420 vs AUS 8 Knife Steel Comparison

420 vs. AUS-8 Knife Steels: A Comprehensive Comparison

Below is an updated and enriched comparison of 420 and AUS-8 knife steels, incorporating additional details on 420 variants (like 420HC), real-world usage, popular alternatives, and maintenance tips. Whether you’re exploring bushcraft, everyday carry (EDC), or simply curious about the performance of kitchen knives, this guide should help you make an informed decision.

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TABLE OF CONTENTS

1. Introduction
2. Chemical Composition Overview
   2.1 420 Steel Composition
   2.2 AUS-8 Steel Composition
3. Typical Hardness (Rockwell C) Ranges and Practical Implications
4. Detailed Alloy Element Effects
5. Heat-Treatment Nuances and Forging
6. Performance Characteristics
   6.1 Corrosion Resistance
   6.2 Toughness
   6.3 Edge Retention
   6.4 Ease of Sharpening
7. Patina Formation and Protective Coatings
8. Side-by-Side Comparison (Table)
9. Ideal Uses
10. Pros and Cons
    10.1 420 Steel
    10.2 AUS-8 Steel
11. Conclusion and Key Takeaways

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1. INTRODUCTION

420 and AUS-8 are two popular stainless steels in the knife-making world. Both are relatively affordable, widely available, and well-suited to general-purpose cutting tasks. They each offer balanced tradeoffs between corrosion resistance, toughness, and edge retention, making them suitable for beginners, casual users, and even experienced collectors who want budget-friendly or mid-range options. In this article, we’ll explore their chemical makeup, typical hardness levels, heat-treatment nuances, and real-world performance comparisons to help you decide which steel is best for your needs.

Note on Alternatives
Other steels commonly found in similar price ranges include 8Cr13MoV (often used by Spyderco and Kershaw) and 420HC (used by Buck). These may offer slightly different performance characteristics but share a similar entry-level to mid-range reputation.

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2. CHEMICAL COMPOSITION OVERVIEW

Chemical compositions can vary by manufacturer, but the figures below offer a good baseline.

2.1 420 Steel Composition

• Carbon: ~0.38%
• Chromium: ~13.6%
• Manganese: ~0.5%
• Silicon: ~0.75%
• Sulfur: ~0.03%
• Vanadium: ~0.3%

420 steel is a low-carbon, high-chromium stainless steel. Its chromium content (above 12%) qualifies it as “stainless,” providing excellent corrosion resistance. However, the relatively low carbon content typically leads to a softer steel, which is extremely easy to sharpen.

2.2 AUS-8 Steel Composition

• Carbon: ~0.70–0.75% (commonly ~0.725%)
• Chromium: ~13.0–14.5% (often ~13.75%)
• Manganese: ~0.5%
• Molybdenum: ~0.2%
• Nickel: ~0.49%
• Phosphorus: ~0.04%
• Silicon: ~1.0%
• Sulfur: ~0.03%
• Vanadium: ~0.18%

AUS-8, originally from Japan, belongs to a family that also includes AUS-6 and AUS-10. It has moderately higher carbon than 420, allowing for greater hardness while maintaining good corrosion resistance and decent edge retention.

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3. TYPICAL HARDNESS (ROCKWELL C) RANGES AND PRACTICAL IMPLICATIONS

• 420 Steel: Often heat-treated to around 50–53 HRC (though some manufacturers may push it slightly higher). This relatively soft range makes it easy to sharpen but compromises long-term edge retention.
• AUS-8 Steel: Commonly hardened to around 57–59 HRC. This higher range yields better cutting performance and edge stability compared to 420, though it may require slightly more effort to sharpen.

Practical Implications:

• A lower-HRC steel (like 420) is very forgiving and quick to sharpen, but it won’t hold its edge as long.
• A mid-range HRC steel (like AUS-8) retains an edge better, though sharpening demands a bit more skill or time.

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4. DETAILED ALLOY ELEMENT EFFECTS

• Carbon: Boosts hardness, edge retention, and strength; higher in AUS-8 (~0.725%) vs. 420 (~0.38%).
• Chromium: Essential for stainless properties. Both contain enough (13%+) to provide good corrosion resistance.
• Manganese: Aids in grain refinement and steel hardenability; both have ~0.5%.
• Silicon: Improves strength and oxidation resistance; slightly higher in AUS-8 (~1.0%) than 420 (~0.75%).
• Vanadium: Forms hard carbides for edge stability and wear resistance. Although 420 shows ~0.3% and AUS-8 ~0.18%, AUS-8’s higher carbon content often compensates.
• Molybdenum (AUS-8): Helps refine grain structure and further enhances corrosion resistance.

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5. HEAT-TREATMENT NUANCES AND FORGING

• 420 Steel:

  • Known for its simplicity in heat treatment.
  • Lower carbon content makes it forgiving regarding warping and cracking.
  • Cannot achieve extremely high hardness; manufacturers focus on precise quenching and tempering to optimize its toughness and basic edge performance.

• AUS-8 Steel:

  • Also straightforward to work with, but can reach higher hardness (typically up to ~59 HRC) with good control.
  • Some knifemakers use sub-zero quenching or cryogenic treatments to refine grain structure.
  • Less prone to warping or cracking than many high-carbon steels.

Special Note on 420HC
A variant with slightly higher carbon (~0.45%), 420HC can achieve a higher HRC (mid-50s or slightly more) compared to standard 420. Buck Knives, for instance, is renowned for its well-executed 420HC heat treatment, yielding performance notably above standard 420.

