In the world of high-performance knife steels, MagnaCut and M390 are two of the most talked-about materials, each offering a unique blend of properties suited for different applications.
While M390 has long been celebrated for its exceptional wear resistance and corrosion resistance, MagnaCut is a newer steel designed to break traditional trade-offs in knife metallurgy by offering high toughness, excellent edge retention, and superior corrosion resistance.
This article provides an in-depth comparison between these two steels based on scientific data, including their chemical composition, performance metrics like edge retention and toughness, manufacturing processes, heat treatment requirements, and real-world performance characteristics.
By the end of this article, you’ll have a clear understanding of which steel is best suited for your needs.
Composition Analysis
The chemical composition of a steel directly influences its properties such as hardness, toughness, wear resistance, and corrosion resistance. Below is a comparison of the key alloying elements in MagnaCut and M390.
| Element | MagnaCut (%) | M390 (%) |
|---|---|---|
| Carbon (C) | 1.15 | 1.90 |
| Chromium (Cr) | 10.7 | 20.0 |
| Vanadium (V) | 4.00 | 4.00 |
| Molybdenum (Mo) | 2.00 | 1.00 |
| Niobium (Nb) | 2.00 | – |
| Tungsten (W) | – | 0.60 |
| Cobalt (Co) | – | 0.30 |
Key Alloying Elements and Their Impact
- Carbon: Higher carbon content generally increases hardness and wear resistance but can reduce toughness. M390 has a higher carbon content than MagnaCut, contributing to its superior wear resistance.
- Chromium: Chromium is critical for corrosion resistance. M390 contains significantly more chromium than MagnaCut (20% vs 10.7%), making it one of the most corrosion-resistant steels available.
- Vanadium: Both steels contain 4% vanadium, which forms hard vanadium carbides that improve wear resistance and contribute to overall hardness.
- Niobium: Unique to MagnaCut, niobium forms small carbides that enhance toughness without sacrificing wear resistance.
- Molybdenum: Present in both steels, molybdenum improves corrosion resistance and strength at high temperatures.
Direct Comparison Table
Here’s a side-by-side comparison of the key properties of MagnaCut and M390:
| Property | MagnaCut | M390 |
|---|---|---|
| Edge Retention | ~700-750 mm (CATRA) | ~750-800 mm (CATRA)[3] |
| Toughness | ~20 ft-lbs (Charpy) | ~5 ft-lbs (Charpy)[7] |
| Corrosion Resistance | Excellent | Superior |
| Maximum Hardness | 60-64 HRC[1] | 60-62 HRC[5] |
| Cost Factor | Moderate | High |
Performance Metrics
Edge Retention
Edge retention is often measured using the CATRA test, which simulates repeated cutting through abrasive materials like cardstock with silica content.
- M390: Known for its excellent edge retention due to its high volume of chromium carbides (~18% chromium carbide), M390 typically scores around 750-800 mm in CATRA tests[3].
- MagnaCut: While not as wear-resistant as M390 due to its lower carbide volume, MagnaCut still offers impressive edge retention with results in the range of 700-750 mm, placing it close to premium steels like S35VN but with better toughness[7].
Toughness
Toughness refers to a material’s ability to absorb energy before fracturing, measured via the Charpy impact test.
- M390: With a relatively high hardness level, M390 sacrifices some toughness compared to other steels. Charpy impact tests show values around 5 ft-lbs at 61 HRC, making it more prone to chipping under heavy use[7].
- MagnaCut: One of MagnaCut’s standout features is its impressive toughness for a stainless steel. It achieves Charpy impact values of approximately 20 ft-lbs at 62 HRC, making it significantly tougher than M390[7]. This allows MagnaCut to be used in thinner edge geometries without the risk of chipping or breaking.
Corrosion Resistance
Both steels are stainless due to their chromium content, but there are differences in their performance under corrosive conditions.
- M390: With its high chromium content (20%), M390 offers superior corrosion resistance compared to most other knife steels. In saltwater tests, it outperforms many other premium steels like S30V and S35VN[2].
- MagnaCut: While not as corrosion-resistant as M390 due to its lower chromium content (~10%), MagnaCut still offers excellent corrosion resistance thanks to its optimized microstructure and balanced alloying elements[1].
