What Steel to Use for a Folding Knife? A Guide to the Best Types

How to choose steel for a folder?

When we talk about what characterizes the best folding knife, we will certainly mention parameters such as a reliable locking mechanism, durable bearings, or blade geometry, but every premium folder knife must have a blade made of the most durable steel possible for the task. Choosing the right steel for a folding knife is key to choosing a tool that will serve for years. Steel determines not only the strength of the blade, but also the ease of sharpening, corrosion resistance and maintaining sharpness over a long period of use. Let's look at the most important parameters and popular types of steel that are used in top-class knives.

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Division of knife steels. Different types of steel used in folding knives

Before we get into MagnaCut steel itself, it’s worth understanding the basic types of steel that are used in folding knife manufacturing:

1. Carbon steels (low alloy) – steels in which the main element, apart from iron, is carbon. They are characterized by high hardness and ease of sharpening, but are susceptible to corrosion and lose their sharpness more quickly due to the lack of wear-resistant alloy additives. They usually contain iron carbides, i.e. cementite. They require regular maintenance to prevent rusting.

2. Alloy steels (high-alloy steels) – steels that contain various alloying additives (e.g. molybdenum, vanadium), which improve their resistance to abrasive wear and corrosion, which varies depending on the composition. They often offer the best mechanical parameters of the knife, and their rust is much less troublesome than carbon steels.

3. Stainless steel – these are also high-alloy steels, but with a significant amount of chromium in the solution, which creates a passive protective layer of steel. They usually have good sharpness, although the chromium carbides that predominate in them are not as hard as carbides of elements such as vanadium, niobium, or tungsten, which occur in alloy steels. An exception is MagnaCut, a steel that combines the possession of the hardest carbides with excellent corrosion resistance.

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The most important parameters of steel for a folding knife

The most important parameters of steel for a folding knife are:

1. Sharpness – the ability of steel to maintain a cutting edge for a long time. The better the sharpness, the less often the knife needs to be sharpened. It is influenced by both the hardness of the steel and the amount and type of carbides. Additionally, it depends not only on the type of steel but also on the geometry of the knife.
2. Impact strength (ductility) – resistance of steel to mechanical damage, such as cracks or chipping. Thanks to good impact strength, the knife can have thinner geometry behind the cutting edge, which translates into better cutting ability while maintaining resistance to chipping. Additionally, if we want to obtain the hardest knife possible, i.e. a knife with a hardness of 62 HRC and more, then increasing hardness also increases brittleness. However, if we choose a steel grade with high impact strength, the risk of chipping of the cutting edge decreases.
3. Corrosion resistance – especially important in knives used in difficult conditions, where the blade is exposed to moisture and other atmospheric factors. Corrosion, in addition to impairing the aesthetics of the knife, can also affect its sharpness. The cutting edge becomes rounded as it corrodes. Corrosion dulling is an undesirable phenomenon, but at the same time common in carbon steel knives used in chemically aggressive environments. For this reason, high-alloy semi-stainless steels and stainless tool steels are recommended in pocket knives.

Secondly, it is also worth paying attention to:

1. Hardness - resistance to plastic deformation, e.g. rolling or bending of the cutting edge. In combination with high impact steel we can obtain high stability of the cutting edge, i.e. resistance to rolling and chipping. Greater knife hardness also improves sharpness retention.
2. Ease of sharpening - hard-wearing steels need to be sharpened longer to get a sharp knife again and it is usually necessary to use diamond sharpeners instead of natural stones. On the other hand, the key moment of sharpening is "removing the wire" (burr or burr) and while in softer steels we will quickly reach this point by sharpening, the wire itself can be easier to remove in harder steel, because in softer types it behaves like foil and instead of breaking off it bends left and right.

There is no "ideal" steel that would be the best in every respect. The choice of steel is always a compromise between different properties. However, in folding knives, steels with the best balance in terms of impact strength, sharpness retention, and rust resistance are recommended

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Powder Steel vs. Conventional Steel: Example D2 and CPM-D2

Traditional steel is obtained by melting and casting and hot rolling. It has larger grains and a less uniform distribution of carbides, which can reduce its impact strength.

