Steel is a material that’s used for many purposes, including knives. There are a few main types of steel, and they differ depending on their chemical composition.
The main qualities that knife steels should have are hardness, toughness, and corrosion resistance. However, these elements are often sacrificed for other properties when developing a particular steel.
Hardness
Hardness is important for a knife because it determines how long it will stay sharp. Blades with higher hardness will also be less likely to chip or break, which is why they’re often used for precision cutting and slicing.
The hardness of a steel is measured using the Rockwell Hardness Scale. This scale ranges from 100 to 500, with lower numbers indicating lower hardness.
If a steel is too hard it will easily chip and break, making it unsuitable for use. On the other hand, if a steel is too soft it won’t hold an edge well and will need to be sharpened more frequently.
The hardness of a steel is controlled by its carbide content, which is how much carbon it contains. A steel with high carbide will have more wear resistance and edge retention than one with low or no carbon.
Toughness
A knife steel is designed to provide a balance of qualities, such as toughness and wear resistance, that can optimize its performance in a variety of situations. This is done by heat treating the steel.
Each step of the heat treatment process alters the alloy distribution and transforms the soft matrix into a hard matrix capable of withstanding the pressure, abrasion, and impact inherent in knives.
This is important because most knife failures are the result of conditions that cause wear, such as applied loads and abrasion environments. Toughness data can predict which steels may be more or less prone to chipping or breakage than others, but it is not sufficient for predicting the performance life of a knife.
Corrosion Resistance
Corrosion resistance is another one of the properties that makes a knife steel unique. It is how well it will resist corrosion from water, damp environments, and salt.
Corrosion can dull your edge, cause pitting, and damage the structural integrity of the blade. Stainless steels are typically more resistant to corrosion but that does not mean they will never rust.
Some high-end knives are made with a special stainless steel that is specially formulated for corrosion resistance, such as San-mai or CTS-BD1. American stainless steels produced by Carpenter Technology using vacuum-melt technology provide stainless properties with high hardness and excellent wear resistance.
Edge Retention
Edge retention is the ability of a blade to maintain a sharp edge over time. It can be affected by several factors including wear, micro-chipping, deformation and corrosion.
Hardness is the key factor here because higher hardness leads to better edge retention. It is possible to get excellent edge retention with a steel at low hardness but it will be much harder to sharpen and the edge may not be as fine as you would prefer.
Toughness is a more complex issue because toughness is related to the amount of carbides (hard particles formed between carbon and another element like Vanadium or Tungsten) in the steel. The more hard carbides a steel has the more wear resistance it will have but the less toughness it will have.
There are many different types of knife steels, some with a lot of carbides and others with little or no. They all have their own set of characteristics that make them work best for specific applications.