Have you ever wondered why some knives bend easily? Or some blades break when dropped on a hard surface? Have you had a knife that lost sharpness after a few minutes of use? The answers lie in the steel type used to make the blades.
Steel is a carbon and iron alloy enriched with specific elements depending on required product characteristics. For instance, chromium makes steel corrosion-resistant. The elements to add depend on the intended use of the blade.
Since becoming a metallurgist requires going to college, not all of us can tell the difference between clutter and good steel type. This resource aims to enlighten you on steel types, so you can easily pick the right steel blade knife for every job.
Common Elements in Knife Steel Types
Below are the elements that give steel various properties:
- Iron: main steel ingredient.
- Carbon: the main element too but varied in amounts to give steel varying hardness and strength; more carbon results in hard steel.
- Chromium: is an anti-rust additive that gives the steel its stainless property, more chromium results in less rusting steel.
- Cobalt: strengthens the blade.
- Manganese: added to harden the blade, but high quantities make the steel brittle.
- Nickel: for toughening the steel.
- The Molybdenum gives steel temperature resistance properties.
- Tungsten: for wear resistance.
- Vanadium: hardens the steel and adds to wear resistance.
Key Knife Steel Properties
The proportions of the above elements give the steel different properties. There is always a trade-off among these properties though. For example, stainless steel has great corrosion resistance at the expense of being tough.
The biggest trade-off exists in balancing strength, hardness, and toughness. The key properties are:
- Hardness: This is steel’s ability to resist deforming under stress or pressure, measured with the Rockwell C scale. It has a direct correlation to strength,
- Toughness: Chipping and cracking in knives is very difficult to fix—usually, a sudden load or subjection to impact results in chipping. Toughness refers to the ability to resist chipping. There is always a trade-off between hardness and toughness, with an inverse relation; a very hard knife is less tough.
- Wear resistance: steel suffers from two types of wear, abrasive and adhesive. Wear resistance is determined by the steel’s hardness and chemistry. In two steel types of equal hardness, the type with larger carbides resists wearing better but is less tough.
- Corrosion resistance: This is steel’s ability to withstand corrosion from humidity, moisture, and salt. Corrosion resistance has an inverse trade-off with edge performance.
- Edge retention: It refers to how long a blade retains sharpness under constant use. It’s possibly the most important determinant of steel type quality to many knife users. Generally, a steel type with a balance between wear resistance and toughness has good edge retention.
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Types of Best Knife Steel
Common steel types used for making knives fall under three categories:
- Carbon steel: It has the properties of being very tough and durable. Most survival blades contain steel types under this category. Carbon steel is easy to edge and re-sharpen but has low corrosion resistance. A popular carbon knife steel is 1095.
- Tool steel: Steel types under this category make great cutting tools due to their hardness property. Common knife steel types under this category include D2 and high-speed steel M4.
- Stainless steel: These are carbon steel enriched with at least 13% chromium to improve corrosion resistance and other stainless property elements. Stainless steel has low toughness. Popular types under this category are 154CM and CTS steel series.
The naming structure of steel is dependent on the internal structure. Steel undergoes repeated heating and cooling that changes the internal structure to the required. The structures get names depending on the properties they have. Martensite forms after rapid cooling while heat-treating certain steel types, collectively known as Martensite steels. Martensite steel is the most common steel type used in the cutlery industry.
