Knife Steel Selection
Let’s get one thing straight there is no such thing as the best knife steel, there are however steels that perform better in certain situations and environment’s than others, then you also have to contend with preconceived ideas and opinions the following is to guide in your selection of knife steel for your particular project
What Makes A Knife Steel Perform
The search for higher-performance steels has always been a matter of personal preference and opinion for the knife maker, but you must remember that the steels we have available today were not developed for the knife maker, they were developed to fill a particular need in industry, thankfully because of the needs of industry we have some absolutely fantastic steels that are very well suited to our needs. Steel by itself isn’t the sole determiner of knife performance, of course.
Heat treatment, blade geometry, handles geometry and materials all effect how a knife steel performs for a particular job. However, those other qualities can be difficult to measure. You can’t tell by looking at it how well a blade has been heat-treated, and you can only make educated guesses on how well the blade and handle geometry will work. With steel, however, you can get a full listing of its alloying elements, something measureable and quantifiable
As a result, it’s easy to fall into the trap of putting too much emphasis on the steel itself. A knife is more than steel, and it’s important not to forget that. In addition, many modern steels perform so well, that knife decisions can often be made based on other factors, than marginal increases in steel performance.
The question of “what’s the best knife steel” or “rank the following steels in order from best to worst” often comes up. The resulting replies can never be totally accurate, because depending on the jobs the knife will be used for, the blade geometry, and the quality of the heat treat, what is “best” and what is “worst” can be very subjective. If you want to make an educated decision about steels, try to learn the basics of steel properties, and go from there.
Sharpening for Performance
That doesn’t mean that significant performance advantages can’t be had by choosing the right steel for the job. In fact, choosing steel can significantly impact the performance of a knife. But, to really bring out the performance of particular steel, you need to take advantage of the better steel in your sharpening plan. If a weak, brittle steel can perform the job when sharpened at 25-degrees-per-side, a strong, tough steel might give you some marginal performance improvements if it, too, is sharpened at 25-degrees-per-side. However, to really bring out the performance of the better steels, trying bringing it down to 20-degrees per side, or less. The advantage of the better steel is that it is strong and tough enough to hold up with a small edge angle — and smaller edge angles radically out-perform bigger edge angles. It’s easy to get a 10-to-1 perform advantage for certain cutting jobs by cutting 5 degrees off your sharpening angle.
Design for Performance
In the section above, we highlighted what the user can do to bring out the best performance in high-performance steel. But the user is only half the equation; now we will look at what the knifemaker might do with higher-performance steel. As the knifemaker moves from one steel to another, it is often possible to modify the design of a particular knife to take advantage of the newer steel, and raise performance.
For example, it is possible to make a hard-use “tactical/utility” knife from ATS-34. To make sure the ATS-34 will take the kind of stresses it might see in this environment, the edge might be left a bit thick (sacrificing cutting performance), or the hardness brought down a touch (sacrificing strength and wear resistance), or both. If the same maker moves to much-tougher S30V, he might be able to thin out the edge, thin out the entire knife, and raise the hardness, bringing up performance as a whole. Moving to differentially-tempered 5160 might allow the maker to re-profile even more for performance. If we’re talking about a fighter, moving from 1095 to 3V might allow the maker to make the knife much thinner, lighter, and faster, while significantly increasing cutting performance and maintaining edge integrity.
So to really take advantage of the higher-performance steel, we want the knifemaker to adjust the knife design to the steel, wherever he thinks it’s appropriate. If a knifemaker offers the same knife in multiple steels, ask about what the characteristics are in each steel, and the how’s and why’s of where the design has changed to accommodate each steel offered.
Note that there can be good reasons that a knifemaker might not change the blade profile even though the steel has changed. Maybe he’s particularly good at heat-treating one steel or another, so that the differences between disparate steels are minimized. Maybe the higher-performance steel is not available in the next stock thickness down. Maybe instead of higher cutting performance, the maker would rather offer the same cutting performance but in a knife that can take more abuse. Maybe his customers tend to only buy thicker knives regardless of performance.
So work with the maker to understand the choices being made with the different steels being offered. If you understand the kind of performance you need, you’ll be able to make a wise choice. What is it we’re looking for in steel, anyway? Well, what we are looking for is strength, toughness, wear resistance, and edge holding. Sometimes, we’re also looking for stain resistance.
Just like it sounds, wear resistance is the ability to withstand abrasion. Generally speaking, the amount, type, and distribution of carbides within the steel are what determine wear resistance.
Strength The ability to take a load without permanently deforming. For many types of jobs, strength is extremely important. Any time something hard is being cut, or there’s lateral stress put on the edge, strength becomes a critical factor. In steels, strength is directly correlated with hardness the harder the steel,
the stronger it is. Note that with the Rockwell test is used to measure hardness in a steel, it is the hardness of the steel matrix being measured, not the carbides. Thus, it’s possible for a softer, weaker steel (measuring low on the Rockwell scale) to have more wear resistance than a harder steel. S60V, even at 56 RC, still has more and harder carbides than ATS-34 at 60 RC, and thus the S60V is more wear resistant, while the ATS-34 would be stronger.
