The core steel (Hagane)
I use few different steel. This allow me a better understanding on it's qualities and to dial heat treat them to the best of my skills.
Hitachi Shirogami #1 is one of the purest steels available, refined from superior quality steel, the Shirogami 1 is extremely fine grained and once forged and heat treated, displays phenomenal sharpening characteristics.
Takefu V-Toku #2 is a high carbon (1.05%), tungsten (1.25%) steel that form hard and compact carbide. Made in Japan by the Takefu special steel company. It has improved toughness which reduces chipping and extends edge retention
26C3 Uddeholm is a very high carbon (1.26%) steel with closely controlled alloy content and low impurities. Originally developed for making scalpels and razor blades, it has very fine grain structure and the highest potential for sharpness.
135Cr3 Bohler is a low alloyed, high carbon (1.35%) steel commonly used for the manufacture of rasps, files and, more broadly, all sharp tools requiring strength, reliability and hardness.
C130 / C125U is a the low alloyed steel with high carbon content. This grade is no longer used in industry and is becoming rare on the European market. Its low content of alloying elements requires water quenching.
115CrV3 Silver steel is a high carbon (1.15%), low alloyed steel. It has been widely used to make, engravers, screwdrivers. Sheffield silver steel is used in France for straight razors and in Finland for Puukko knives.
Core steel 135cr3
Core steel 26C3