Hardened steel is the heart of any blade. The search for higher-performance steels has led to a number of metallurgical advancements in recent decades, with what some refer to as “super steels”.
Essentially steel is a combination of iron and carbon that is often enriched with other elements (alloys) to improve certain characteristics depending on the desired application. It is these additions that give different types of steel their special properties.
You’ll often hear people asking, what’s the best steel? Or is this steel good for knives? Well, the answer depends so much on what the knife is being used for, and how the steel is heat-treated. For a knife lover, it’s worth spending a little time understanding steel properties to appreciate what the “best steel” might be for his/her application.
Common Knife Steel Types
The most common blade steel types generally fall into the following categories:
Carbon Steel – These steels are most often forged and are generally made for rough use where toughness and durability are important. They take a sharp edge and are relatively easy to re-sharpen in the field. The trade-off is that they are more prone to corrosion. The most popular carbon knife steels are various tools steels, 5160, 1070 and 52100.
Stainless Steel – Basically carbon steel with added chromium (in recent years chromium has been replaced with nitrogen) to resist corrosion and other harsh elements. Note that to qualify as a true stainless steel there must be at least 13% chromium content as a rule of thumb. Some popular steels in this group include M390, Elmax, N690, AEBL, 19C27 and 440C.
Damascus Steel – Also known as pattern-welded steel and is instantly recognizable by the swirling and eye catching patterns caused by the folding two different steel repeatedly, until there are as many as 100 or more layers in the piece. Depending on the steels/metals used, damascus steel can be stainless or not. The pattern in damascus steel is only visually revealed once the steel is cleaned, prepared and etched in acid. The two types of steel react differently in the acid oxidation process. One oxidized steel is lighter and the other is darker.
Regardless of which type of steel used in knife blades, each will exhibit varying degrees of these five key properties. None will be rated as high or low across all five properties, in reality it’s a trade off between what characteristics you want from the blade / knife:
Hardness is the ability to resist deforming when subject to stress and applied forces. Hardness in knife steels is measured using the Rockwell C scale (aka “HRC”). Scale C is specifically used for rating the steel used in knives. The hardness of a knife is very important as far as its performance and durability. For instance, a harder steel with a RC of 58-62 will hold an edge better than a softer steel. However, that same harder steel is less durable and more prone to chipping or even breaking.
Toughness is the ability to resist damage like cracks or chips when subject to impact and also the ability to flex without breaking. Toughness and Hardness share an inverse relationship, ie: the harder the steel the less tough it’s likely to be (and vice versa).
Wear resistance is the steel’s ability to withstand damage from both abrasive and adhesive wear. Wear resistance is also heavily influenced by the specific chemistry of the steel. In general, the steel with larger carbides (think microscopic, hard, wear resistant particles) will typically resist wear better.
Corrosion resistance is the ability to resist corrosion such as rust (oxidation) caused by external elements like humidity, moisture, acids and salt. This can make for a low maintenance, practical blade.
Edge Retention represents how long the blade will retain its sharpness when subject to periods of use. Edge holding is a function of wear resistance, strength, and toughness combined to produce an edge that resists deformation under use. Cutting thick cardboard or hessian rope are both popular tests to measure edge retention.
What is the best steel really?
In the knife industry, dozens of different types of steel are used and varying price points. By understanding the above properties, you will have the fundamental understanding of steels and how the choice of steel can affect the performance of a knife. Some blades can be made to be exceptionally hard but will chip or crack if you drop them onto a hard surface. Conversely a blade can be extremely tough and able to bend but will struggle to hold its edge.
The performance of a knife is not solely based on the steel used in the blade of course. Heat treatment, blade geometry, handle ergonomics and materials all effect how a knife performs for a particular job. How the knife maker combines these elements, ultimately demonstrates his or her artistry.
Parting thought: Just because a blade is made from the premium or high-end steel does not automatically mean it’s “better” than the lesser steels. In reality, all modern steels will perform well enough for most users so consider spending more time on other aspects of the knife, such as the blade shape, balance, overall fit and finish and other cosmetic features.