The ability to take an impact without damage, by which we mean, chipping, cracking, etc. Toughness is obviously important in jobs such as chopping, but it’s also important any time the blade hits harder impurities in a material being cut (e.g., cardboard, which often has embedded impurities).
The knife maker will be making a trade of between strength and toughness. Generally speaking, within the hardness range that the steel performs well at, as hardness increases, strength also increases, but toughness decreases. This is not always strictly true, but as a rule of thumb is generally accurate. In addition, it is possible for different heat treat formulas to leave the steel at the same hardness, but with properties such as toughness, wear resistance, and stain resistance significantly differing.
(Rust resistance): The ability to withstand rust (oxidation). Obviously, this property can be helpful in corrosive environments, such as salt water. In addition, some types of materials are acidic (e.g., some types of foods), and micro-oxidation can lead to edge loss at the very tip of the edge, over a small amount of time. In “stainless” cutlery steels, stain resistance is most affected by free chromium — that is, chromium that is not tied up in carbides. So, the more chromium tied up in carbides, the less free chromium there is, which means more wear resistance but less stain resistance.
Edge Holding Ability
The ability of a blade to hold an edge. Many people make the mistake of thinking wear resistance and edge holding are the same thing. Most assuredly, it is not; or rather, it usually is not. Edge holding is job-specific. That is, edge holding is a function of wear resistance, strength, and toughness. But different jobs require different properties for edge holding. For example, cutting through cardboard (which often has hard embedded impurities); toughness becomes extremely important, because micro-chipping is often the reason for edge degradation. Whittling very hard wood, strength becomes very important for edge-holding, because the primary reason for edge degradation is edge rolling and impaction. Wear resistance becomes more important for edge holding when very abrasive materials, such as carpet, are being cut. And for many jobs, where corrosion- inducing materials are contacted (such as food prep), corrosion can affect the edge quickly, so corrosion resistance has a role to play as well.
There Are Other Properties That Significantly Affect How Knife Steel Performs
Ability to take an edge
Some steels just seem to take a much sharper edge than other steels, even if sharpened the exact same way. Finer-grained steels just seem to get scary sharp much more easily than coarse-grained steels, and this can definitely affect performance. Adding a bit of vanadium is an easy way to get fine-grained steel. In addition, an objective of the forging process is to end up with finer-grained steel. So both steel choice, and the way that steel is handled, can affect cutting performance.
Cleaner, purer steels perform better than dirtier, impure steels. The cleaner steel will often be stronger and tougher, having less inclusions. High quality processes used to manufacture performance steel include the Argon/Oxygen/Decarburization (AOD) process, and for even purer steel, the Vacuum Induction Melting/Vacuum Arc Remelting (VIM/VAR) process, often referred to as double vacuum melting or vacuum re-melting.Some steels seem to cut aggressively even when razor polished. For these steels, even when they’re polished for push-cutting, their carbides form a kind of “micro serrations” and slice aggressively.
What’s The “Best Knife Steel”?
Understanding these properties will get you started to fundamentally understanding steels and how choice of steel can affect performance. I often see people asking, what’s the best steel? Well, the answer depends so much on what the steel is being used for, and how it’s heat-treated, that the questioner can never possibly get an accurate answer. For a knife lover, it’s worth spending a little time understanding steel properties — only by doing so well he really understands what the “best steel” might be for his application.
Putting it all together, you can see how these properties might determine your steel choice. To pick on S60V and ATS-34 again, there seems to be a feeling that S60V is “better” in some absolute sense than ATS-34. But S60V is often left very soft, around 55-56 RC, to make up for a lack of toughness. Even left that soft, an abundance of well-distributed vanadium carbides gives S60V superior wear resistance to ATS-34, at acceptable toughness levels. However, does that mean S60V is “better” than ATS-34? Well, many users will find edge rolling and impaction the primary causes of edge degradation for everyday use. For those users, even though S60V is more wear-resistant, S60V is also so soft and weak that they will actually see better edge retention with ATS-34! The S60V user can leave the edge more obtuse (raise the sharpening angle) to put more metal behind the edge to make it more robust, but now the S60V will suffer serious cutting performance disadvantages versus the thinner ATS-34 edge.
So, The Next General Rule:
Knowing the uses you’ll put your knife to, and exactly how those uses cause edge degradation, will allow you to make a much better choice of steel, if you generally understand steel properties.
The properties of different steels will be laid out below. But in your search for the knife with the “best steel” for your uses, I always suggest you ask the makers of the knives you’re considering which steels they would use. The knife maker will usually know which steels he can make perform the best. And as pointed out above, heat treat is absolutely critical to bringing out the best in steel. A maker who has really mastered one particular steel (e.g., Dozier and D2) might be able to make that steel work well for many different uses. So never go just by charts and properties; make sure you also consider what the knife maker can do with the steel.
Elements Of Steel
At its most simple, steel is iron with carbon in it. Other alloys are added to make the steel perform differently. Here are the important steel alloys in alphabetical order, and some sample steels that contain those alloys:
Present in all steels, it is the most important hardening element. Also increases the strength of the steel but, added in isolation, decreases toughness. We usually want knife-grade steel to have >.5% carbon, which makes it “high-carbon” steel.
