When it comes to high-performance knife steels, CPM MagnaCut and CPM 20CV stand out as two of the most advanced options available today. Both steels are products of Crucible Industries’ powder metallurgy process, designed for exceptional performance in terms of wear resistance, edge retention, toughness, and corrosion resistance.
However, they differ in their chemical composition, heat treatment requirements, and real-world applications, making each steel more suitable for specific uses.
In this article, we will dive deep into the scientific data and measurable properties of these two steels. We will compare their chemical compositions, edge retention (CATRA test results), toughness measurements, hardness ranges, and corrosion resistance ratings.
Additionally, we will explore their manufacturing processes, heat treatment requirements, and real-world performance characteristics such as edge stability, sharpening behavior, and wear patterns. By the end of this comparison, you will have a clear understanding of which steel is better suited for your needs.
Composition Analysis
The chemical composition of a steel alloy plays a crucial role in determining its properties. Both CPM MagnaCut and CPM 20CV are stainless steels with high levels of chromium for corrosion resistance, but they differ significantly in other alloying elements.
| Element | CPM MagnaCut (%) | CPM 20CV (%) |
|---|---|---|
| Carbon (C) | 1.15 | 1.9 |
| Chromium (Cr) | 10.7 | 20.0 |
| Vanadium (V) | 2.0 | 4.0 |
| Molybdenum (Mo) | 2.0 | 1.0 |
| Tungsten (W) | – | 0.6 |
| Niobium (Nb) | 0.7 | – |
Key Alloying Elements and Their Impact
- Carbon: Higher carbon content in CPM 20CV (1.9%) contributes to its superior hardness and wear resistance compared to MagnaCut’s lower carbon content (1.15%). However, lower carbon in MagnaCut helps balance toughness and corrosion resistance.
- Chromium: CPM 20CV has a much higher chromium content (20%) than MagnaCut (10.7%), which enhances its corrosion resistance significantly but also leads to the formation of large chromium carbides that can reduce toughness.
- Vanadium: Both steels use vanadium to increase wear resistance through the formation of hard vanadium carbides. However, CPM 20CV contains more vanadium (4%) than MagnaCut (2%).
- Niobium: MagnaCut includes niobium (0.7%), which forms small niobium carbides that contribute to its fine grain structure and excellent toughness.
Performance Metrics
Edge Retention (CATRA Test Results)
Edge retention is one of the most critical properties for knife steels, especially for knives used in heavy-duty or extended cutting tasks. The CATRA test measures how long a blade retains its sharpness when cutting abrasive materials.
- CPM MagnaCut: CATRA test results for MagnaCut show edge retention in the range of 700–750 mm, placing it close to steels like S35VN but with better toughness[1][6].
- CPM 20CV: CPM 20CV excels in edge retention due to its high volume of vanadium carbides. CATRA test results typically show CPM 20CV scoring around 180, significantly higher than many other steels[3][7].
Toughness Measurements
Toughness refers to a steel’s ability to resist chipping or breaking under stress or impact.
- CPM MagnaCut: Known for its exceptional toughness, MagnaCut matches or exceeds the toughness of many non-stainless tool steels like CPM-4V and Vanadis 4 Extra[1]. It performs well even at high hardness levels (~63–64 HRC)[1].
- CPM 20CV: While CPM 20CV offers good toughness for a high-hardness stainless steel, it is not as tough as MagnaCut due to its higher carbide volume[2]. It is more prone to chipping under heavy impact or lateral stress[2][7].
Corrosion Resistance
Corrosion resistance is another key factor for knife steels used in humid or coastal environments.
- CPM MagnaCut: With around 10–13% chromium “in solution,” MagnaCut offers excellent corrosion resistance that rivals even some dedicated corrosion-resistant steels like LC200N[1]. It is highly resistant to rusting even in saltwater environments[4].
- CPM 20CV: Thanks to its high chromium content (20%), CPM 20CV also provides excellent corrosion resistance but is slightly less resistant than MagnaCut due to the presence of larger chromium carbides that reduce overall corrosion protection[2][5].
Hardness Range
Hardness is measured on the Rockwell C scale (HRC) and affects both edge retention and toughness.
- CPM MagnaCut: Typically hardened between 60–64 HRC, with an optimal balance at around 62–63 HRC, making it suitable for both hard-use knives and kitchen knives[1][4].
- CPM 20CV: Usually hardened between 59–61 HRC, offering a balance between hardness and toughness but not reaching the same high hardness levels as MagnaCut without sacrificing toughness[3][5].
