Anthropologists tell us that it was Homo sapiens’ early Hominid ancestors ability to use tools that enabled them to not only survive, but to thrive in an environment filled with large predatory animals. They were able to survive long enough to eventually evolve into modern humans who then conquered the entire animal kingdom.
However, stone age technology was only able to propel man so far, therefore forced to evolve, man eventually progressed out of the stone age, into the bronze age and then into the iron age. Iron is one of the most abundant minerals available on Earth. Its discovery and the discovery of the process of how to smelt the ore and cast (or forge) the metal literally changed our destiny.
Discovery of steel
Even though the discovery of iron changed the course of human history, there was still one more vital discovery that smiths had to make before our historical play could continue to its present point. That discovery was that by infusing the element Iron with the element Carbon, a compound was created that was lighter and yet, stronger than Iron.
Since then, the science of Metallurgy has developed into a very exacting science. This has enabled modern steel manufacturers to produce some new, proprietary, blade steels with performance levels that, in some cases, are so phenomenal that they would literally seem like Excalibur to the those first steel smiths!
So, if you have ever wondered how iron differs from steel, what the different types of modern blade steels are and, why some blade steels seem to perform so much better than others, then read on for the answers to all of your questions about the best knife steel!
Iron vs. Steel
First off, what is the difference between iron and steel? Steel is defined as iron that contains at least 0.02% Carbon. But, it should be noted that iron can only absorb a maximum of 0.80% Carbon, any Carbon count over this amount serves to create carbides.
This leads to our next question, how exactly do you get carbon into iron? Let's go back to how iron was discovered in the first place. The first bladesmiths discovered that by heating iron in a coal forge they could get the metal significantly hotter than using a charcoal fire. By heating the metal to a sufficiently high temperature, the extreme heat allows carbon atoms from the burning coal to slip in between the iron atoms.
It's important to note that the two atoms do not bond, once the iron has become infused with carbon the resulting steel must be cooled (called "quenching") quickly. This process traps the carbon atoms inside of the iron atom matrix otherwise they will escape (called "annealing").
However, while coal forging was the original process for converting iron to steel, modern blade steels are generally made by using electric furnaces. They can melt the metal and carbon and other elements can be added in precise quantities to produce proprietary blade steels.
Plain Carbon Steel vs. Stainless Steel
Knife steel is far more than simply pieces of iron infused with a certain amount of carbon. Because there are many different types of blade steels there are different levels of classifications.
Blade steel classifications
They are first classified by their carbon content. Low alloy steels are classified as any steels having less that .30 percent carbon. Medium alloy steels are those that have .30 to .45 percent carbon. High alloy steels which have .45 to .75 percent carbon. Lastly, very high carbon alloys have .75 to 1.5 percent carbon.
Blade steels are further classified by their chromium content, which is added to the steel to increase its corrosion resistance. They are classified as either plain carbon steels or stainless steels.
According to the Standard of Automotive Engineers steel grading system, a blade steel must contain at least 10.5 percent chromium in order to be classified as a stainless steel. However, the generally accepted definition of a stainless steel is one that contains a minimum of 12 percent chromium.
Blade Steel Grain Structure and How it Affects Performance
When steel is viewed at a high magnification, it becomes obvious that it has a grain structure similar to grains of sand. The smaller the crystals are, the tougher and stronger the steel with be, and the better it will hold an edge. So while adding chromium to steel increases corrosion resistance, it also increases the size of its crystals.
As a general rule, plain carbon steels commonly have a smaller grain structure than those of stainless steel because they lack the chromium carbides. This makes this tougher and easier to sharpen, allowing them to take a finer edge than stainless. Only downside is they will not hold an edge as long and are far more prone to corrosion due to their lack of chromium.
All stainless steels contain at least 10.5% chromium, which combines with the carbon to form corrosion resistant chromium carbides. At the same time, the chromium carbides also increase the grain size, and this is why metallurgists often add additional elements like manganese, vanadium or tungsten to the steel to increase both its hardness and its strength.
Stainless steels are stronger than plain steels, but they are not as tough. And while they may hold an edge better than a plain carbon steel, they will not take quite as fine an edge. But, of course, stainless steels do a far better job of resisting corrosion than plain carbon steels do.
Each type of steel has both its advantages and disadvantages that may make it better suited for one job over others. As a result, you'll notice most manufactures will choose a plain carbon steel for making large, heavy duty knives such as camping and survival knives and even machetes. They'll choose stainless steels for edc knives and hunting knives.
