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Types of Steel for Knives - Explained
Knives
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Types of Steel for Knives - Explained

by Adam Roach

Types of Steel for Knives - Explained

Most knife blades use steel in their construction due to its durability, hardness, and edge retention capabilities, especially compared to traditional metals, such as iron and bronze, or more modern ones, such as aluminum or titanium.

However, it is critical to understand that not all steel is the same. Many knife steel materials exist, each featuring different properties affecting the blade's performance and capabilities. In this article, we will explain the types of steel for knives and discuss the benefits and drawbacks of each.

Elemental Composition of Steel

Although steel is essential to many industries, it is not on the periodic table of elements like carbon, iron, or copper, meaning steel is not a naturally-occurring metal. Instead, steel is an alloy manufactured in a steel mill or a steelworks plant.

The essential ingredients found in all steel alloys are iron and carbon, which are mixed together at very high temperatures in a blast furnace. However, most modern steel alloys contain multiple additional elements designed to enhance various aspects of the metal and improve the blade's quality.

The Five Knife Steel Properties

Quality knife steels must balance five properties: hardness, toughness, durability, edge retention, and corrosion resistance.

  • Hardness: A steel alloy's hardness is its resistance to stress and deformation, especially when subjected to significant forces (e.g., applied pressure against a hard object). The harder the steel, the less it deforms under heavy usage. Hardness is measured using the Rockwell C (HRC) scale, and most knife steels range between 55 and 62 HRC.

  • Toughness: Not to be confused with hardness, toughness is the steel alloy's resistance to fracturing under sudden stress (e.g., sudden impacts against hard surfaces). In practical terms, tougher steels are less likely to sustain nicks, cracks, or chips, especially along the edge. Toughness and hardness are challenging to balance because the harder the steel, the less tough they tend to become.

  • Durability: The durability of a steel alloy refers to its ability to resist abrasive wear (loss of material from exposure to harder particles) and adhesive wear (damage from sliding or rubbing against another surface). These types of damage are characteristic of wear and tear from regular use. While durability usually correlates with hardness, using the right combination of alloying elements can also influence a blade's wear resistance.

  • Edge retention: Knife blades are manufactured to reach a specific sharpness level and cutting performance. Although there is no formal way to measure edge retention, some alloys are designed to improve the edge's ability to retain both the shape and sharpness it had when leaving the factory, especially over long periods.

  • Corrosion resistance: The primary ingredient of all steel alloys is iron, an element vulnerable to a specific type of corrosion: rust. The higher the alloy's corrosion resistance, the less likely it will rust or corrode due to humidity or salt. High corrosion resistance typically translates into slightly degraded cutting performance, although it can be mitigated with the right alloying elements.

Steel Alloying Elements

All steels employ iron and a specific quantity of carbon. Depending on the particular steel alloy, your knife blade may contain one or multiple additional elements. Here is a list of the most common steel alloy elements, what properties they contribute to the blade, and how they affect the knife's performance.

  • Carbon (C): Although carbon is found in all steels, not all have the same amount of carbon. A steel alloy with high carbon levels is called high-carbon steel. Adding more carbon increases the steel's hardness and better edge retention, at the risk of making the blade more brittle and vulnerable to corrosion unless mitigated with other elements.

  • Chromium (Cr): Chromium is the primary alloying element needed to manufacture stainless steel. To be considered stainless steel, the alloy must be low in carbon (1.2% or less) and feature at least 10.5% chromium, although most high-quality stainless steels contain 13% to 18%. Chromium primarily contributes corrosion resistance, and, to a lesser degree, hardness. However, high levels of chromium may decrease the blade's toughness and edge retention.

  • Cobalt (Co): Cobalt is one of the world's most commonly utilized alloying elements. Cobalt-based alloys, such as specific types of high-speed steel (e.g., M35, M42), are well-known for their high corrosion and wear resistance. Adding cobalt to steel alloys also tends to increase their hardness.

  • Copper (Cu): Although trace amounts of copper can be found in most carbon steels, intentionally adding specific amounts of pure copper to a steel alloy increases its corrosion resistance and helps protect the metal against the formation of rust.