Added for wear resistance, hardenability, and (most importantly) for corrosion resistance. A steel with at least 13% chromium is typically deemed “stainless” steel, though another definition says the steel must have at least 11.5% *free* chromium (as opposed to being tied up in carbides) to be considered “stainless”. Despite the name, all steel can rust if not maintained properly. Adding chromium in high amounts decreases toughness. Chromium is a carbide-former, which is why it increases wear resistance.
An important element, manganese aids the grain structure, and contributes to hardenability. Also adds strength & wear resistance. Improves the steel (e.g., deoxidizes) during the steel’s manufacturing (hot working and rolling). Present in most cutlery steel except for A2, L-6, and CPM 420V.
A carbide former, prevents brittleness & maintains the steel’s strength at high temperatures. Present in many steels, and air-hardening steels (e.g., A2, ATS-34) always have 1% or more molybdenum — molybdenum is what gives those steels the ability to harden in air.
Ad’s toughness. Present in L-6 and AUS-6 and AUS-8. Nickel is widely believed to play a role in corrosion resistance as well, but this is probably incorrect.
Present in small amounts in most steels, phosphorus is an essentially a contaminant which reduces toughness.
Contributes to strength. Like manganese, it makes the steel more sound while it’s being manufactured.
Typically not desirable in cutlery steel, sulphur increases machinability but decreases toughness.
Carbide former, it increases wear resistance. When combined properly with chromium or molybdenum, tungsten will make the steel to be high-speed steel. The high-speed steel M2 has a high amount of tungsten. The strongest carbide former behind vanadium.
Contributes to wear resistance and hardenability, and as a carbide former (in fact, vanadium carbides are the hardest carbides) it contribute to wear resistance. It also refines the grain of the steel, which contributes to toughness and allows the blade to take a very sharp edge. A number of steels have vanadium, but M2, Vascowear, and CPM T440V and 420V (in order of increasing amounts) have high amounts of vanadium. BG-42’s biggest difference with ATS-34 is the addition of vanadium.
Non-stainless Knife Steel (carbon, alloy, and tool steels):
These steels are the steels most often forged. Stainless steels can be forged (guys like Sean McWilliams do forge stainless), but it is very difficult. In addition, carbon steels can be differentially tempered, to give a hard edge-holding edge and a tough springy back. Stainless steels are not differentially tempered. Of course, carbon steels will rust faster than stainless steels, to varying degrees.
In the AISI steel designation system, 10xx is carbon steel; any other steels are alloy steels. For example, the 50xx series are chromium steels.
In the SAE designation system, steels with letter designations (e.g., W-2, A2) are tool steels.
There is an ASM classification system as well, but it isn’t seen often in the discussion of cutlery steels, so I’ll ignore it for now. Often, the last numbers in the name of steel are fairly close to the steel’s carbon content. So 1095 is ~.95% carbon. 52100 is ~1.0% carbon. 5160 is ~.60% carbon.
1095 (and 1084, 1070, 1060, 1050, etc.) Many of the 10-series steels for cutlery, though 1095 is the most popular for knives. When you go in order from 1095-1050, you generally go from more carbon to less, from more wear resistance to less wear resistance, and tough to tougher to toughest. As such, you’ll see 1060 and 1050, used often for swords. For knives, 1095 is sort of the “standard” carbon steel, not too expensive and performs well. It is reasonably tough and holds an edge well, and is easy to sharpen. It rusts easily. This is simple steel, which contains only two alloying elements: .95% carbon and .4% manganese. The various Kabars are usually 1095 with a black coating.
A steel popular with forgers, it is popular now for a variety of knife styles, but usually bigger blades that need more toughness. It is essentially a simple spring steel with chromium added for hardenability. It has good wear resistance, but is known especially for its outstanding toughness. This steel performs well over a wide range of harnesses, showing great toughness when hardened in the low 50s RC for swords, and hardened up near the 60s for knives needing more edge holding.
Formerly a ball-bearing steel, and as such previously only used by forgers, it’s available in bar stock now. It is similar to 5160 (though it has around 1% carbon vs. 5160 ~.60%), but holds an edge better. It is less tough than 5160. It is used often for hunting knives and other knives where the user is willing to trade off a little of 5160’s toughness for better wear resistance. However, with the continued improvement of 52100 heat treat, this steel is starting to show up in larger knives and showing excellent toughness. A modified 52100 is being used by Jerry Busse in his lower-cost production line, and such high-performance knife luminaries as Ed Fowler strongly favor 52100.
D-2 Steel. An outstanding knife steel, a high-carbon, high chrome tool steel which is often used for the steel cutting dies in every tool and die shop in the U.S.; with 1.5% Carbon, 1% Molybdenum, 12% Chromium and 1% Vanadium, D-2 can be hardened far beyond the favored 60-61 Rc. The first heavy user was Jimmy Lile; the strongest convert has been Bob Dozier. This air hardening steel takes a really good edge, and holds it. This steel has been recently made popular by the great results in the performance of D-2 heat-treated by Dozier. D-2 has a high chrome content of 12.00%; it is called “semi-stainless”, because of the lack of free Chromium in solution. While not as tough as premium carbon steels, it is much tougher than premium stainless steels it is more stain resistant than the carbon steels mentioned above, however. It has excellent wear resistance. D2 is much tougher than the premium stainless steels like ATS-34, but not as tough as many of the other non-stainless steels mentioned here. The combination of great wear resistance, almost-stainlessness, and good toughness make it a great choice for a number of knife styles.
