ApexUltra is a steel, specially developed for handmade knives. With its high purity and well-balanced alloy composition, it has the highest toughness of all knife steels, tested so far in the 66+ HRC range, along with excellent edge retention.
For which knives is ApexUltra best suited?
With its combination of high hardness and toughness, ApexUltra works very well with knives with thin and sharp edges. Kitchen knives, razors and carving knives are examples of good applications.
How to forge ApexUltra?
The forging and welding behaviour, can be described as similar to 52100, therefore recommended for beginners, but is perfect for those looking for the next level of performance in carbon steel knives.
How is ApexUltra better than other steels?
Hardness and toughness are typically a balance where you sacrifice one to gain the other. There are only a few factors that benefit both: Purity and homogeneity as well as a fine grain and fine carbides are what we look for in the perfect steel for knife applications.
Most steels contain some inclusions that do not benefit the steel but represent small defects, where cracks and corrosion can start their attack on the steel. If there are fewer places to easily initiate a crack, the overall toughness of the material increases. Why aren't all steels super pure? It requires extra steps in manufacturing that cost money, and the cheapest grade is sufficient for many general applications. Not everyone spends hours working on a few hundred grams of steel to make a tool designed to terminate in an infinitely fine wire.
As with purity, homogeneity is important in making the entire material consistent: this ensures that there are no soft or brittle spots in the material, so that the overall blade is durable.
A fine grain
A fine grain increases hardness and at the same time toughness. A proper heat treatment protocol will ensure that you get the most out of the steel, but the design of the steel itself can also help: the presence of small carbides at the forging and heat treatment temperatures ensures that there is no drastic growth of the grain during processing, so that a fine grain structure is easier to obtain.
The volume fraction and hardness of the carbides control edge retention in CATRA and rope cut resistance tests. The largest carbide size is related to a material's toughness, so fine, hard carbides usually achieve the greatest edge retention for a given toughness. Existing low alloy and high hardness steels contain larger primary carbides and/or martensite for plates - both of which drastically reduce toughness. ApexUltra is designed to avoid these problems and the successful structure can be seen in the micrographs and hardness/toughness ratio diagrams.