Blade Steel Elements
As an overview, when carbon is combined with iron and both have been heated to a sufficient temperature, carbon and iron become infused together to create the metal we call steel. But, you should also be aware that there are several other elements that modern metallurgists also combine with carbon to create proprietary blade steel alloys with different specific properties.
The rockwell hardness scale
The Rockwell scale is a hardness scale based upon the indentation hardness of a material. The Rockwell test determines the hardness of a material by measuring the depth to which an indenter penetrates under a given load compared to the penetration made by a preload.
Because penetrators made from different materials and, penetrators with different dimensions are used to test different materials, different scales exist. Scales such as HRA, HRB, HRC and so on. The Rockwell Hardness C scale is used to test blade steels, as a result all blade steel Rockwell Hardness designation are expressed as a number followed by the capital letter C.
Almost all blade steels have a Rockwell Hardness between 50 HRC and 65 HRC. Any steel with a designation between 50 - 53 HRC would be considered soft. Any steel with a designation between 54 - 57 HRC would be considered medium to hard. And any steel with a designation of 58 - 62 HRC would be a hard blade steel.
The harder the blade steel, the better it will hold an edge, but it will be more difficult to sharpen and more prone to break under stress. On the other hand, the softer blade steel will lack in edge retention but be less prone to break under stress. One advantage of softer steels is they will be much easier to sharpen, if you are new to sharpening knives a softer steel is a good steel to practice with.
The hardness of a blade steel is an important distinction when choosing a steel for your intended purpose. Large heavy duty knives generally need to be impact resistant and easy to sharpen, whereas hunting knives generally need to be designed to hold an edge exceptionally well, even though they will be more difficult to sharpen.
Pocket knives are best with blades that are in between hard and soft, its very important you pay attention to the Rockwell Hardness for the blade on any knife you choose for a specific purpose. Knowing this information will help you choose the right blade steel for the job at hand.
Blade steel properties
Why does the type of blade steel matter?
Now that you have an understanding of the differences between plain carbon blade steels and stainless steels, the next step is to choose the proper steel for your intended purpose.
key points to remember when choosing a blade steel.
Which steel for your purpose
Armed with the knowledge above picking a blade steel will no longer be a guessing game. For instance, large knives and/or long knives such as camp knives and machetes are often used for chopping.
These types of knives need to be made from tough blade steels such as 01, 1095, 5160 or 65Mn. Tough blades steels like these resist micro-chipping, cracking and breaking.
Whereas, harder blade steels like 440C, ATS34, 154CM and CPM S30V resist edge rolling and have a high degree of wear resistance. Knives made from hard steels will hold their edge over an extended period of use, but they are also more prone to break under stress.
Knives designed specifically for hunting are seldom subjected to impact or lateral stress, so making them from a hard blade steel provides the user with longer edge retention.
On the other hand, pocket knives are subjected to a wide range of uses and they are often carried in pants pockets exposing them to perspiration. Therefore, many pocket knives are made from medium to hard steels because they do a better job of resisting lateral stress and corrosion, while still remaining relatively easy to sharpen.
Proprietary steels are expensive
Choosing a blade steel depending on your intended purpose is one important factor, but another factor is the expense of such tool.
Proprietary high end blade steels certainly provide superior performance, but they also demand a premium price tag. So by knowing what your steel needs are in a knife blade, you can easily match your blade steel choice with your intended purpose within any given price range.
A description of popular knife blade steels
With everything we have covered your should be able to recognize some of the properties in these steels and identify how they impact performance on a blade.
American powder-made stainless steel developed by custom bladesmith Chris Reeves and Crucible Materials Corporation. CPM S30V is best known for its wear and corrosion resistance and is considered to be one the best blade steels ever made.
It's chemistry promotes the formation and even distribution of vanadium carbides which are harder and more effective at cutting than chromium carbides. Vanadium carbides give the steel a very refined grain structure which further contributes to the sharpness and toughness of the edge.
An American made, but less expensive version of CPM S30V. D2 is an outstanding high carbon, semi stainless steel tool steel that is used for steel cutting dies in nearly every tool and die shop in the US.
It's a popular choice because it can be hardened far beyond the favored 60-61 HRC. Consequently, this air hardening steel takes an excellent edge and holds it exceptionally well.