M-2 Steel. M-2 is slightly tougher than D-2. Capable of keeping a tempered edge at high temperatures. However, it is hardly used anymore in factory production knives; CPM M4 is becoming more popular. Custom knife makers still use it for knives intended for fine cutting with very thin edges. It is a High-Speed Steel that works well between 62-66 RC. First used in American Cutlery in kitchen knives and folders by Gerber Blades in the 1960s. 85 Carbon, 6.35 Tungsten, 5.0 Molybdenum, 4.0 Chromium, and 2.0 Vanadium. It can hold its temper even at very high temperatures, and as such is used in industry for high-heat cutting jobs. It is slightly tougher, and is slightly more wear resistant, than D2. However, M2 rusts easily. Benchmade has started using M2
M-4 Knife Steel.
High speed steel, very hard to work but makes a great knife blade that is very difficult to sharpen. Very like M-2 except 1.3 Carbon and 4.0% Vanadium.
Excellent air-hardening tool steel, it is tougher than D2 and M2, with less wear resistance. As air-hardening steel, don’t expect it to be differentially tempered. Its good toughness makes it a frequent choice for combat knives. Chris Reeve and Phil Hartsfield both use A2.
This grade of tool steel air-hardens at a relatively low temperature (approximately the same temperature as oil-hardening grades) and is dimensionally stable. Therefore it is commonly used for dies, forming tools, and gauges that do not require extreme wear resistance but do need high stability.
This grade contains a uniform distribution of graphite particles to increase machinability and provide self-lubricating properties. It is commonly used for gauges, arbors, shears, and punches.
O-1 Tool Steel.
O-1 is a popular forging steel, probably the most popular knife steel of the 20th Century. The first choice of almost all beginning knife makers and still the primary steel for the famous Randall Knives. It has Good wear resistance and edge stability. Relatively tough, but not as much as A2 or 5160. It is most commonly used by Randall Knives, Mad Dog Knives, and many other custom knife makers. O-1 is a simple and basic tool steel that can be hardened to well over 60 RC. With .9% Carbon, 1% Manganese, 5% Chromium and .5% Tungsten. It is a great general purpose tool steel and is very forgiving to the inexperienced knifemaker. This oil-hardening tool steel can be used by both the blacksmith and the stock removal makers.
O-6 Tool Steel.
A much tougher metal than O1. This is one of the absolute best edge retention steels available today.
W1 Tool Steel
is a water hardening tool steel with high carbon content. It is basically a simple high carbon steel with no vanadium and is easily hardened by heating and quenching in water, just as with plain carbon steel alloys. W1 is commonly used for hand operated metal cutting tools, cold heading, embossing taps and reamers as well as cutlery. Carbon-0.70-1.50%, Manganese-0.10-0.40%, Chromium-0.15%, Nickel-0.20%, Vanadium-0.10%, Molybdenum-0.10%, Tungsten-0.50%.
A tool steel that is not stainless. It holds an edge quite well. Not very tough. Has a carbon content of 1.5. Shallow hardening, rather weak, and makes durable knives only if held below 54 HRC. Rusts very easily due to the lack of chrome and vanadium. Only alloying elements are carbon and manganese. Carbon-0.85-1.50%, Manganese-0.10-0.40%, Chromium-0.15%, Nickel-0.20%, Vanadium-0.15-0.35%, Molybdenum-0.10%, Tungsten-0.15%.
0170-6 – 50100-B
These are different designations for the same steel: 0170-6 is the steel maker’s classification; 50100-B is the AISI designation. A good chrome-vanadium steel that is somewhat similar to O1, but much less expensive. The now-defunct Blackjack made several knives from O170-6, and Carbon V may be 0170-6. 50100 are basically 52100 with about 1/3 the chromium of 52100 and the B in 50100-B indicates that the steel has been modified with vanadium, making this a chrome-vanadium steel.
A band saw steel that is very tough and holds an edge well, but rusts easily. It is, like O1, forgiving steel for the forger. If you’re willing to put up with the maintenance, this may be one of the very best steels available for cutlery, especially where toughness is desired. In a poll on the knife makers email list back in the 1990s, when asked what the makers would use for their personal knife, L-6 emerged as the top choice.