Hardness Range
Hardness is measured on the Rockwell C scale (HRC) and affects both wear resistance and ease of sharpening.
- M390: Typically hardened between 60-62 HRC, with some variations depending on heat treatment parameters[5].
- MagnaCut: Can be hardened between 60-64 HRC, with an optimal balance at around 62 HRC for most applications[1].
Heat Treatment Considerations
Heat treatment plays a crucial role in determining the final properties of both MagnaCut and M390.
MagnaCut Heat Treatment
MagnaCut benefits from a wide range of heat treatment options that allow knife makers to fine-tune its properties:
- Austenitizing Temperature: Between 1950°F – 2200°F (1065°C – 1205°C) with an optimal sweet spot at around 2050°F (1120°C) for achieving a balance between hardness and toughness[1].
- Tempering Cycles: Typically tempered twice at temperatures ranging from 300°F – 500°F, depending on the desired hardness.
- Quenching Media: Plate quenching or oil quenching is recommended for smaller blades to achieve maximum hardness without compromising toughness[1].
M390 Heat Treatment
M390 requires precise control during heat treatment due to its high carbide volume:
- Austenitizing Temperature: Around 2100°F (1150°C) for optimal hardness without excessive retained austenite[6].
- Tempering Cycles: Two tempering cycles are typically performed at temperatures between 400°F – 600°F, depending on whether the focus is on wear resistance or corrosion resistance[6].
- Cryogenic Treatment: Cryo treatments are often employed after quenching to reduce retained austenite and boost hardness further.
Real-World Performance
Edge Stability
Edge stability refers to how well a steel maintains its sharpness during use without deforming or chipping.
- M390: Due to its high carbide volume, M390 excels in maintaining sharpness over long periods but can be prone to chipping under heavy impact or lateral forces.
- MagnaCut: Thanks to its finer carbide structure and higher toughness, MagnaCut offers better edge stability than M390 when used in thinner edge geometries or under tougher conditions.
Sharpening Behavior
Sharpening ease is an important factor for users who frequently maintain their knives.
- M390: The large chromium carbides in M390 make it more challenging to sharpen compared to other steels like S35VN or even MagnaCut[5].
- MagnaCut: Easier to sharpen than M390 due to its finer carbide structure and lower overall carbide volume[8]. It responds well to stropping and can take a very fine edge.
Wear Patterns
Both steels exhibit different wear patterns based on their carbide distribution:
- M390: Exhibits slower wear due to its high volume of hard chromium carbides but may develop micro-chipping over time under heavy use.
- MagnaCut: Wears more evenly across the blade thanks to its balanced microstructure, making it less prone to chipping even under demanding conditions.
Practical Applications
Given their unique properties, each steel excels in different applications:
- M390: Best suited for applications requiring extreme wear resistance and corrosion protection—such as diving knives or high-end EDC knives used in harsh environments.
- MagnaCut: Ideal for applications where toughness is critical—such as hunting knives or tactical blades—while still offering excellent edge retention and corrosion resistance.
Manufacturing Considerations
Both MagnaCut and M390 are produced using powder metallurgy techniques that result in fine grain structures and uniform carbide distribution. However, there are differences in their ease of manufacturing:
Ease of Machining
Due to its higher carbide volume, M390 can be more challenging to machine compared to MagnaCut:
- M390: Requires advanced equipment like CNC machines and diamond-coated tools for effective grinding due to its high hardness[5].
- MagnaCut: Easier to machine than M390 thanks to its finer microstructure but still requires careful handling during grinding and polishing[7].
Cost Implications
The cost differences between these two steels stem from both raw material costs and manufacturing difficulty:
- M390: Generally more expensive due to its complex composition and harder machining requirements.
- MagnaCut: More affordable while still offering premium performance characteristics[7].
Heat Treatment Considerations
Heat treatment is crucial for unlocking the full potential of any knife steel. Both MagnaCut and M390 require specific heat treatment processes to optimize their properties, but there are notable differences in how they respond to these treatments.
