CPM 3V vs MagnaCut steel

CPM MagnaCut and CPM 3V are two high-performance blade steels produced by Crucible Industries using the Crucible Particle Metallurgy (CPM) process.

This powder metallurgy production method allows for more homogeneous carbide distribution and finer carbide sizes compared to conventional cast tool steels.

The key difference lies in MagnaCut’s higher alloy content including increased chromium, vanadium, niobium, and carbon compared to 3V.

This gives MagnaCut substantially greater hardness, wear resistance, and corrosion resistance, though 3V is tougher against impacts.

MagnaCut was designed by metallurgist Dr. Larrin Thomas to achieve properties similar to popular non-stainless carbon steels like CPM-4V but with stainless steel levels of corrosion resistance.

For knives requiring stainlessness along with high hardness and edge retention, MagnaCut provides an impressive combination of properties and advantages over CPM 3V.

CPM 3V vs MagnaCut steel At A Glance

Corrosion Resistance

Magnacut is a stainless steel while 3V is a non stainless steel. MagnaCut demonstrates substantially better corrosion resistance compared to CPM 3V steel.

In saltwater spray testing, MagnaCut steel showed virtually no signs of corrosion even after 72 hours of exposure.

This level of corrosion resistance exceeds other high-alloy stainless steels like 20CV and approaches “marine” grade steels.

In contrast, 3V is considered non-stainless with only 7.5% chromium content and will readily corrode without protective coatings.

The difference arises because MagnaCut contains 10.7% chromium and forms no chromium carbides during heat treatment, allowing all the chromium to provide passive protection.

CPM 3V steel has lower bulk chromium content and the formation of chromium carbides leads to depletion of chromium in the surrounding matrix. 

Therefore, MagnaCut can be used in a much wider range of environments without risk of pitting or corrosion compared to 3V.

However, CPM 3V may be preferable for limited-use knives that will not see moisture or oxidation. MagnaCut’s excellent stainless properties give it a significant advantage for general-purpose and long-term use knives.

Toughness

CPM 3V exhibits higher toughness compared to MagnaCut, though MagnaCut reaches toughness levels comparable to some non-stainless tool steels.

Testing showed 3V has impact toughness approaching shock-resistant grades like S7 steel, whereas MagnaCut is closer to steels like CPM-CruWear and CPM 4V.

At 62 HRC, MagnaCut demonstrated a Charpy impact toughness of 30 ft-lbs compared to only 26 ft-lbs for CPM-154 at 60 HRC.

The higher toughness of 3V is attributed to its lower hardness and alloy content which results in less carbide by volume.

The toughness advantage allows 3V to resist chipping and edge damage better when used for tasks involving forceful impacts.

However, MagnaCut’s toughness is sufficient to be used in a wide range of knives, and its high hardness provides better stability for thin edges.

CPM 3V steel is the preferable choice when toughness against chipping is critical, but MagnaCut reaches useful toughness levels considering its high hardness and wear resistance.

Hardness

CPM MagnaCut can achieve significantly higher hardness levels compared to CPM 3V, which allows it to obtain better edge retention and strength.

MagnaCut reaches hardness up to 64+ HRC with proper heat treatment and cold treatment, whereas 3V is limited to about 60-62 HRC.

The hardness of MagnaCut remains high across a range of austenitizing temperatures from 1950-2200°F and shows a little decrease in hardness when tempering up to 500°F. 

In contrast, 3V drops in hardness more rapidly above 1025°F tempering.

The high hardness of MagnaCut is enabled by its higher alloy content including 4% vanadium, 2% niobium, and 10.7% chromium compared to 2.75% vanadium and 7.5% chromium for 3V. 

This results in a higher volume fraction of hard carbides/carbonitrides. 

The hardness advantage of MagnaCut translates to improved edge retention and strength which allows for thinner, more acute edge geometry in knives while resisting deformation.

However, CPM 3V has greater toughness which provides some advantage in impact resistance.

In summary, MagnaCut’s much higher achievable hardness gives it substantially better wear resistance and edge holding ability compared to 3V, though 3V maintains an edge stability benefit in high-impact cutting applications.

Edge Retention

Testing shows CPM MagnaCut has significantly better edge retention and wear resistance compared to CPM 3V.

In standard CATRA cutting tests, MagnaCut demonstrated 35% higher edge retention over 440C steel, whereas 3V showed wear resistance similar to D2 steel, which has about 20% better wear resistance than 440C.

MagnaCut’s advantage stems from its higher hardness achieved through greater alloy content, allowing a higher volume of hard vanadium and niobium carbides to resist abrasive wear.

In rope-cutting tests performed by knifemakers, MagnaCut exhibited longer cutting ability before dulling compared to S30V and slightly outperformed CPM-CruWear (Z-Wear), while 3V cannot match those steels.

The high hardness and wear resistance of MagnaCut enable it to maintain sharpness incredibly well in demanding cutting tasks, though its edge may be more prone to chipping than 3V.

MagnaCut significantly outperforms 3V for edge retention and wear resistance due to its higher achievable hardness and alloy content.

However, CPM 3V steel may provide better stability against deformation in high-impact cutting.

Ease of Sharpening

Reports by knifemakers indicate CPM MagnaCut has better ease of sharpening compared to CPM 3V steel.

MagnaCut steel fine carbide structure helps reduce grinding resistance during initial edge bevel creation.

Knifemakers found MagnaCut sands easily even with coarse belts, suggesting it requires less effort to cut and grind than 3V which has larger vanadium carbides.

MagnaCut is also reported to deburr easily without stubborn burrs forming. On sharpening stones, MagnaCut responds well even to aluminum oxide abrasives rather than needing diamond or CBN.

One knifemaker directly compared sharpening MagnaCut and CPM 3V and found MagnaCut was significantly easier.

The reasons are likely MagnaCut’s finer carbide size and reduced tendency for austenite formation during heat treatment.

However, CPM 3V steel may allow a finer polished edge finish since its carbides are not as hard.

In general, the ease of grinding, deburring, and sharpening appears noticeably better with MagnaCut vs 3V due to MagnaCut’s fine carbide structure, which helps compensate for its high hardness and improves its versatility as a knife steel.

Final Thoughts on CPM 3V vs MagnaCut Steel

MagnaCut broadly outperforms 3V in hardness, edge retention, corrosion resistance, and ease of sharpening due to its higher alloy content and finer carbide structure. However, 3V steel maintains an advantage in toughness against impacts.

My personal experience with MagnaCut over the past year has been outstanding. I would recommend it to any knifemaker or enthusiast looking for stainless steel that can rival non-stainless grades in edge retention. 

The combination of properties makes it extremely versatile while still maintaining stainless characteristics.

CPM 3V will remain an excellent choice for hard-use knives where toughness against chipping is the priority, like bushcraft or survival knives.

But for general-purpose knives, MagnaCut steel’s well-rounded attributes make it a top choice in stainless steel. 

I’m very excited to see more makers utilizing MagnaCut and taking advantage of its capabilities. Spyderco has recently adopted it in its 2024 Salt series knives due to its excellent corrosion resistance.

So while 3V maintains usefulness in some applications, MagnaCut provides an all-around improvement in performance. My time with it convinces me that MagnaCut will become a highly popular knife steel.