Popular Knife Steel Types
S30V is a Crucible Steel developed specifically for the cutlery industry. It is pricey but makes the best blades. It holds edges well and is resistant to abrasion, thanks to its high carbon and vanadium composition. Major properties of S30V:
- Superior edge holding
- Very ductile
- Good hardness (range Rc 59.5-61)
- Composition: 1.45% Carbon, 4.0% Vanadium, 14.0% Chromium, and 2.0% Molybdenum
Timken Latrobe Steel made BG-42 mainly for the aerospace industry. This martensitic stainless steel is of bearing grade and a high performer. Its strength and hardness make it the ideal steel for blades meant for extreme usage. Major properties:
- Awesome edge holding
- High strength
- Very hard (Rc 61-62)
- Fair corrosion resistance
- Contains: 1.15% Carbon, 0.30% Silicon, 13.50-14.50% Chromium, 4.0% Molybdenum, And 1.20% Vanadium
- Excellent edge-holding ability
- Very hard (Rc 60-61)
- Double-tempering increases toughness
- Fair corrosion resistance
- Less pricey than BG-42 and S30V
- Contains: 1.05% Carbon, 0.35% Silicon, 13.50-14.00% Chromium, 4% Molybdenum
420HC is a standard Type 420 martensitic stainless steel highly enriched with carbon. It’s different from standard Type 420 stainless steel because of its high carbon and chromium content. 420HC has high abrasion resistance and edge-holding. It makes an excellent general-purpose blade after Paul Bos’s heat treatment. Properties:
- Good edge holding
- Re-sharpens easily
- Hardness- Rockwell Rc 58
- Good toughness
- Outstanding corrosion resistance
- Composition: 0.4-0.5 % Carbon, 0.6 Silicon, 12-14% Chromium, And 1.0% Manganese
420J2 is low-carbon stainless steel with suitable hardness, corrosion resistance, and ease to re-sharpen. This general-purpose steel makes good light to medium-use blades. Properties:
- Re-sharpens well
- Hardness- Rockwell Rc 56-58
- Good manufacturability
- Good corrosion resistance
- Composition: 0.36-0.45 % Carbon, 0.6 Silicon, 0.6 Nickel, 12-14% Chromium, And 0.8% Manganese
17-7 PH has great salt-water corrosion resistance due to its Chromium, Nickel, and Aluminium composition. It’s stainless steel made by precipitation hardening. The Chromium/Nickel/Aluminium composition places 17-7 PH properties between Martensitic stainless steels (heat-treatable) and Austenitic (300 series- non-heat-treated) stainless steel. Properties:
- Moderate edge holding
- Excellent toughness
- Rockwell Rc 54-56
- Composition: 0.07% Carbon, 17% Chromium, 7.0% Nickel, And 1.25% Aluminum
M390 is BOHLER MICROCLEAN stainless steel primarily made for molds. It contains high contents of Chromium and Vanadium that improves its wear and corrosion resistance. M390 is hard steel, with excellent gradability and polishability, the best combination for great knives. Properties:
- Extremely high wear resistance
- High corrosion resistance
- Excellent grindability
- High mirror-finish polishability
- High toughness
- Rockwell Rc 58-59
- Minimum dimensional changes
- Contains: 1.9% Carbon, 0.7% Silicon, 0.3% Manganese, 20% Chromium, 1% Molybdenum, 0.6% Tungsten, And 4% Vanadium
VG-10 from Takefu Special Steel Co. Ltd is a popular Japanese stainless steel. It belongs to the ‘Cobalt steels’ type and has strong corrosion resistance. Knives made with VG-10 steel have excellent edge retention and sharpness, making them chefs’ favorites. The vanadium in VG-10 gives it strength and toughness. Properties:
- High edge retention
- Rust resistant
- Re-sharpens easily
- Rockwell Rc 58-62
- Very balanced steel profile
- Contains: 1% Carbon, 15.5% Chromium,1%Molybdenum, 0.2% Vanadium, 1.5%Cobalt, and 0.5% Manganese
Damascus has a long history in the ancient city of Damascus. Today it’s made by pattern welding layers of steel of different steel types. Then steel layers are acidly etched to give it a great color contrast.
Damascus steel is hard to make and is thus regarded as a precious metal. Blades made from this steel are very tough and hence very pricey. Damascus steel blades are beautiful and are custom makes only.
This steel is extremely hard and rust-resistant. Once made, the ceramic steel blades never need re-sharpening. Furthermore, ceramic steel is almost impossible to sharpen. This material is the favorite for scuba knives but results in very brittle knives.
Knife Steel Performance Charts
Here are my rankings for edge retention, corrosion resistance, Rockwell hardness, and toughness:
There exist thousands of knife steel types. The list presented here is not conclusive. Most top-tier steel types with a good balance of the major properties are pricey.
While blades’ obvious use is to cut, the best for you depends on its intended use and location. For instance, for camping, a tough blade suffices well. If you live in humid areas, prioritize a corrosion-resistant knife.
While a common denominator for good knife steel types is the sharpen-ability, other factors that affect steel quality are heat treatment and blade geometry. Still, a steel snob, fret not because everyone was there once.