MagnaCut Heat Treatment (Detailed)
MagnaCut’s heat treatment is relatively forgiving, offering flexibility for knife makers to fine-tune the balance between hardness, toughness, and corrosion resistance. The steel was designed by metallurgist Larrin Thomas with an emphasis on ease of heat treatment, making it accessible even to smaller custom knife makers.
- Austenitizing Temperature: MagnaCut can be austenitized at temperatures ranging from 1950°F – 2200°F (1065°C – 1205°C). The higher end of this range is used when maximum hardness is desired, while the lower end provides better toughness. For most applications, a temperature of 2050°F (1120°C) is considered optimal, balancing hardness (~62 HRC) with good toughness.
- Tempering: After quenching, MagnaCut typically undergoes two tempering cycles at temperatures between 300°F – 500°F. Lower tempering temperatures (~300°F) result in higher hardness (up to 64 HRC), while higher tempering (~500°F) sacrifices some hardness for improved toughness.
- Cryogenic Treatment: While not strictly necessary, cryogenic treatment can be used after quenching to reduce retained austenite and increase hardness. This step helps optimize edge retention without significantly affecting toughness.
M390 Heat Treatment (Detailed)
M390’s heat treatment is more demanding due to its high carbide content and complex alloying elements. Proper control of temperatures and timing is essential to avoid issues like excessive retained austenite or brittleness.
- Austenitizing Temperature: M390 is typically austenitized at around 2100°F (1150°C). This temperature ensures that enough carbides are dissolved into the matrix to provide wear resistance while minimizing retained austenite. Overheating can lead to grain growth and reduced toughness.
- Tempering: M390 requires two tempering cycles at temperatures between 400°F – 600°F, depending on the desired balance between wear resistance and corrosion resistance. Lower tempering (400°F) maximizes wear resistance, while higher tempering (600°F) improves corrosion resistance by stabilizing the chromium carbides.
- Cryogenic Treatment: Cryogenic treatment is highly recommended for M390 after quenching. This step reduces retained austenite and increases hardness by converting more of the steel’s structure into martensite. Without cryo treatment, M390 may suffer from reduced edge retention and stability.
Heat Treatment Challenges
- MagnaCut: One of MagnaCut’s advantages is its relatively simple heat treatment process. It doesn’t require cryogenic treatment or extremely precise temperature control, making it easier for small-scale knife makers to work with.
- M390: In contrast, M390 demands careful control during heat treatment. Improper austenitizing or tempering can lead to brittleness or excessive retained austenite, both of which negatively impact performance. The need for cryogenic treatment adds complexity and cost.
Real-World Performance
In real-world applications, both MagnaCut and M390 have proven themselves as top-tier steels, but they excel in different areas based on their unique compositions and properties.
Edge Geometry Impact
The geometry of a knife’s edge plays a significant role in its performance, especially when using high-performance steels like MagnaCut and M390.
- M390: Due to its high wear resistance but lower toughness, M390 performs best with slightly thicker edge geometries that provide additional support against chipping. Thin edges can be prone to micro-chipping under heavy use or impact.
- MagnaCut: Thanks to its superior toughness, MagnaCut allows for thinner edge geometries without sacrificing durability. This makes it ideal for knives that need to maintain sharpness under heavy use while still being tough enough to resist chipping.
Sharpening Characteristics
Sharpening behavior is an important consideration for knife users who frequently maintain their blades.
- M390: Due to its high volume of hard chromium carbides, sharpening M390 can be challenging. Diamond stones are often required for effective sharpening because traditional whetstones struggle with the hard carbides present in the steel. However, once sharpened, M390 holds an edge exceptionally well.
- MagnaCut: MagnaCut’s finer carbide structure makes it easier to sharpen compared to M390. It responds well to both diamond stones and traditional sharpening methods like ceramic rods or whetstones. Additionally, MagnaCut takes a very fine edge and can be stropped easily for touch-ups.
Wear Patterns
Wear patterns refer to how evenly or unevenly a steel wears down during use over time.
- M390: Due to its high carbide content, M390 tends to wear slowly but may develop micro-chipping under heavy use or lateral stress. These chips can accumulate over time, leading to uneven wear patterns that may require more frequent sharpening.
