resistance and good strength are required, 420 stainless steel is a solid choice.
For high-performance applications that demand superior hardness and wear resistance, 440 stainless steel is the better option.

By understanding the key differences and selecting the right material, you can improve machine efficiency, reduce maintenance costs, and enhance long-term reliability.