In the world of premium knife steels, CPM 20CV and S35VN stand out as two of the most popular choices for knife enthusiasts, professionals, and manufacturers alike. Both steels are well-regarded for their high-performance characteristics, but they cater to slightly different needs.
CPM 20CV is known for its outstanding edge retention and corrosion resistance, while S35VN offers a more balanced performance with better toughness and ease of sharpening.
This article will provide a detailed comparison between these two steels, focusing on their chemical composition, performance metrics, heat treatment requirements, and real-world applications. We will also explore the differences in manufacturing processes and cost implications. By the end, you’ll have a clear understanding of which steel is best suited for your needs.
Composition Analysis
The chemical composition of a steel plays a significant role in determining its performance characteristics such as hardness, toughness, wear resistance, and corrosion resistance. Let’s begin by comparing the chemical makeup of CPM 20CV and S35VN.
| Element | CPM 20CV (%) | S35VN (%) |
|---|---|---|
| Carbon (C) | 1.9 | 1.4 |
| Chromium (Cr) | 20.0 | 14.0 |
| Vanadium (V) | 4.0 | 3.0 |
| Molybdenum (Mo) | 1.0 | 2.0 |
| Niobium (Nb) | – | 0.5 |
- Carbon (C): Carbon increases hardness and edge retention in both steels, but CPM 20CV has a higher carbon content (1.9%) compared to S35VN (1.4%), contributing to its superior wear resistance.
- Chromium (Cr): Chromium is crucial for corrosion resistance. CPM 20CV contains an impressive 20% chromium, making it one of the most corrosion-resistant steels available[2][4]. In contrast, S35VN has a lower chromium content at 14%, which still provides good corrosion resistance but not at the same level as CPM 20CV.
- Vanadium (V): Both steels contain vanadium, which forms hard vanadium carbides that improve wear resistance and toughness. CPM 20CV has slightly more vanadium (4%) than S35VN (3%), further enhancing its edge retention[2][4].
- Molybdenum (Mo): Molybdenum improves strength and toughness at high temperatures. S35VN has double the molybdenum content of CPM 20CV, contributing to its superior toughness[3].
- Niobium (Nb): One of the key differences is the addition of niobium in S35VN, which refines the grain structure and improves toughness without sacrificing hardness[4].
Performance Metrics
Edge Retention
Edge retention is one of the most critical factors for knife users who need their blades to stay sharp over extended periods.
- According to CATRA tests (a standard method for measuring edge retention), CPM 20CV outperforms S35VN significantly due to its higher vanadium carbide content[6]. In real-world tests, CPM 20CV scored around 960 cuts before dulling, while S35VN scored approximately 760 cuts[7]. This makes CPM 20CV ideal for tasks requiring long-lasting sharpness.
Toughness
Toughness measures a steel’s ability to resist chipping or breaking under stress.
- S35VN is known for its excellent toughness, largely due to the addition of niobium and its balanced alloy composition[4]. It is approximately 15-20% tougher than its predecessor, S30V, and significantly tougher than CPM 20CV[3]. This makes it more suitable for heavy-duty tasks where impact resistance is important.
Corrosion Resistance
Corrosion resistance is essential for knives used in humid or marine environments.
- With its higher chromium content (20%), CPM 20CV offers superior corrosion resistance compared to S35VN[2][7]. This makes it an excellent choice for environments where moisture exposure is frequent.
Hardness Range
Hardness is typically measured on the Rockwell C scale (HRC). Higher hardness generally translates to better edge retention but can reduce toughness.
- CPM 20CV typically achieves a hardness range of 59-61 HRC, depending on heat treatment[6]. This high hardness contributes to its exceptional wear resistance.
- S35VN usually falls within the range of 58-61 HRC, offering a good balance between hardness and toughness[4].
Heat Treatment Considerations
Heat treatment plays a crucial role in unlocking the full potential of any steel. Both CPM 20CV and S35VN require precise heat treatment processes to achieve their optimal properties.
Optimal Heat Treatment Parameters
- CPM 20CV: This steel benefits from austenitizing temperatures between 2050°F and 2150°F, followed by quenching and tempering at around 400°F for maximum hardness[6]. Cryogenic treatment can further enhance wear resistance by transforming retained austenite into martensite.
