Hint: They're not all the same!
The steel a knife is made from imparts its "personality" on the finished blade. Some sharpen easier, some are tougher, some hold an edge better. All the steels in my shop are chosen for their high potential hardness, ease of sharpening, good toughness, and availability at affordable prices. The heat treatment, profile, bevel grind and final sharpening will matter deeply in how your knife performs in your hand, but the steel must have the right properties for the desired geometry of the blade.
Having said that, some steels excel at certain properties such as toughness, strength, edge retention, stain resistance,or sharpenability. No steel exists that excels in every category.
This list may grow with time, but SLOWLY.
Learn Heat Treating Terms HERE!
A2 is an older air hardening Tool Steel with a good balance of toughness, hardness, and edge retention, capable of 62-63HRc working hardness and very fine edges. With only about 5% chromium, A2 is NOT a stainless steel, and so needs to be cared for to prevent corrosion. A2 benefits greatly from cryogenic treatment, and works well for outdoor knives.
AEB-L was developed for the razor blade industry, and is a stainless steel capable of high working hardness and extremely keen edges. An air hardening steel, it is one of the toughest stainless steels available. Cryogenic treatment adds to strength and hardness.
From Devin Thomas at devinthomas.com:
"Few know what AEB-L steel is, and those that do, only have heard that it is similar to 440B or 440A. The only similarities between AEB-L and 440B or 440A is the amount of carbon. The fact that AEB-L has only 12.8% chromium by weight compared to the 16-17% in 440A and 440B makes the steels quite different. AEB-L is more similar to a stainless 52100 than 440A. A copy of AEB-L called 13C26 is made by Sandvik.
AEB-L naturally forms what is called the K2 carbide, the harder of the two chromium carbides, compared to the K1 carbide, which is formed in steels such as 440C. The K2 carbide is about 79 on the Rockwell C scale, compared to 72 for the K1 carbide. Through proper heat treatment, AEB-L has fine, evenly distributed K2 carbides. AEB-L lies almost perfectly on what is called the "Carbon Saturation Line", which means that all of the carbides formed are precipitated carbides, not primary carbides like are formed in 440C, and there is more carbon and a similar amount chromium in solution as compared to 440C. Primary carbides are very large. So, through a balanced composition, AEB-L has excellent toughness, edge retention, workability, ease of sharpening, and ease of polishing."
Learn more about AEB-L at Knife Steel Nerds:
D2 is an air hardening die steel used to make various cold work stamping dies for metal work. It offers good hardness, great abrasion resistance, very good edge holding, and SOME stain resistance, Best sharpened with diamond stones due to abrasion resistance. Cryo treatment benefits D2 with higher hardness and slightly better edge retention and abrasion resistance. Not high on toughness.
Learn more about D2 Steel at Knife Steel Nerds:
52100 is a high carbon water/oil hardening carbon steel developed for ball bearings and bearing races, capable of high hardness and excellent toughness. 52100 takes an extremely keen edge due to its very fine grain and carbide structure. It is my choice of the low alloy non stainless carbon steels for its fine balance of edge stability, excellent toughness, strength, and ease of sharpening.
Learn more about 52100 steel at Knife Steel Nerds:
26C3 is a high carbon, low allow knife and razor steel very similar to Hitachi Paper White #1, a Japanese blade steel favored by many chefs and line cooks for its extremely fine edge. It is capable of high working hardnesses while maintaining reasonable toughness, and is a great choice for professional cooks and connoisseurs who favor custom carbon steel chef's knives. I've decided to offer this steel for these reasons. Learn more about 26C3 at "Knife Steel Nerds":
What is Cryogenic Treatment?
And What Does It DO??
Simply put, Cryogenic Treatment is a continuation of the "quench", down to -320F. That is, when the knife comes out of the oven at its austenitizing temperature, it is quenched to room temperature according to the standards and protocols for that particular steel. Cryo treatment EXTENDS the quench to -320F. This aids the steel in converting the retained softer phase Austenite to the harder and stronger Martensite. Thus we finish the quench with liquid nitrogen, for an hour to overnight. Afterwards, the tempering cycles are performed as usual. My custom knives deserve the very best heat treat I can give them, and cryogenic treatments improves knives in easily measurable ways.
Dr Larrin Thomas wrote a three part article on his blog "Knife Steel Nerds" about cryogenic temperatures and the effect on knife steels. If you're a knife steel nerd like me, click on the link!