Although the first bladesmith to use this steel was Jimmy Lile, the strongest convert has been Bob Dozier who has made this steel popular by mastering the heat treating process.
The original 154-CM is a proprietary, American-made, high-carbon, high-alloy, space-age, stainless steel that was first used for knives in the early 1970's.
At that time it was a vacuum-melted steel, but after a few years the quality declined because the manufacturer ceased to vacuum-melt the steel. Eventually, bladesmiths moved away from 154-CM to the Japanese equivalent steel ATS-34.
However, today, CPM 154-CM is made by short-run blade steel manufacturer Crucible Industries and the quality has been restored.
American-made stainless steel that, until the discovery of 154 CM in the early 1970’s, was the single most popular, high-carbon, stainless steel among custom bladesmiths.
First used by Gil Hibben around 1966, 440C is a great steel when properly heat-treated. Its Molybdenum content allows it to take a fine edge, while its high carbon content lets it to do a good job of holding it.
Yet, its Manganese content also causes it to do an exceptionally good job of withstanding impact for a stainless steel and, its relatively high Chromium content causes it to be highly resistant to corrosion. It does a good job for not only hunting knives, but is also favored for large, heavy duty knives.
0.95 - 1.20% Carbon
16 - 18% Chromium
420HC is a somewhat less expensive American-made stainless alternative to 440C. While it is similar in composition to 440C, it neither withstands impact as well nor, does it take and hold as fine an edge and, it is not as corrosion resistant.
0.4 - 0.50% Carbon
12 - 14% Chromium
420J2 is an inexpensive American-made stainless steel typically reserved for very inexpensive production knives. It's an adequate blade steel when you need a knife, but it does not take a very fine edge nor does it hold it well. It also isn't nearly as resistant to corrosion as 440C.
12 - 14% Chromium
VG-10 is a proprietary Japanese stainless steel that was developed specifically for use in high end Japanese chef’s knives. Consequently, VG-10 stands for V Gold 10 ("gold" meaning high quality), or sometimes V-Kin-10 (kin means "gold" in Japanese) because this steel is of such high quality. It's considered to be the gold standard Japanese blade steel.
Due to its composition, which results in a very fine grain structure, it's able to take a very fine edge and, its high degree of abrasion resistance enable it to do an excellent job of holding it.
But, it is generally a more expensive steel, so sometimes it is laminated to a tougher stainless steel such as VG-1. so that the VG-10 forms the core of the laminate (called San Mai construction).
A high-carbon, high-alloy, Japanese copy of CPM 154-CM except for a 0.1% difference in Manganese content, ATS-34 is vacuum-melted steel that is widely considered to be the second best blade steel available after CPM-S30V.
AUS-10 is a tough, highly corrosion resistant, stainless steel that is commonly used in knives that will see hard use.
AUS-8, similar to AUS-10 is a tough, highly corrosion resistant, stainless steel that is commonly used in knives that will see hard use.
VG-1 is a less expensive Japanese stainless steel somewhat similar to 420HC but which is mostly used by Cold Steel on knives that require a tough blade steel composition. It has a Carbon content between 0.95-1.05%, a Chromium content between 13.0-15.0%, a Molybdenum content between 0.20-0.40% and, it contains less than 0.25% Nickel. Plus, it has a typical hardness of 58-61 HRC
8Cr13MoV is a Chinese equivalent to AUS8 and thus, it is a relatively tough stainless steel that holds an edge relatively well. Many budget pocket knives use this steel, some great examples would be the Spyderco Tenacious and the Kershaw Cryo. It contains 0.80% Carbon, 13% Chromium, 0.40% Manganese, 0.20% Nickel, 0.5% Molybdenum, and 0.10% Vanadium and, it has a typical hardness of 58-59 HRC.
Sandvik 12C27 is a Swedish stainless steel and is Sandvik's most well-rounded knife steel. It provides excellent edge performance allowing razor sharpness, high hardness, exceptional toughness and good corrosion resistance. It contains 0.60% Carbon, 13.5% Chromium and, 0.40% Manganese, and, it has a typical hardness of 57-59 HRC.
Bohler M390 Microclean
This is a high end, third generation, Austrian-made, powder metallurgy, stainless steel with a very small grain size that is equivalent to a super version of CPM S30V.
In fact, it was developed specifically for knife blades requiring good corrosion resistance and a very high degree of hardness for excellent wear resistance.