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6. PERFORMANCE CHARACTERISTICS

6.1 Corrosion Resistance

• 420: Very Good
• AUS-8: Very Good

Both are stainless steels, so rust resistance is strong in normal usage. 420 is sometimes employed in marine and medical applications given its high chromium content (relative to carbon), maintaining a corrosion-resistant matrix.

6.2 Toughness

• 420: Good
• AUS-8: Good

Both steels have decent toughness, especially compared to many higher-hardness or high-carbon steels that can be brittle. For typical everyday tasks, they handle impacts reasonably well.

6.3 Edge Retention

• 420: Fair
• AUS-8: Fair/Moderately Good

Neither is known for exceptional wear resistance. They should be fine for light-to-moderate tasks but will require more frequent touch-ups than higher-end steels like S30V or VG-10. AUS-8 generally has a slight advantage over 420, thanks to its higher hardness and carbon content.

6.4 Ease of Sharpening

• 420: Excellent
• AUS-8: Very Good

420’s softer nature allows rapid sharpening with basic stones or even pocket sharpeners. AUS-8, though harder, remains more manageable to sharpen than many premium steels.

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7. PATINA FORMATION AND PROTECTIVE COATINGS

Because both 420 and AUS-8 contain sufficient chromium, they typically do not form a patina as high-carbon, non-stainless steels (like 1095) do. A forced patina is unlikely to adhere well to these stainless surfaces. Protective coatings (e.g., DLC, black oxide) are generally unnecessary but may be added by certain manufacturers for aesthetic or additional rust-proofing, especially in saltwater environments.

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8. SIDE-BY-SIDE COMPARISON (TABLE)

Attribute	420	AUS-8
Typical Hardness (HRC)	~50–53	~57–59
Corrosion Resistance	Very Good	Very Good
Toughness	Good	Good
Edge Retention	Fair	Fair/Moderately Good
Ease of Sharpening	Excellent	Very Good

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9. IDEAL USES

420 Steel

• Budget-friendly knives intended for light-duty or infrequent use.
• Dive knives or surgical instruments needing extra corrosion resistance.
• Ideal for beginner sharpeners; 420’s softness is forgiving.
• Common in lower-cost production knives aimed at everyday tasks.

AUS-8 Steel

• General-purpose EDC knives where moderate edge retention and corrosion resistance are appreciated.
• Kitchen knives regularly exposed to moisture, acids, and detergents.
• Bushcraft or survival knives aiming for a balance between hardness and sharpenability.
• Offers a middle-ground option: harder than 420 but not as demanding or costly as premium steels.

Why Pick 420 or AUS-8 Over Other Options?

• 420: If you prioritize ease of sharpening, a low price point, and rust resistance.
• AUS-8: If you want slightly better hardness, improved edge retention, and are willing to invest a bit more time in sharpening.

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10. PROS AND CONS

10.1 420 Steel

Pros:

• Extremely easy to sharpen (friendly to beginners).
• High corrosion resistance.
• Good toughness for light-duty tasks.
• Often the most budget-friendly stainless option.

Cons:

• Frequent re-sharpening due to fair (lower) edge retention.
• Limited hardness constrains cutting performance.
• Less common in higher-end or professional knives (except enhanced variants like 420HC).

10.2 AUS-8 Steel

Pros:

• Good balance of hardness and corrosion resistance.
• Slightly better edge retention vs. 420.
• Still relatively straightforward to sharpen.
• Cost-effective alternative to premium steels.

Cons:

• Falls short in edge retention compared to higher-end alloys (e.g., S30V, 154CM).
• Sharpening requires a bit more effort than 420.
• Not as “premium” or “exotic” as certain powder metallurgy steels.

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11. CONCLUSION AND KEY TAKEAWAYS

When it comes to choosing between 420 and AUS-8, the decision hinges on your intended use, maintenance preferences, and budget:

• 420 Steel:

  • Extremely easy to sharpen and forgiving for new knife owners.
  • Excellent rust resistance in marine or humid conditions.
  • Lower edge retention means more frequent touch-ups.
  • Ideal for those wanting a very affordable stainless knife.

• AUS-8 Steel:

  • Offers a moderate step up in hardness and overall cutting performance.
  • Maintains solid corrosion resistance.
  • Slightly more complex to sharpen (but still manageable).
  • Great for EDC, kitchen, and moderate bushcraft tasks without premium-steel costs.

Neither steel requires the intensive care that high-carbon or tool steels do, although basic maintenance—like wiping blades clean and occasional lubrication—remains a good practice. If you’re looking to build sharpening skills, 420 makes an excellent stepping stone. If you want a bit more performance without breaking the bank, AUS-8 is worth a look.

Ultimately, both steels are at home in the budget-to-mid range category, each with its own strengths and compromises. Whichever you choose, you’ll have a reliably stainless blade that’s easy to maintain—an ideal combination for many everyday users.

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Additional Tips for Enthusiasts

• Compare with Other Steels: You might also consider steels like 8Cr13MoV for a similar balance of cost and performance, or 420HC for a slight upgrade over standard 420.
• Brand References:
  • 420HC: Buck Knives famously heat-treats this variant to excel beyond standard 420.
  • AUS-8: Cold Steel has historically used AUS-8 in several popular knife models.
• Real-World Scenarios: If your knife sees repeated exposure to saltwater, consider thorough rinsing and drying—even stainless steels benefit from less salt residue. In kitchen settings, remember to wash and dry promptly to ensure cleanliness and maximum longevity.

By considering these nuances and your own preferences, you’ll be well-equipped to choose a steel that perfectly aligns with your cutting needs, sharpening habits, and budget.