Knife Steels, Stainless, Carbon, and Tool Steels
High Carbon, Stainless, Tool Steel, CPM Steels
Hint: They're not all the same!
The type of steel used to make a knife greatly impacts its performance. Some steels are easier to sharpen, while others are tougher, harder, or hold an edge better. In my shop, I select steels based on their potential hardness, ease of sharpening, toughness, availability, and affordability (with a few exceptions). However, the final result also depends on the heat treatment, profile, bevel grind, and sharpening technique. Keep in mind that no steel is perfect in every category, with some excelling in strength, edge retention, stain resistance, or sharpenability.
I may add more options in the future, but at a slow pace. If your favorite steel isn't listed, feel free to reach out and we can work something out together.
Learn Heat Treating Terms HERE!
For many years, A2 steel has been a popular choice for tool, die, and knife makers. The "A" in the name indicates that it is an "air hardening" steel. By heating A2 to a high enough temperature and cooling it in still air, it can achieve full hardness. Chromium, which is present in A2 at a level of 5%, increases the steel's "hardenability." Although A2 does not contain enough Chromium to be classified as "stainless," it is still suitable for air hardening. A2 steel contains 1% carbon, 1% Molybdenum, and .4% Vanadium. The addition of Molybdenum increases hardenability, while Vanadium helps to keep the grain structure small. The 5% Chromium content increases edge retention and hardenability compared to regular carbon steels. A2 steel can achieve a hardness level of more than 64Rc when quenched, and custom knives are usually tempered to 58-60Rc. A slight increase in hardness to around 62Rc can enhance edge retention with no significant loss of toughness. To enhance the hardness and strength of A2, the steel is soaked in a liquid nitrogen bath at cryo temperature (-320F) immediately after austenitization and before tempering cycles begin. A2 steel is available in Black Mountain at Keith Nix Knives.
At Keith Nix Knives, I have opted for AEB-L steel as our "house stainless" due to its remarkable durability, exceptional toughness, good stain resistance, and solid edge retention. Over time, stainless steel chef's knives have garnered a negative reputation, particularly in the 50s and 60s, for being weak, soft, and incapable of holding an edge. This, however, can be attributed to the influx of factory knives made from the 420 series stainless steel, which only contained 0.3% carbon, making it unsuitable for high-quality knives. Nevertheless, it was easy to shape, machine, and polish, and it was also highly resistant to staining.
Around a century ago, Uddeholm from Sweden began developing a new stainless steel specifically for razor blades. This steel was required to be exceptionally hard (62 HRc or above), have the ability to be stamped to shape with dies (as previously mentioned), and feature a fine carbide structure that was suitable for razors. The first iteration was AEB, but the chromium carbides were too large and resulted in an unsuitable toothy edge for razor blades. Later, AEB-L was developed, which was the perfect balance of all the necessary attributes, such as fine blanking, edge retention, hardness, ultra-fine carbides, and stain resistance. AEB-L steel is available in Black Mountain at Keith Nix Knives.
From Devin Thomas at devinthomas.com:
"Few know what AEB-L steel is, and those that do, only have heard that it is similar to 440B or 440A. The only similarity between AEB-L and 440B or 440A is the amount of carbon. The fact that AEB-L has only 12.8% chromium by weight compared to the 16-17% in 440A and 440B makes the steels quite different. AEB-L is more similar to a stainless 52100 than 440A. A copy of AEB-L called 13C26 is made by Sandvik.
AEB-L naturally forms what is called the K2 carbide, the harder of the two chromium carbides, compared to the K1 carbide, which is formed in steels such as 440C. The K2 carbide is about 79 on the Rockwell C scale, compared to 72 for the K1 carbide. Through proper heat treatment, AEB-L has fine, evenly distributed K2 carbides. AEB-L lies almost perfectly on what is called the "Carbon Saturation Line," which means that all of the carbides formed are precipitated carbides, not primary carbides like are formed in 440C, and there is more carbon and a similar amount of Chromium in solution as compared to 440C. Primary carbides are very large. So, through a balanced composition, AEB-L has excellent toughness, edge retention, workability, ease of sharpening, and ease of polishing."
D2 tool steel is a type of air-hardening tool or die steel that is commonly utilized in the creation of cold-work stamping dies for metalwork. This material boasts very good hardness, superb abrasion resistance, and impressive edge retention, as well as SOME degree of stain resistance. To optimize its sharpness, diamond stones are recommended due to D2's high abrasion resistance. Cryogenic treatment can further enhance D2's performance, resulting in increased hardness, slightly better edge retention, and greater abrasion resistance. Although not particularly tough, D2 is well-suited for use in smaller, more durable blades. D2 steel is available in Black Mountain at Keith Nix Knives.
52100 is renowned for its high potential hardness, making it an ideal choice for ball bearings and bearing races. This high-carbon, low-alloy steel is also known for its exceptional toughness, fine grain structure, balance of properties, and ability to take an extremely keen edge. Developed in the early 1900s, 52100 contains about 1% carbon, which contributes to its high hardness. The addition of 1.5% chromium enhances hardenability and decreases grain size within the steel, resulting in better toughness and edge retention. For many years, this steel has been used by bladesmiths to create high-quality knives, typically from round stock or salvaged bearings and races. Nowadays, custom knifemakers can find flat bars of 52100 that are suitable for stock removal.