- S35VN: For optimal results, S35VN should be heat-treated at temperatures between 1950°F and 2050°F, with tempering at around 400°F to achieve a balance between hardness and toughness[3].
Heat Treatment Challenges
Both steels require careful control during heat treatment:
- For CPM 20CV, achieving uniform carbide distribution can be challenging due to its high alloy content. Improper heat treatment may result in brittleness or reduced edge retention[6].
- S35VN is easier to heat treat due to its more balanced composition but still requires attention to avoid over-tempering, which could reduce both hardness and corrosion resistance[3].
Real-World Performance
Edge Stability
Edge stability refers to how well a blade maintains its geometry under use without chipping or rolling.
- CPM 20CV’s high hardness gives it excellent edge stability under light cutting conditions but makes it more prone to chipping when subjected to heavy impacts or lateral forces[5].
- S35VN’s superior toughness allows it to maintain edge stability even under more demanding conditions like chopping or batoning[4].
Sharpening Behavior
Sharpening ease is an important consideration for many users.
- Due to its high wear resistance, CPM 20CV can be difficult to sharpen without diamond abrasives[5]. However, once sharpened, it holds an edge for an exceptionally long time.
- S35VN is easier to sharpen than CPM 20CV thanks to its lower carbide volume and balanced alloy composition[3][5]. This makes it more user-friendly for those who frequently sharpen their knives.
Wear Patterns
Wear patterns refer to how evenly or unevenly a blade wears down during use.
- CPM 20CV tends to wear down slowly and evenly due to its high vanadium carbide content, making it ideal for precision cutting tasks that require long-term sharpness[2].
- S35VN wears more uniformly across various tasks but may dull faster than CPM 20CV in abrasive environments due to its lower wear resistance[4].
Practical Applications
The practical applications of each steel depend on their performance characteristics:
- CPM 20CV excels in applications where long-lasting sharpness and corrosion resistance are paramount—such as in fishing knives or folding knives used in wet environments.
- S35VN, with its superior toughness and ease of sharpening, is better suited for heavy-duty tasks like bushcraft or tactical knives where durability under stress is critical.
Manufacturing Considerations
Both steels are produced using Crucible Particle Metallurgy (CPM), which ensures fine carbide distribution and consistent quality across batches.
Production Method
The powder metallurgy process used for both steels involves melting the alloy components together before atomizing them into fine particles. These particles are then hot-isostatically pressed into solid ingots before being rolled into sheets or bars suitable for knife production[6].
Cost Implications
CPM steels are generally more expensive than conventionally produced steels due to the complexity of the powder metallurgy process:
- CPM 20CV tends to be more expensive than S35VN because it contains higher amounts of costly elements like chromium and vanadium[1][7].
Direct Comparison Table
| Property | CPM 20CV | S35VN |
|---|---|---|
| Edge Retention | Very High | High |
| Toughness | Moderate | High |
| Corrosion Resistance | Very High | High |
| Maximum Hardness | ~61 HRC | ~60 HRC |
| Cost Factor | Higher | Moderate |
Conclusion
In conclusion, both CPM 20CV and S35VN offer excellent performance characteristics but cater to different needs:
- Choose CPM 20CV if you prioritize edge retention and corrosion resistance over ease of sharpening or toughness.
- Choose S35VN if you need a tougher blade that can withstand impact without chipping while still offering good edge retention and ease of sharpening.
For users looking for an all-around performer that balances durability with ease of maintenance, S35VN is likely the better choice. However, if you’re after extreme edge retention in less demanding cutting tasks or corrosive environments, CPM 20CV will serve you well.
Citations:
[1] https://forum.spyderco.com/viewtopic.php?t=94034
[2] https://nobliecustomknives.com/cpm-20cv/
[3] https://www.shieldon.net/s35vn-vs-m390-steel-which-one-is-better/
[4] https://www.knifeart.com/s35vn-vs-20cv.html
[5] https://www.youtube.com/watch?v=aqy4DcRgr9U
[6] https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by-a-metallurgist-toughness-edge-retention-and-corrosion-resistance/
[7] https://www.bladeforums.com/threads/s35vn-vs-cpm20cv.1609843/
[8] https://www.reddit.com/r/knives/comments/15xf2do/what_is_your_goto_blade_steel/
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