A great knife should stay sharp and last a long time. This “Holy Grail” of knife making translates to the search for a blade that is both hard and tough at the same time – two properties which are generally viewed as competing with each other.
One of the main efforts in our journey to create STEELPORT was implementing a heat-treating process that could allow us to create the best possible chef knife in both hardness and toughness. This led us to developing our proprietary 8-step cryogenic heat treatment that pushes our chosen steel (52100) to achieve an extremely hard yet tough 65HRC. This not only blows past the other knives on the market, but even exceeds the steel manufacturers known hardness and stability capabilities.
As a reference, steel hardness is measured on the Rockwell C scale (HRC) and chef knives generally fall into two main “camps” regardless of their place of origin:
- German Style Knives – Known for their toughness since they use a softer steel (54-57HRC). What makes them tough though leads to very poor performance in other aspects – soft steel will simply not stay sharp and the blades must be thick to avoid edge rolling, which in turn leads to undesired wedging.
- Japanese Style Knives – Known for precision and edge retention due to their harder steels (58-62HRC scale) and thinner blades. They are also known for their delicate/brittle edges and are prone to common chipping.
Our search started with the question: How can we combine the best of both styles to reach our no-compromise goal?
The raw product is extremely important, which is why we picked a US made 52100 carbon steel to provide us with the best start. Then we began the very long experimentation process with over 200 samples and 31 conditions to achieve the below objectives:
GOALS:
- Hardness 65HRC -1/+1 – Hardness is a huge factor in steel performance. A hard steel is required for the knife to stay sharp, but this also determines the blade geometry. This is achieved by an experimental process to determine the precise peak temperature needed and consistently maintaining that optimal temperature by using small controlled batches. A simple scientific test for this is to confirm the hardness with a Rockwell testing machine, which we do. But we believe the best tests are performance-based, and to confirm the quality we test the blades by repeatedly cutting through a very abrasive hemp rope. Our blades must get 100+ cuts before dulling which is significantly higher than about30 average cuts in our tests that even typical premium knives in the market get.
- Sharpness & Sharpenability – Hard blades are notoriously difficult to re-sharpen, which is not the case with our knives. Through controlling the grain growth in the heat treating process we have created a knife which is not only shaving-sharp but can also be easily resharpened by the user. All our blades are sharpened one at a time by our head bladesmith and examined before boxing.
- Toughness & Edge Stability – The overall durability of the knife and resistance to chipping. Besides the fact that a forged integral full tang construction is the most durable way to create a knife, we took the added step to do a differential heat treat which creates a hard edge to the blade while leaving the spine and handle durable. This is never seen in production knives since each blade has to be individually processed. Edge stability is the factor which prevents the edge from chipping and is very difficult to find in a blade of this high hardness. This was achieved through a long and proprietary annealing process and adding a cryo step. This is tested by hammering through brass rod and making sure the blade does not sustain any edge damage. This will ensure that the blade will not chip during standard kitchen use of the knife.
We patina the blade as a final step to ensure the blade was properly heat treated, which can be seen by the two different colors to the blade.
We have found that while this process can be very technical, perfecting heat treatment is also an art. It requires patiently experimenting, testing, and treating every new batch of steel as its own entity.
The result is an uncompromising combination of one of the highest hardness levels to keep the edge significantly sharper for longer – and the toughness to keep it the most used tool in your kitchen for a lifetime.