CPM 1V Tool Steel
CPM (Crucible Particle Metallurgy) 1V is a proprietary steel, very high toughness, several times higher than A2 with and same level of wear resistance. It is a medium carbon, high alloy tool steel which exhibits high toughness combined with high heat resistance. It is suited for hot or cold applications demanding high impact toughness that also requires moderate wear resistance. Carbon-0.55%, Chromium-4.5%, Vanadium-1.0%, Molybdenum-2.75%, Tungsten-2.15%, Rockwell 56-59,
CPM 3V Tool Steel
CPM 3V is a proprietary steel, very high toughness, less than CPM 1V, but more than A2, and high wear resistance, better than CPM 1V. Used by several custom knives makers and factories, including Jerry Hossom, Reese Weiland. This steel makes a good choice for swords and large knives. It is a high toughness, wear-resistant tool steel made by the Crucible Particle Metallurgy process. It is designed to provide maximum resistance to breakage and chipping in high wear-resistance steel. CPM 3V is intended to be used at 58/60 HRC in applications where chronic breakage and chipping are encountered in other tool steels, but where the wear properties of high alloy steel are required. Carbon-0.80%, Chromium-7.50%, Vanadium-2.75%, Molybdenum-1.30%, Rockwell 58-60.
is designed for use in tooling that encounters severe wear. It’s toughness, or cracking resistance, is higher than other high-wear resistant cold work tool steels permitting it to be used in some applications where CPM 10V, D2 or high-speed steels do not have sufficient resistance to cracking. It is usually limited in hardness to about 56 HRC or lower, and is therefore not intended for applications requiring high compressive strength. Carbon-1.8%, Manganese-0.50%, Chromium-5.25%, Vanadium-9.0%, Molybdenum-1.3%, Rockwell 53-56.
CPM 10V Tool Steel.
CPM 10V is a highly wear-resistant tool steel, toughness comparable with D2 tool steel. Currently used by a few custom knife makers. Phil Wilson uses CPM 10V and other CPM steels. It was the first in the family of high vanadium tool steels made by the Crucible Particle Metallurgy process. Crucible engineers optimized the vanadium content to provide superior wear resistance while maintaining toughness and fabrication characteristics comparable to D2 and M2. Since its introduction in 1978, CPM 10V has become recognized worldwide and sets the standard for highly wear resistant industrial tooling. Carbon-2.45%, Manganese-0.50%, Chromium-5.25%, Vanadium-9.75%, Molybdenum-1.30% Rockwell 58-62.
CPM 15V Tool Steel
CPM 15V is a proprietary, extremely high wear-resistant tool steel, thanks to 14.5% Vanadium content. Found only in custom knives. It is intended for applications requiring exceptional wear resistance. It has more vanadium carbides in its microstructure than CPM 10V and provides more wear resistance and longer tool life in those applications where 10V has proven to be successful. CPM 15V also offers an alternative to solid carbide where carbide fails by fracture or where intricate tool design makes carbide difficult or risky to fabricate.Carbon-3.4%, Manganese-0.5%, Chromium-5.25%, Vanadium-14.5%, Molybdenum-1.3% Rockwell-59-62.
High speed tool steel produced by Crucible using CPM process. M4 has been around long time, lately entering custom and high end production knives. CPM M4 has excellent wear resistance and toughness. Has about 1.42% carbon.
(commonly referred to as S30V) was introduced by Crucible in 2002 in response to knife industry demand for steel with more wear, corrosion resistance and toughness. It has added Vanadium for higher wear resistance and Molybdenum for better pitting resistance. It has superb edge retention because it resists edge chipping. It is on the lower end of the SxxV steels, it has a carbon content of 1.45%. However, S30V is still considered to be a superior choice for knife making. Contents: Carbon 1.45%, Chromium 14%, Molybdenum 2%, Vanadium 4%.
is a martensitic stainless steel designed to offer improved toughness over, CPM S30V. It is also easier to machine and polish than CPM S30V.
CPM-S60V (New Name for the discontinued CPM440V).
Very rich in vanadium. CPM S60V has a carbon content of 2.15%. It was uncommon steel, but both Spyderco and Kershaw Knives offered knives of this steel, Boker still offers folders made from CPM S60V. CPM S90V (formerly CPM T420V), has less chromium than S60V, but has almost twice as much vanadium. S90V’s carbon content is also higher, resting around 2.30%. With 2.15 Carbon, 0.40 Manganese, 17.0 Chromium, 5.50 Vanadium and 0.4% Molybdenum this is steel that would be impressive but when you know that it is a Powder Metal steel with the resulting extreme purity, you know that it has to be a great knife steel.
Has superior edge retention. However, it can be almost impossible to sharpen. Currently custom makers are the only ones using this type of steel. 2.3% Carbon, 14% Chromium, 9% Vanadium and 1% Molybdenum.
Is the latest addition to the SxxV line? It has higher corrosion resistance than S90V and marginally better wear resistance. The additional corrosion resistance while retaining all the benefits of S90V makes this steel extremely desired for kitchen cutlery.
Ultra high carbon stainless. Produced by Crucible Material Corporation using CPM process. Contains 3.25% carbon, 14% chromium and 12% Vanadium and other alloying elements. Exceptionally high wear resistance, making it difficult to process and machine for knife makers. Used only in custom knives.
is identical to 154CM in composition, produced using CPM Process, with all the benefits of the CPM technology.
With 2.15 Carbon, 0.40 Manganese, 17.0 Chromium, 5.50 Vanadium and 0.4% Molybdenum this is steel that would be impressive but when you know that it is a Powder Metal steel with the resulting extreme purity, you know that it has to be a great knife steel. Very expensive and is not at all easy to work.