Direct Comparison Table
Here’s a side-by-side comparison of key properties:
| Property | CPM MagnaCut | CPM 20CV |
|---|---|---|
| Edge Retention | ~700–750 mm CATRA | ~180 CATRA |
| Toughness | Superior | Good |
| Corrosion Resistance | Excellent | Very Good |
| Maximum Hardness | ~64 HRC | ~61 HRC |
| Cost Factor | Moderate | High |
Heat Treatment Considerations
Heat treatment is a critical step that determines how well a steel performs in real-world applications.
CPM MagnaCut Heat Treatment
MagnaCut benefits from relatively straightforward heat treatment protocols:
- Austenitizing Temperature: Around 2050°F is recommended for general use[1].
- Tempering Temperature: Tempering at around 400°F–500°F yields an optimal balance between hardness (~62–64 HRC) and toughness[1].
- Cryo Treatment: Cryogenic treatment can be used to maximize hardness without sacrificing toughness significantly[1].
CPM 20CV Heat Treatment
Heat treating CPM 20CV requires careful attention due to its high carbide content:
- Austenitizing Temperature: Typically around 2150°F–2200°F, allowing full dissolution of carbides into the matrix[5].
- Tempering Temperature: Tempering at lower temperatures (~350°F) helps maintain maximum hardness (~61 HRC), but higher tempering temperatures can improve toughness at the cost of some hardness[5].
- Cryo Treatment: Cryogenic treatment is often necessary to reduce retained austenite and improve wear resistance without compromising corrosion resistance[5].
Real-World Performance Characteristics
Edge Stability
Edge stability refers to how well a blade resists deformation or chipping under stress:
- CPM MagnaCut: Thanks to its fine carbide structure and balanced properties, MagnaCut exhibits excellent edge stability even at thin edge geometries, making it ideal for precision cutting tasks like filleting or slicing[6].
- CPM 20CV: While CPM 20CV offers good edge stability due to its hardness, it can be prone to micro-chipping if used on hard materials like bone or metal[7].
Sharpening Behavior
Sharpening ease is an important consideration for users who regularly maintain their knives:
- CPM MagnaCut: Easier to sharpen than many high-carbide steels due to its finer grain structure. Conventional sharpening stones can be used effectively[4][6].
- CPM 20CV: More difficult to sharpen because of its high carbide volume. Diamond stones or ceramic sharpeners are recommended for maintaining an edge on CPM 20CV blades[3][7].
Wear Patterns
Wear patterns refer to how evenly a blade wears down over time with use:
- CPM MagnaCut: Wears more evenly thanks to its balanced combination of wear resistance and toughness, making it ideal for repeated cutting tasks without noticeable degradation over time[6].
- CPM 20CV: Exhibits slower wear but may develop micro-chips along the edge when used on harder materials due to its brittleness at high hardness levels[7].
Conclusion
Both CPM MagnaCut and CPM 20CV are outstanding knife steels with unique strengths:
- If you need a steel that excels in toughness, corrosion resistance, and edge stability, especially for hard-use knives like survival blades or kitchen knives exposed to moisture, then CPM MagnaCut is the superior choice.
- On the other hand, if your priority is edge retention above all else—especially for tasks requiring long-lasting sharpness such as hunting or EDC knives—then CPM 20CV would be more suitable despite being harder to sharpen.
Ultimately, your choice should depend on your specific needs—whether you prioritize ease of maintenance and versatility (MagnaCut) or extreme wear resistance and edge retention (20CV).
FAQs
- Which steel holds an edge longer?
- While both offer excellent edge retention, CPM 20CV outperforms MagnaCut due to its higher carbide volume.
- Which steel is easier to sharpen?
- CPM MagnaCut is easier to sharpen thanks to its finer grain structure compared to the harder-to-sharpen CPM 20CV.
- Which steel has better corrosion resistance?
- Both offer excellent corrosion resistance; however, MagnaCut slightly edges out due to its optimized chromium solution.
- Which one is tougher?
- CPM MagnaCut provides superior toughness compared to CPM 20CV.
- Which steel is better for hard-use knives?
- For hard-use applications where impact resistance is critical, CPM MagnaCut is the better choice.
Citations:
[1] https://knifesteelnerds.com/2021/03/25/cpm-magnacut/
[2] https://bladeops.com/cpm-20cv/
[3] https://knifeup.com/how-good-is-cpm-20cv-knife-steel/
[4] https://www.knifeart.com/magnacut.html
[5] https://nobliecustomknives.com/cpm-20cv/
[6] https://knifesteelcomparison.com/m390-vs-magnacut/
[7] https://knifesteelcomparison.com/20cv-vs-s30v/
Leave a Reply