Knife steel is a critical component of the custom knife. Making a fine homemade knife is a work of patience, and a dedication to precision craftsmanship. A custom knife maker must understand the science of metallurgy when choosing an appropriate knife steel.
To rust or not to rust, that is the question. Actually, that is only one of the questions. To maintain a great edge, or not to maintain a great edge is another important question! Many custom knife makers are finding middle ground for those two questions.
High carbon and stainless steels are both acceptable if properly alloyed. The high carbon steels are typically the steels that are forged. They can be differentially tempered. This property gives the knife maker more options. He can better control the hardness of the cutting edge, and still have a tough knife with a springy back.
Let’s consider first, some of the more common carbon knife steel available.
1095 is the most popular steel for knives. It is a simple steel consisting of.95% carbon, and.4% manganese. Other 10 series steels are used for knife making such as 1084, 1070, 1060, and 1050 etc. Each of these steels are decreasing in carbon content, and thus are also decreasing in wear resistance. At the same time, as the carbon content goes down the toughness goes up. As such, some of the lower carbon content designations are more commonly used for swords.
O-1 steel is another high carbon steel which gives razor sharp edges but dulls quicker than A2 Steel. O-1, like A2 has a 1% carbon content It has 1.35% manganese,.5% chromium,.35% silicon, and.5% tungsten. O-1 steel is more forgiving to those who are not as accomplished in getting a decent edge. In summary, it is easier/faster to hone to a razor sharp edge than some of the other choices, but does not stand up to abuse as well. 0-1 is very popular with forgers and bladesmiths. It is tough, although not as tough as 5160.
L-6 is very similar to O-1. It is basically band saw steel. It is possibly the very best steel for a knife if maintenance is not an issue. It rusts very easily, but holds an edge very well. It is also very tough. It is a favorite of forgers.
W-2 is reasonably tough and holds an edge well because of its.25% vanadium. It also has.25% manganese, and silicon. It is not as common or popular.
A2 steel is almost a stainless steel. At (5%) it does not have quite enough chromium. It has 1% carbon,.6% Manganese, 1% molybdenum, and.2% Vanadium. It is not prone to rust. A2 steel is popular for combat knives because of its toughness. The toughness of the edge of the A2 steel is improved by cryogenically treating the blades at -320 degrees Fahrenheit. A2 steel is much harder than 0-1 carbon steel and although more difficult to sharpen, it keeps an edge longer. It performs best somewhere between 30 and 35 degrees. The problem with A2 steel is that it tends to fracture more easily when the bevel is ground less than 30 degrees. A2 is tougher than D2 and M2, but has less wear resistance.
M2 Steel is a fine-grained molybdenum/tungsten high-speed tool steel. It has.85% carbon,.25% manganese, 4.2% chromium,.30% silicon, 5% molybdenum, 6.35% tungsten, and 1.9% vanadium. It is an excellent choice for high temperature applications. For example, the annealing temperature of M2 steel is approximately 1000° F. It is slightly tougher and more wear resistant than D2, however, M2 rusts more easily.
“D” series steels are classed as cold work tool steels. D2 steel is a premium tool steel. With 1.5% carbon content It is better at holding an edge than less exotic stainless steels. D2 has a fairly high chromium content (11.5%) and is sometimes referred to as a “semi-stainless”. It is a well respected, air hardened, high carbon, high chromium tool steel. It has 1% molybdenum, and.9% vanadium. It possesses extremely high wear resistance properties. D2 steel is one of the toughest knife blades you can get, and is a favorite of the best custom knife makers. Anyone who has ever used a good D2 steel blade in the field, raves about the steels cutting ability, durability, and edge holding properties. Simply put, D2 steel can produce one of the best blade stocks available for a working knife.