INFI is currently only used by Jerry Busse. In place of some of the carbon (INFI contains 0.50% carbon), INFI has nitrogen. The result is a non-stainless steel that is nevertheless extremely stain resistant (informally reported at close to D2, or even better), incredibly tough for a high-alloy ingot steel, and with extremely good wear resistance.
Vascowear. A very hard to find steel, with a high vanadium content. It is extremely difficult to work and very wear resistant. Carbon-1.12%, Manganese-0.30%, Chromium-7.75%, Vanadium-2.40%, Molybdenum-2.40%, Tungsten-1.10%
Remember that all steels can rust. But the following steels, by virtue of their > 13% chromium, have much more rust resistance than the above steels. I should point out that there doesn’t appear to be consensus on what percent of chromium is needed for a steel to be considered stainless. In the cutlery industry, the de-facto standard is 13%, but the ASM Metals Handbooks says “greater than 10%”, and other books cite other numbers. It probably makes more sense to measure stainlessness by the amount of free chromium (chromium not tied up in carbides), because free chromium is what forms the chromium oxide on the blade surface that offers stain resistance. The alloying elements have a strong influence on the amount of chromium needed; lower chromium with the right alloying elements can still have “stainless” performance.
Because any particular stainless steel is often heat treated to around the same hardness (i.e., 440C is usually around 57 Rc, ATS-34 is 59-61 Rc, S60V is getting consensus at around 56 Rc, etc.) even by different manufacturers, it’s a bit easier to give a general feeling of the performance you’ll get from different classes of stainless steels, without introducing too many inaccuracies. Please note, though, that the act of grouping differing steels in classes definitely does oversimplify, and some of these steels might more properly fit between the class it’s in, and the following (or previous) one. In addition, better heat treat can move steel up in performance significantly. Last disclaimer: not everyone will agree with the groupings I have here. Whew, all that said, here is a general categorization of stainless steels.
420 and 420J.
represent the low end of stainless steels. They are very stain resistant, and are tough due to being very soft. However, they are also very weak, and not very wear resistant. Generally speaking, expect these steels to lose their edge quickly through abrasion and impaction. They are used in less-expensive knives due to their ease of machining.
440A, 425M, 420HC, 12C27 and 6A
Are the next group. They can be hardened more than the previous group, for better strength, and they are more wear resistant, though wear resistance is just getting to the point of acceptability. 440A and 12C27 are the leaders of this group, with solid heat treat both perform okay. 12C27 is said to be particularly pure and can perform very well when heat treated properly. 6A trails those two steels, though with its vanadium content, can take a razor edge. 425M and 420HC trail the rest.
Gin-1, ATS-55,8A and 440C
Comprise the next group. These steels will usually be stronger than the previous group, and more wear-resistant. Generally speaking, they retain excellent stain resistance properties, though ATS-55 sticks out here as not particularly stain resistant. 8A is also worth a mention, with some vanadium content; it can take an extremely sharp edge very easily, but is also the weakest and least wear-resistant of this group.
ATS34. ATS34 is produced by Hitachi Metals. It is a high-carbon, high-alloy, stainless steel, a Japanese copy of 154-CM, preferred because it is vacuum melted, and 154 is not. These two steels are practically identical in composition. They were introduced into custom knives by Bob Loveless circa 1972. Both are considered premium cutlery steels for folding knives and fixed blades. Carbon 1.05%, Manganese 0.4%, Chromium 14.0%, Molybdenum 4.0%.
VG-10 and S60V
Are the next group up. It’s difficult to make generalisations about ATS-34 and 154-CM — they are in such widespread use that heat treat varies widely. These steels provide a high-end performance benchmark for stainless steels, and hold an edge well, and are tough enough for many uses (though not on par with good non-stainlessness). They aren’t very stain resistant, however. VG-10 can be thought of as being like ATS-34 and 154-CM, but doing just about everything a hair better. It’s a little more stain resistant, tougher, holds an edge a little better. And VG-10 has vanadium in it; it’s fine-grained and takes the best edge of this group. S60V has by far the best wear resistance of the group, though consensus is becoming that it should be left around the same hardness as 440C (56 ish Rc), which means it will be relatively weak compared to ATS-34, 154-CM, and VG-10, and so it will indent and lose its edge quickly when strength is required. S60V is the winner here when pure abrasion resistance is much more important than edge strength.
S90V and S30V
Constitute the next group. BG-42 has better wear resistance than all the previous steels except for S60V. It is tougher than ATS-34, and more stain resistant. It is wear resistant to the point where it can be difficult to sharpen. S90V represents the ultimate in wear resistance in the knife steel discussed so far. Also tougher than ATS-34, and more stain resistant. It can be very difficult to put an edge on. It is difficult enough to machine than it is used almost exclusively in custom knives, not production knives. In your buying decisions, you might want to take into account the difficulty of sharpening these steels. S30V backs off on the wear resistance of S90V, but is significantly tougher and easier to sharpen. It is more wear resistant than BG-42. The jury is still out, but it may end up this week’s ultimate high-end all-around stainless steel, due to high performance coupled with easier machinability and sharpen ability than the other steels in this class.