- MagnaCut: MagnaCut wears more evenly thanks to its balanced microstructure and lower carbide volume compared to M390. This results in smoother wear patterns with less risk of chipping or deformation under heavy use.
Practical Applications
Both steels are well-suited for high-performance knives but shine in different types of applications:
- M390: Best suited for applications where extreme wear resistance and corrosion protection are critical—such as diving knives, outdoor survival knives exposed to harsh environments, or premium EDC knives used in urban settings.
- MagnaCut: Ideal for applications where toughness is paramount—such as hunting knives that need to endure impact forces from cutting bone or wood—or tactical blades that need both edge retention and durability under hard use.
Manufacturing Considerations
The manufacturing processes involved in producing MagnaCut and M390 differ slightly due to their respective compositions and intended uses.
Production Method
Both steels are produced using powder metallurgy (PM), which results in fine grain structures and uniform carbide distribution. However, there are differences in ease of production:
- M390: As a PM steel with high chromium content (~20%) and large carbide volume (~18% chromium carbides), M390 requires advanced tooling during manufacturing. Machining this steel can be difficult due to its hardness and wear resistance.
- MagnaCut: Also produced using PM technology, MagnaCut benefits from a finer carbide structure that makes it easier to machine than M390. This reduces production costs slightly while still maintaining premium performance characteristics.
Cost Analysis
The cost of producing knives from either steel depends on factors like raw material availability, machining difficulty, and post-processing requirements:
- M390: Generally more expensive due to its complex composition (high chromium content) and harder machining requirements. The need for cryogenic treatment adds further costs during production.
- MagnaCut: More affordable than M390 because it’s easier to machine and doesn’t require cryogenic treatment during heat processing. However, it still commands a premium price due to its high-performance characteristics.
Conclusion
In conclusion, both MagnaCut and M390 are exceptional steels that offer unique advantages depending on the intended application:
Best Use Cases
- M390:
- Ideal for users who prioritize extreme wear resistance and corrosion protection.
- Best suited for diving knives, premium EDC knives exposed to moisture or chemicals, or collectors looking for long-lasting edge retention.
- MagnaCut:
- Perfect for those who need a tough blade capable of handling impact forces without chipping.
- Best suited for hunting knives, tactical blades used in harsh environments, or users who prefer thinner edges without sacrificing durability.
Value Proposition
While both steels offer premium performance characteristics:
- If your primary concern is maximum edge retention combined with corrosion resistance (and you don’t mind paying extra), then M390 is the better choice.
- If you want a more balanced steel offering excellent toughness along with great edge retention at a slightly lower cost—and one that’s easier to sharpen—then MagnaCut offers better overall value.
FAQs
- Which steel holds an edge longer?
- M390 holds an edge longer due to its higher carbide volume (~750–800 mm CATRA) compared to MagnaCut (~700–750 mm CATRA).
- Which steel is tougher?
- MagnaCut is significantly tougher than M390 (~20 ft-lbs vs ~5 ft-lbs Charpy impact), making it better suited for hard-use applications without chipping.
- Is MagnaCut easier to sharpen than M390?
- Yes, MagnaCut’s finer carbide structure makes it easier to sharpen than M390’s harder chromium carbides.
- Which steel has better corrosion resistance?
- M390 has superior corrosion resistance due to its higher chromium content (20% vs 10% in MagnaCut).
- Which steel is more affordable?
- MagnaCut tends to be more affordable than M390 due to easier manufacturing processes.
Citations:
[1] https://www.tophamknifeco.com/how-to-heat-treat-cpm-magnacut/
[2] https://knifesteelnerds.com/2020/06/01/m390-steel-history-and-properties-and-20cv-and-204p/
[3] https://knifesteelnerds.com/2019/10/07/catra-tests-of-m390-knives/
[4] https://bladeops.com/blog/benefits-of-magnacut-steel/
[5] https://nobliecustomknives.com/m390-steel/
[6] https://journalmt.com/pdfs/mft/2021/06/13.pdf
[7] https://knifesteelcomparison.com/m390-vs-magnacut/
[8] https://www.reddit.com/r/knifeclub/comments/w4aeij/whats_so_great_about_magnacut/
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