  • Manganese (Mn): Manganese is another commonly utilized element in steel alloying processes. All steel categories (carbon, stainless, tool) feature alloys with manganese. This element's primary purpose is to increase the alloy's strength and wear resistance, creating more durable knife blades. Adding too much, however, risks making the blade brittle.

  • Molybdenum (Mo): Small quantities of molybdenum help increase a steel alloy's toughness, protecting the edge against chipping.

  • Nickel (Ni): Nickel provides increased toughness, giving it similar properties to molybdenum in alloy steels. Depending on the quantity used and the presence of other elements, nickel can also slightly improve the blade's corrosion resistance.

  • Niobium (Nb): This rare metal is primarily used by steel manufacturers as an alloying element, especially stainless steel. Although small quantities of niobium can improve a steel alloy's toughness and rust resistance, this element's primary property is high wear resistance, providing a knife blade with good edge retention. One of the most well-known steels containing niobium is CPM-S35VN, which is up to 20% tougher than CPM-S30V despite having the same wear resistance.

  • Silicon (Si): Silicon works similarly to manganese; it increases the knife blade's strength. However, its primary purpose is to serve as a deoxidizing (oxygen-removing) agent. Oxygen decreases steel quality and causes pitting and blowholes on the steel's surface, which nickel helps eliminate.

  • Tungsten (W): Small amounts of tungsten can improve a steel alloy's toughness and durability, especially when added to a high-chromium alloy, such as stainless steel.

  • Vanadium (V): The primary purpose of vanadium is to facilitate the formation of vanadium carbides, which increase the blade's toughness. Knife steels containing vanadium are known for their excellent wear resistance and edge retention.

folding knives on a light background close-up

Types of Steel Alloys

Now that we know how steel is made, let's get to the bottom of this: what are the different types of steel for knives?

Steel can contain a near-infinite combination of element types and quantities, resulting in multiple thousands of different steel alloys. Most knife steels fall into three categories: carbon steel, stainless steel, and tool steel. Below are a few examples of each, alongside their pros and cons.

Carbon steels

Carbon steels typically contain high amounts of carbon and relatively low amounts of chromium. Depending on the carbon content, carbon steel alloys are further sub-categorized into three groups: low-carbon steel (0.25% or less), medium-carbon steel (0.25% to 0.60%), and high-carbon steel (over 0.60%). Here are a few examples of common carbon steels:

  • 1095: 1095 is a commonly encountered type of steel and one of the most widespread carbon steel for knife blades. It is high-quality steel with a high carbon content (approx. 0.95% on average). 1095 is employed in constructing numerous U.S. military fighting knives and bayonets, such as the KA-BAR and the M7, due to its high hardness and superior edge retention.

  • 1060: 1060 steel contains less carbon than 1095: approx. 0.6% on average, making it somewhere between medium- and high-carbon steel. Although the lower carbon content results in decreased hardness and edge retention, it improves toughness and ease of sharpening, making it suitable for kitchen knives. The same properties make it ideal for use in bladed tools other than knives, such as axes and swords.

  • Aogami No.1: Aogami steels are proprietary carbon steels primarily manufactured in Japan by Hitachi. Aogami No.1 is a high-carbon steel with a carbon content averaging between 1.2% and 1.4%. Although it is challenging to sharpen, the high chromium and tungsten contents result in exceptional hardness (64-65 HRC), a sharp edge, and superior edge retention, yet less brittle than most steels of similar hardness. It is primarily employed in Japanese kitchen knives.

Stainless steels

Stainless steel knives are characterized by a high chromium content, granting them superior corrosion resistance. Here are a few examples of common stainless steel materials:

  • 440C: 440C is one of the world's most widespread stainless steel, and the type of steel used in Gen II Templar Knives. Numerous knife manufacturers produce blades out of 440C, to the point it is the standard by which other steel alloys are judged. 440C blades contain 1.1% carbon, 17% chromium, and small amounts of molybdenum, manganese, silicon, sulfur, and phosphorus. Knives made using this material feature moderately high hardness (57-58 HRC), excellent corrosion resistance, good edge retention, and good wear resistance. Sharpening a 440C knife is relatively challenging but possible with the right tools.