Okay, On To The Knife Steels In More Detail
Lower carbon content (<.5%) than the 440 series makes this knife steel extremely soft, and it doesn’t hold an edge well. It is used often for diving knives, as it is extremely stain resistant. Also used often for very inexpensive knives. Outside salt water use, it is too soft to be a good choice for a utility knife.
420 modified with more carbon, to be roughly comparable to 440A.
440 A, 440 B and 440C
The carbon content (and hardenability) of this stainless steel goes up in order from A (.75%) to B (.9%) to C (1.2%). 440C is an excellent, high-end stainless steel, usually hardened to around 56-58 Rc, very tough and with good edge-holding at that hardness. 440C was the king of stainless cutlery steels in the 1980s, before ATS-34 took the title in the 1990s. All three resist rust well, with 440A being the most rust resistant and 440C the least. The SOG Seal 2000 is 440A, and Randall uses 440B for their stainless knives. 440C is fairly ubiquitous, and is generally considered a very good general-use stainless, tougher and more stain resistant than ATS-34 but with less edge-holding and weaker. If your knife is marked with just “440”, it is probably the less expensive 440A; if a manufacturer had used the more expensive 440C, he’d want to advertise that. The general feeling is that 440A (and similar steels, see below) is just good enough for everyday use, especially with a good heat treat (we’ve heard good reports on the heat treat of SOG’s 440A blades; don’t know who does the work for them). 440-B is a very solid performer and 440-C is an excellent knife steel.
Both are very similar to 440A. 425M (.5% carbon) is used by Buck knives. 12C27 (.6% carbon) is a Scandinavian steel used often in Finish puukkos and Norwegian knives. 12C27 is said to perform very well when carefully heat treated, due to its high purity. When done right, it may be a slighter better choice than 440A and its ilk.
AUS-6, AUS-8, AUS-10 (Aka 6A 8A 10A)
Japanese stainless steels, roughly comparable in carbon content to 440A (AUS-6, .65% carbon) and 440B (AUS-8, .75% carbon) and 440C (AUS-10, 1.1% carbon). AUS-6 is used by Al Mar, and is a competitor to low-end steels like 420J2. Cold Steel’s use of AUS-8 has made it pretty popular, as heat treated by CS it won’t hold an edge like ATS-34, but is a bit softer (and therefore weaker) and tougher. 8A is a competitor of middle-tier steels like ATS-55 and Gin-1. AUS-10 has roughly the same carbon content as 440C but with slightly less chromium, so it should be a bit less rust resistant but perhaps a bit tougher than 440C. It competes with higher-end steels, like ATS-34 and above. All 3 steels have some vanadium added (which the 440 series lacks), which will improve wear resistance and refines the grain for both good toughness, and the ability to sharpen to a very keen edge. Many people have reported that they are able to get knives using knife steel that include vanadium, like 8A, sharper than they can get non-vanadium steels like ATS-34.
Steel with slightly less carbon, slightly more chromium, and much less moly than ATS-34, it used to be used often by Spyderco in their less-expensive knives. Spyderco has since switched to ATS-55 and 8A, but Benchmade is now using Gin-1 in their less-expensive knives. A very good stainless knife steel, with a bit less wear resistance and strength than ATS-34.
ATS-34 was the hottest high-end stainless in the 1990s. 154-CM is the original American version, but for a long time was not manufactured to the high quality standards knife makers expect, so knife makers switched over to ATS-34. CPM is again making high-quality 154-CM, and some companies seeking to stick with American-made products (like Microtech) are using it. ATS-34 is a Hitachi product that is very similar to 154-CM. Normally hardened to around 60 RC, it holds an edge very well and is tough enough even at that high hardness. Not as rust resistant as the 400 series above. Many custom makers use ATS-34, and Spyderco (in their high-end knives) and Benchmade are among the production companies that use it. Contrary to popular belief, both steels are manufactured through the Argon/Oxygen/Decarburization process (AOD), not vacuum.
Similar to ATS-34, but with the moly removed and some other elements added. This steel is a good cutlery knife steel but a tier behind ATS-34 and its closest competitors (other steels in ATS-55’s class might be Gin-1 and AUS-8). With the molybdenum removed, ATS-55 does not seem to hold an edge quite like ATS-34, and reports are that it’s less rust-resistant. My guess is that with the moly gone, more chromium is tied up in carbides — which mean less free chromium for rust resistance, and softer chromium carbides replacing moly carbides for less wear resistance.
Vanadium containing high-end stainless steel. Due to the vanadium content, VG-10 takes a killer edge, just like other vanadium knife steel like BG-42 and AUS-8. VG-10 is also tougher and more rust-resistant than ATS-34, and seems to hold an edge better.
Vanadium in VG-10 is rather trace amounts, influencing grain refinement, not so much wear resistance. Still, Cobalt and Molybdenum are strong carbide formers; Chromium is also carbide former. Overall, very good steel, but if you are looking specifically for high wear resistance look elsewhere, with alloys having few % V or Nb, etc.
