What materials are best suited for making knives: carbon steel & alloy steel

"The standards generally used to measure the quality of cutlery steel are: toughness, corrosion resistance, and hardness. These are related to the material itself and are directly affected by the heat treatment process. Judging the quality of a material based on a single metric is biased. Steel is the formula, and heat treatment is the cooking skill—even Michelin-starred chefs can make instant noodles that are better than street-side steaks, but even the best steel is just scrap metal if the heat treatment is not done properly."

The following is based on a good heat treatment process. Carbon steel is the most basic material for making knives, and everything starts with carbon steel. Structurally, it is an alloy of iron (Fe) and carbon (C). In order to achieve a certain hardness, high carbon steel is often selected as the material, and the more commonly used ones are 1095 and 1084.

1095 is the most widely used carbon steel for knives, offering the best balance. It's extensively used in survival knives and fighting knives, with a wide range of applications. Major manufacturers such as Ontario, ESEE, and Ka-Bar all use it extensively.

Advantages: High hardness; the high carbon content easily achieves a hardness of 58-62 HRC, which is higher than most stainless steels. Good toughness and impact resistance; it is not easily chipped when chopped. Easy to sharpen; it is relatively easy to re-sharpen after becoming dull. Also, it is inexpensive and offers excellent value for money.

Disadvantages: High-carbon steel has poor corrosion resistance (rust prevention), requiring frequent maintenance with frequent use. High-carbon steel is generally used as the blade material, and most blades have an anti-rust coating. After the coating peels off, attention should be paid to rust formation. Carbon steel is the choice of hardcore enthusiasts; if you can accept rust prevention and maintenance, its performance far surpasses that of stainless steel in the same price range!

Alloy steel

Alloy steel is a type of steel made by adding specific alloying elements to carbon steel.

Adjusting the composition ratio achieves targeted performance improvements. Commonly added alloying elements include chromium, molybdenum, vanadium, and nickel. The roles of the core alloying elements are: Chromium (Cr) for rust prevention and wear resistance; Molybdenum (Mo) for increased strength and high-temperature stability; Vanadium (V) for grain refinement and enhanced wear resistance; and Nickel (Ni) for improved toughness (especially in low-temperature environments). These four elements are commonly added.

For example, consider the common domestic alloy steel designation 8Cr13Mov. It consists of 0.8% carbon steel with the addition of 13% chromium (Cr), 0.2% molybdenum (Mo), and 0.1% vanadium (V). The composition is simple and straightforward: Carbon steel (0.8%) + Chromium (Cr 13%) + Molybdenum (Mo) + Vanadium (V) = 8Cr13Mov. Alloy steel is further subdivided into low-alloy steel (alloying elements < 5%), high-alloy steel (alloying elements 5%-20%), and ultra-high-alloy steel (alloying elements > 20%).

Low alloy steel: 5160 (chromium + silicon, spring steel, extremely tough), 52100 (chromium + carbon, modified bearing steel, wear-resistant and sharp). Features: low cost, balanced performance, suitable for heavy-duty knives (such as machetes and axes).

High alloy steel: D2 (12% chromium, "semi-stainless steel", excellent retention), CPM-3V (vanadium + molybdenum, the king of anti-cracking) Features: wear-resistant and impact-resistant, but difficult to process (requires professional heat treatment).

Ultra-high alloy steel: M390 (20% chromium + 4% molybdenum, top-tier rust prevention and retention), ZDP-189 (20% chromium + 3% vanadium, hardness HRC 67 but extremely brittle). Characteristics: Extreme performance, expensive, often found in high-end custom knives. Stainless steel is a type of alloy steel, composed of iron + carbon + high chromium (≥10.5%), forming a passivation film for rust prevention. Stainless steel prioritizes corrosion resistance, with other properties being secondary. Classic examples include: 440c, VG-10, M390, 14C28N, CPM-S60V, etc.

 

In general, high-carbon steel (such as 1095) has high hardness and good toughness, making it suitable for survival knives. Stainless steel (such as 440C) has strong corrosion resistance, making it the first choice for kitchen knives and everyday EDC (Everyday Carry). Powder metallurgy steel (such as M390) is known for its top-notch edge retention, but it is expensive and difficult to sharpen, and is mostly used in high-end custom knives. Tool steel (such as D2, 3V) is designed for extreme wear and impact resistance, making it suitable for heavy-duty survival knives. Regardless of the steel, a good heat treatment process is the key to final performance.