Powder steel is made of powder sintered under high pressure, which limits the growth of grain in each particle of powdered steel. Grains cannot form larger structures. Thanks to this, the structure of the steel is finer and more uniform, which provides higher impact strength.

An example that well illustrates the differences in steel production technology is D2 steel. It comes in two variants: traditional and powder CPM-D2 or D2-PM.

Both variants have the same chemical composition, meaning that they have similar levels of sharpness and corrosion resistance. However, thanks to the use of powder technology, which reduces the grain and carbide size, CPM-D2 steel offers around twice the impact strength of its traditional counterpart. The higher impact strength allows for thinner cutting edges, increasing cutting ability, and hardening the knife to a higher hardness with less risk of chipping, thus increasing the stability of the cutting edge.

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The best steel grades for folding knives

1. MagnaCut

This is one of the latest breakthroughs in steel technology, combining excellent edge retention, high corrosion resistance and excellent impact strength. This is a steel so unique that we will devote an entire separate article to it.

2. Elmax

Powder steel produced by the Swedish company Uddeholm. It combines high abrasion resistance with good impact strength and high corrosion resistance. Due to the balance of these features, it is often chosen for premium folding knives and blades intended for intensive use. Despite its good parameters, it is also not as expensive as other stainless powder steels. Similar to S45VN steel

3. M390 and M398

These two types of powder steel are often chosen for premium knives. They offer excellent edge retention due to their high carbide content and very good corrosion resistance.

• M390 is more versatile thanks to its higher impact strength.
• The M398 has even better sharpness, but at the cost of being slightly more fragile.

Similar parameters will be the American equivalents such as CPM S30-V, S60-V, S90-V, S110V

4. Vanadis 4 Extra

This powder tool steel from the Swedish manufacturer Uddeholm is distinguished by its excellent balance between impact strength and sharpness, achieved thanks to record-hard vanadium carbides. Semi-stainless steel ideal for intensive use, where strength and durability of the blade count. Vanadis, similarly to CPM 4V steel, is considered the most balanced knife steel for most applications.

5. K390

Known for its excellent sharpness and incredible abrasion resistance, BÖHLER's semi-stainless powder steel. However, K390 is less resistant to corrosion, which means that it requires regular maintenance. Very similar to Vanadis 8 or CPM 10V.

6. AEB-L

Steel valued for its excellent cutting properties, thanks to its record-breaking impact strength, and consequently the ability to obtain a very thin cutting edge. It also has very good corrosion resistance. Knives with high impact strength and high hardness also offer excellent cutting edge stability. The equivalent of the steel is 13C26 and is also similar in parameters to 14C28N.

7. N690

Austrian stainless steel with high corrosion resistance and easy sharpening. It is often used in folding knives due to its fairly good sharpness retention, thanks to the high content of chromium carbides. It is also popular due to its affordable price for the offered performance. Parameters similar to Japanese VG10 steel.

8. D2

Classic, semi-stainless tool steel, known for its quite good abrasion resistance. Used for many years in field knives, kitchen knives and folders, but also in the tool industry, where it is better known under the name NC11LV. It works well in everyday knives, but requires more care in a humid environment. It is also produced by Böhler under the name K110.

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Why is it worth choosing steel with good impact resistance in folding knives?

High impact steel allows the creation of blades with thin geometry behind the cutting edge, which significantly improves cutting ability. At the same time, it reduces the risk of blade chipping, even with intensive use. In addition, high impact strength allows the steel to be hardened to a higher hardness without increasing the risk of cracks.

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Summary

The choice of steel for a folding knife should depend on the individual needs of the user and the way of use. Grades such as MagnaCut, Vanadis 4 Extra, K390, AEB-L, Elmax, M390 or M398 offer unique properties that will meet the expectations of even the most demanding customers. However, if you want slightly more budget-friendly options, steels such as N690, D2 or A8 mod are still great choices.

Regardless of the choice, well-chosen steel is the basis of a knife that not only looks good, but above all works well in practice, which means that its blade will withstand heavy loads and the cutting edge will remain razor-sharp for a long time.