Bob Loveless announced a while back that he’s switching from ATS-34 to this knife steel. Keep an eye out for it; it’s bound to catch on, although the higher cost, limited stock-size availability, and added difficulty of manufacturing are holding BG-42’s popularity back. BG-42 is somewhat similar to ATS-34, with two major differences: It has twice as much manganese as ATS-34, and has 1.2% vanadium (ATS-34 has no vanadium), so look for significantly better edge-holding than ATS-34. The addition of vanadium and the clean manufacturing process (VIM/VAR) also gives BG-42 better toughness than ATS-34. Chris Reeve has switched from ATS-34 to BG-42 in his Sebenzas.
S60V (CPM T440V) – S90V (CPM T420V)
Two steels that hold an edge superbly, world class type edge holding, but it can be difficult to get the edge there in the first place. These steels are made with Crucible’s particle metallurgy process, and that process allows these steels to be packed with more alloying elements than traditional steel manufacturing methods would allow. Both steels are very high in vanadium, which accounts for their incredible wear resistance. Spyderco offers at least one model in CPM S60V. Spyderco, one major user of S60V, has cut back hardness down to 55-56Rc, in order to keep toughness acceptable, but that sacrifices strength so there is a tradeoff. S90V is CPM’s follow-on to 440V, and with less chromium and almost double the vanadium, is more wear-resistant and tougher than S60V — and, in fact, is probably more wear-resistant than any other stainless steel used in the cutlery industry. As such, S90V is in the running with steels like BG-42 as among the best general-purpose stainless steels; however, S90V is even more expensive and difficult to work than BG-42, so it’s strictly in the realm of custom makers currently..
The newest stainless steels from Crucible are purpose-designed as a cutlery steel. This steel gives A2-class toughness and almost-S90V class wear resistance, at reasonable hardness (~59-60 RC). This mix of attributes is making S30V one of the hottest stainless steels going, with makes such as Chris Reeve switching from BG-42 to S30V. Will this be the new king of general-purpose stainless cutlery steels? We’ll know over the next couple of years.
The section about S30V was written when it was just appearing on the market. By now it is not new, was well tested and is used in knives of all varieties. Toughness is nowhere near that of A2 steel, and wear resistance, while being quite high, still not on S90V levels either. Very decent steel never the less, just didn’t live up to all the hype surrounding its development.
400 Series Stainless
Before Cold Steel switched to AUS-8, many of their stainless products were marketed as being of “400 Series Stainless”. Other knife companies are beginning to use the same term. What exactly *is* 400 Series Stainless? I always imagined it was 440-A, but there’s nothing to keep a company from using any 4xx steel, like 420 or 425M, and calling it 400 Series Stainless.
Damascus Knife Steel
are made by forge-welding two or more different metals (usually steels). The billets are heated and welded; to get an idea of the process. The Damascus is then acid-etched. The different metals etch at different rates, and depth and colour contrast are revealed.
Damascus can be made with performance and/or aesthetic objectives in mind. Aesthetically, the choice of materials is important. One shiny steel and one darker steel etch out to show the most striking pattern. If the maker is going more for beauty than performance, he might even go with nickel, which is bright but does not perform as well as steel for cutlery applications. The other factor affecting beauty is of course the welding pattern. Many patterns of Damascus are available today, from random to star to ladder, and a whole lot more.
The Following Knife Steel Will Provide Bright Lines:
• L-6 and 15N20 (the Swedish version of L-6) — nickel content
• O1 — chromium content
• ASTM 203 E — nickel content
The Following Knife Steel Will Provide Dark Lines:
Non-Steels Used For Cutlery
Talonite,Stellite, 6K, Boye Dendritic Cobalt
These cobalt alloys have incredible wear resistance, and are practically corrosion resistant. Stellite 6K has been around for years, but was expensive and very difficult to work, and so is only rarely seen. Talonite is easier to work, and as a result has been gaining in popularity, especially among web-based knife buyers. David Boye uses his casting process to manufacture Boye Dendritic Cobalt. This material is tough and has great wear resistance, but is relatively weak.
Newer titanium alloys can be hardened near 50 RC, and at that hardness seem to take something approaching a useful edge. It is extremely rust-resistant, and is non-magnetic. Popular as expensive dive knives these days, because the SEALs use it as their knife when working around magnetic-detonated mines. Mission knives’ uses titanium. Tygrys makes a knife with a steel edge sandwiched by titanium.
Numerous knives have been offered with ceramic blades. Usually, those blades are very very brittle, and cannot be sharpened by the user; however, they hold an edge well. Boker and Kyocera make knives from this type of ceramic. Kevin McClung came out with a ceramic composite knife blade that much tougher than the previous ceramics, tough enough to actually be useful as a knife blade for most jobs. It is also sharpened by the user, and holds an edge incredibly well.
Sources For This Article
- AISI American Iron & Steel Institute
- SAE Society Of Automotive Engineers
- Australian Knife Club research & development, including my 35 years experience as a Tradesman in Fitting and Turning and Toolmaking
- Statistical data and steel definition from machinery’s handbook
- With the kind permission of zknives definitions graphs and statistical data used to compile this document
- Wikipedia for general definitions
- General consultation With selected knife makers
- dckknives for the knife templates