5160 steel is a common spring steel. It is basically 1060 with 1% of chromium added to make it deep hardening. It is used in swords, axes or other high-impact tools. 5160 Steel is popular now for a variety of knife styles, but is usually used for bigger blades that need more toughness. It is quick and easy to sharpen, and, when resistance to lateral forces comes into play, 5160 is a champion.
50100-B is the AISI designation of the same steel as 0170-6. The B designates vanadium has been added. This steel is a good chrome-vanadium alloy that is similar in properties to 0-1, but it is much less expensive. It is essentially 52100 with 1/3 less chromium.
52100 is often compared to 5160. It has a little more carbon content than 5160, and thus holds an edge better. It isn’t as tough though. The tradeoff is in wear resistance. Many hunting knives are now being made from this steel.
Now, let’s consider the alloys of stainless for knife steel.
Stainless steel is designated as such if it has greater than 13% chromium. However, the ASM Metals Handbook says that it only must be greater than 10%. There are also different numbers thrown around. This difference though, is probably due to the amount of free chromium available. There are many stainless alloys with varying corrosion-resistant properties that make it a good material for knife blades.
420 and 420HC
420 is an extremely soft steel because of the less than.5% carbon content. It will not hold an edge well, but it is very stain resistant, and is often used for less expensive knives. It is also often used to make diving knives. 420 HC is tailored to be more like 440A by including more carbon.
440A, 440B, and 440C
This series of steels increases in carbon content from A -.75%, to B -.9%, to C – 1.2%. 440C steel, if hardened appropriately, is an excellent knife steel. It is very tough, and has good edge holding qualities. It does not hold an edge as good as ATS-34, but is more stain resistant. This complete series is very rust resistant. 440A is most rust resistant, and 440C the least.
AUS-6, AUS-8, and AUS-10
This is a Japanese series of steels that roughly compare with the above 440 Series. The carbon content increasing from AUS-6 -.65%, to AUS-8 -.75%, to AUS-10 – 1.1%. AUS-6 would more closely compare to the cheaper low-end 420. AUS-8 is a middle level steel like GIN-1 or ATS-55. AUS-10 competes with higher end steels, and generally compares well with 440C. It has slightly less chromium than 440C, but all three steels of this series have vanadium added. Vanadium improves the wear resistance and the grain, which gives these steels the ability to be sharpened to a very fine edge. Vanadium also improves wear resistance. These steels are often referred to as 6A, 8A, and 10A.
GIN-1, also referred to as G-2 compares generally to AUS-8, and ATS-55. It has less carbon, and much less molybdenum than ATS-34. It is a little higher in chromium, and typically is used for the less expensive knives.
ATS-34 steel is universally recognized for its edge holding and taking capabilities. It is a Japanese steel that favorably compares to the U.S version, 154 CM, which is not nearly as popular. ATS-34 is definitely stronger than 440 steel so breaking the tip on this steel will be less likely, but it is not as rust resistant. ATS-34, is typically, either hot or cold rolled depending on its thickness, but both are likely annealed (heat treated).
ATS-55 is a level behind ATS-34, because it does not have molybdenum. Without the molybdenum, it does not hold an edge as well, and is not as resistant to rust, and has less wear resistance. It compares favorably with GIN-1, and AUS-8
BG-42 is becoming more popular. It is also more expensive than ATS-34, which may limit its popularity. Because of the addition of vanadium, and twice as much manganese as ATS-34, it will hold a significantly better edge, and will also have better toughness than ATS-34. It is a little harder to work.
S30V, S60V and S90V
This series of steels is packed with a greater amount of alloys because of the particle metallurgy process that is very different from conventional steel manufacturing methods. These are high vanadium knives, and compare favorably with BG-42. They are probably more wear resistant than any other stainless steel. However, they are even more expensive than BG-42, and even more difficult to work. This relegates them mostly to the experienced custom knife maker sphere. S60V is often referred to as CPM T440V, and S90V as CPM T420V.
Whether looking for an easily cared for knife, or a knife that holds a great edge, knowing the options available may give you the best of both worlds.