52100 is a very tough steel due to the small, evenly distributed carbide throughout the steel matrix. In extensive toughness testing, 52100 comes out on top of O1, 1095, 440C, D2, A2, and many other knife steels held in high regard in the knifemaking world. Its high attainable hardness makes 52100 a great choice when corrosion isn't an issue. I highly recommend it for hard-use Outdoor Knives or in the kitchen when the chef prefers a non-stainless option for a slightly keener edge. 52100 steel is available in Black Mountain at Keith Nix Knives. To get your custom knife in 52100 steel, visit the Shop NOW.
If you're a chef or professional cook who prefers carbon steel knives, you may want to consider 26C3 steel. This non-stainless steel is commonly known as 26C3 in the US and 1.2002 in Germany. Uddeholmstrip produces it for use in razor and scalpel blades due to its exceptionally fine grain and carbide microstructure, making it highly pure and capable of extreme hardness. It can reach above 67HRc as-quenched while maintaining good toughness.
Compared to other mainstream steels like 1095, O1, M2, A2, and PSF27, 26C3 holds up well in terms of toughness. It can hold a keen edge and resist chips, even at high hardness. This steel is similar in composition to Hitachi White #1, a well-known Japanese blade steel.
However, it's important to remember that 26C3 is not stainless and requires proper maintenance to prevent rust and pitting. With proper care, it can develop a beautiful patina over time. These high hardness carbon steel kitchen knives are tough and durable, making them a great choice for chefs who demand the best from their knives. Refer to "How to Care For Custom Knives" to learn more about the care of carbon steel knives. So if you're looking for a really hard, very fine-grained custom chef's knife, we have the steel for you at Keith Nix Knives! 26C3 steel is available in Black Mountain at Keith Nix Knives. Give me a call today at 828-337-7836...
CPM MagnaCut steel is a recent development by Metallurgist and Knife Steel Nerd Author, Dr. Larrin Thomas. It is manufactured by Crucible and specifically designed to be used as a knife steel. This stainless steel has exceptional wear and stain resistance, as well as high hardness and toughness. It can maintain excellent toughness while achieving a working hardness in the range of 63-64HRc. The addition of Vanadium and Niobium helps to keep the grain and carbide size very small, thus increasing toughness. VAnadium and Niobium also form tiny and very hard carbides, resulting in a significant increase in edge retention. Although it is much more expensive than conventionally produced steels, CPM MagnaCut provides an outstanding balance of properties that cannot be found in any other stainless steel composition. CPM Magnacut steel is available in Black Mountain at Keith Nix Knives.
CPM M4 tool steel is a remarkable high-speed steel that boasts of exceptional edge retention and good toughness. Its composition includes 4% chromium, 4% vanadium, 5.25% molybdenum, and 5.5% tungsten. The high carbon content in the steel enhances its hardness and facilitates the formation of carbides from the aforementioned metals. The addition of 4% chromium improves hardenability, tensile strength, and edge retention. 4% vanadium ensures that CPM M4 has a fine grain size, and it increases wear resistance and edge retention with extremely hard, fine carbides. The high 5.25% molybdenum content enhances the steel's strength and machinability. Tungsten, on the other hand, enhances wear and corrosion resistance. Thanks to CPM technology, this steel has a fine grain and carbides that make it exhibit excellent toughness. This steel is a top-quality material to use, especially when stain resistance is not a concern. CPM M4 steel is available in Black Mountain at Keith Nix Knives.
Learn more about CPM M4 HERE!
80CRV2 is a low alloy carbon steel, with small amounts of chromium and vanadium added. Similar to the old 1095 Cro-Van used by K-Bar years ago, there's just enough of these elements to provide specific properties during and after heat treating.
1- The .8% Chromium increases "hardenability", making the steel easier to harden without using a water quench. Water severely stresses blades, while a fast engineered oil is far less stressful. The Cr addition also helps prevent grain growth during heat treatment of the blades.
2- Vanadium is added at .2%. Not enough to affect edge retention, but enough vanadium carbides to pin grain boundaries and hinder grain growth.
80CRV2 is an excellent choice for hard use blades, with toughness far better than 1095, O-1, or D2, especially at higher hardness. It is easy to sharpen though it has low edge retention. Being a carbon steel it is quite prone to rust staining, but folks who prefer carbon steels know that.
What is Cryogenic Treatment?
And What Does It DO??
In simple terms, Cryogenic Treatment is a process where a knife is further cooled down to -320F after being quenched to room temperature from its austenitizing temperature according to specific standards and protocols for that steel. This extended cooling process helps to convert the retained softer phase Austenite to harder and stronger Martensite, resulting in improved knife steels. To achieve this, we use liquid nitrogen for an hour or even overnight after the quench. Following this, the tempering cycles are performed as usual. At Keith Nix Knives, we ensure that your custom knives receive the very best heat treatment possible, and cryogenic treatment is a proven method to enhance their performance. Learn more about Cryogenic Treatment of knife steels HERE.
Dr Larrin Thomas wrote a three part article on his blog "Knife Steel Nerds" about cryogenic temperatures and the effect on knife steels. If you're a knife steel nerd like me, click on the link!
Dr Larrin Thomas explains cryo treatment of knife steels