Uddeholm Elmax superclean
A third generation Austrian, powder-metal stainless steel that is noted for its fine carbide distribution with extremely low inclusion content. Its an excellent balance between corrosion resistance and edge retention.
It contains 1.70% Carbon, 18% Chromium, 1.0% Molybdenum, 3% Vanadium, and 0.30% Manganese and, it has a typical hardness of 57-59 HRC and 60-62 HRC with deep freeze. For maximum toughness, it should be hardened to 57-59 HRC and, for maximum wear resistance, it should be hardened to 60-62 HRC.
Is a conventionally made Austrian stainless steel that is Bohler’s best value in a corrosion resistant blade steel with excellent edge holding capabilities. In fact, it will take as fine an edge as VG-10 and it will hold an edge as well as both ATS-34 or VG-10.
It contains 1.08% Carbon, 17.3% Chromium, 1.1% Molybdenum, 0.1% Vanadium, 1.50% Cobalt, 0.4% Manganese and, 0.40% Silicone and has a typical hardness of 58-60 HRC for maximum toughness and, 60-62 HRC with cryogenic treatment for maximum wear resistance.
An Austrian-made, conventionally produced, 440C stainless steel equivalent with a high degree of hardness and wear resistance. It has good corrosion resistance in the hardened and tempered condition. It contains 1.05% Carbon, 17% Chromium, 0.50% Molybdenum, 0.40% Manganese, and 0.40% Silicone and has a typical hardness of 57-60 HRC.
An inexpensive, fine-grained, German, stainless steel that is made by Thyssen Krupp, and is commonly referred to as “Solingen Steel”. Also, it is a medium carbon stainless steel commonly used for low-end factory knives where the blades are fine blanked because, if the carbon content were higher, the blade blanking dies would wear too fast.
However, the balance of carbon and chromium does give it a high degree of corrosion resistance and also impressive physical characteristics of strength and wear resistance.
Non-Stainless blade steels
Now let's take a quick look at some of the non-stainless blade steels often used. These steels with offer highest wear and impact resistance. They are often used wear chopping and hard use blades are required, such as axes and machetes.
An American-made, non-stainless, steel designed to provide maximum resistance to breakage and chipping in a highly wear-resistant metal.
It has an impact resistance greater than that of A-2, D-2, Cru-Wear or CPM-M4 and other shock resistance metals while providing excellent wear resistance and a high degree of hardness.
It contains 0.80% Carbon, 7.50% Chromium, 1.30% Molybdenum, and 2.75% Vanadium and, it has a typical hardness of 58-60 HRC.
An American-made, non-stainless, electric-furnace melted, oil-hardened, non-shrinking, general-purpose, tool steel that is popular with custom knife makers.
It's a highly versatile steel since it can be used for stock removal as well as forged knives and is often utilized for tomahawks and axes as well. With a proper heat treatment, O-1 will take and hold a very fine edge while remaining remarkably tough and durable.
O-1 is an ideal steel for edged weapons and tools because it is known for its ability to be differentially heat treated. It contains 0.95 percent Carbon, 0.6 percent Chromium, 0.6 percent Tungsten, 0.1 percent Vanadium, and. 1.1 percent Manganese and it has typical hardness of 53-54 HRC.
An SAE grade plain carbon steel commonly used for tools. The carbon content and lean alloy make it a shallow hardening steel depending on carbon content and, this combination of factors makes this one of the toughest steels available.
When quenched, it produces a near saturated lathe Martensite with no excess carbides; avoiding the brittleness associated with higher carbon materials. This steel is particularly well suited to applications where strength and impact resistance are valued above all other considerations and will produce blades of nearly legendary toughness. It contains 0.90% 1.03% Carbon and 0.30% - 0.50% Manganese and, it has a typical hardness of 56-58 HRC.
SK-5 is the Japanese equivalent of American 1080 and is a high carbon steel that combines a mixture of carbon rich Martensite with some small undissolved carbides. The excess carbides increase abrasion resistance and allow the steel to achieve an ideal balance of very good blade toughness with superior edge holding ability.
Due to these characteristics, this grade of steel has been traditionally used for making hand tools and has stood the test of time and use over many years in many countries. Last, it contains 0.80%-0.90% Carbon, 0.15% - 0.50% Manganese, 0.15% - 0.35% Silicone.
Resources & Further Reading
If you wish to dive deeper into the best blade steels, below are some of the best resources on the internet for this topic. I especially like A.G. Russell's charts and refer to them often.