  • 3Cr13: 3Cr13 steel is a relatively inexpensive martensitic stainless steel type known for its moderate hardness (55 HRC), high toughness, and ease of sharpening. Its chromium content is 14%, and other alloying elements include manganese, silicon, nickel, phosphorus, and sulfur. Although the edge retention of 3Cr13 knives isn't the highest, it is an ideal steel material for beginners learning the basics of knife sharpening and maintenance. Most of our Master USA knives feature 3Cr13 steel.

  • 8Cr13MoV: 8Cr13MoV is another martensitic stainless steel alloy equivalent to the proprietary AUS-8. It contains 14.5% chromium, 1% manganese, 1% silicon, and trace amounts of molybdenum, vanadium, nickel, phosphorus, and sulfur. Although it is considered low-cost stainless steel, 8Cr13MoV knives are known for their high hardness (up to 62 HRC), excellent corrosion resistance, and high wear resistance. Many prominent knife manufacturers, such as Kershaw or Spyderco, use this steel for tactical and self-defense knives.

Tool steels

Tool steel is a category of high-carbon steel alloys designed to manufacture tools. Tool steels are renowned for their exceptional hardness and durability and superior edge retention when used to manufacture knives. Here are a few examples of tool steels commonly utilized to make knives:

  • D2: D2 is a versatile tool steel alloy. It is rich in carbon (1.5%) and vanadium (1.1%) and contains moderate amounts of chromium (12%), low amounts of molybdenum and manganese, and trace amounts of silicon and phosphorus. D2 has both the high carbon content of high-carbon steel and a chromium content equivalent to that of typical stainless steel. It offers high hardness (up to 62 HRC), toughness, durability, corrosion resistance, and edge retention. The only disadvantage of owning a D2 knife is similar to all tool steels: it is extremely challenging to sharpen.

  • CPM-D2: CPM-D2 (also called Powdered D2) is the powder metallurgy variant of the standard D2 tool steel. It features slightly more carbon (1.55%) and slightly less chromium (11.5%) than standard D2. While hardness is similar, CPM-D2 blades are a little tougher and have slightly better wear resistance and edge retention. Additionally, the manufacturing process results in a more consistent and durable blade, making it an excellent choice for knives intended for self-defense, survival, or tactical applications. This high performance steel is reserved for high end knives like the Templar Premium line.

  • S7: S7 steel is a general-purpose shock-resistant tool steel. This steel alloy is commonly found in chisels, shearers, dies, drills, punches, and many other tools designed to withstand extreme impacts. It contains low amounts of carbon (approx. 0.5%) and chromium (3-3.5%), small amounts of manganese, silicon, vanadium, and copper, and trace amounts of sulfur and phosphorus. Knives made of S7 tool steel are exceptionally tough, highly durable, and capable of reaching moderately high hardness levels (up to 58 HRC before heat treatment). While S7 isn't as corrosion-resistant as other tool steel materials, its relative ease of sharpening makes up for it.

Expensive carbon steel japanese knife

Damascus steel

Specific types of steel do not fall into the three traditional categories. The most well-known example is Damascus steel, which does not refer to a single alloy. Instead, the term refers to a mix of multiple layered steel alloys forged together.

Due to the complexity of the manufacturing process, Damascus steel knives are typically produced in small quantities only by specialized artisans and knife-making shops. They are recognizable by the unique wavy patterns on the blade formed during the forging process.

Although the durability and properties of Damascus steel almost entirely depend on the types of steel utilized in its construction, typical high-quality Damascus blades are tough, durable, and highly corrosion-resistant, making them suitable for cooking, camping, and bushcraft.

High-Quality Knives and Tough Steel Blades at Uppercut Tactical

Whether you prefer carbon steel, stainless steel, or tool steel, Uppercut Tactical carries an extensive selection of fixed-blade and folding knives made using the best steel materials for the job. Browse our inventory and find a knife with the best blade steel for everyday carry, self-defense, outdoor applications, and many more.

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