Not widely known Japanese alloy, ATS-55 is similar to ATS-34, but with the Molybdenum content reduced and new elements added.
It looks like the intent was to get ATS-34 edge-holding with increased toughness. Since Molybdenum is an expensive element useful for high-speed steels, and knife blades do not need to be high speed, using much less Moly hopefully decreases the price of the steel and at the same time retaining ATS-34's performance.
It is used by Spyderco.
ATS-34, a Hitachi product, is concidered to be the ultimate, all around knife steel. It is the Japanese version of 154 CM and, comparing the alloy content, these two steels are interchangeable.
154 CM was developed by Crucible Metals as a high temperature alloy for use in fan-jet engines. 700 degrees F would not soften it and has enough Chromium to make it stainless in normal use.
Normally hardened to around 60 Rc, it holds an edge very well and is tough enough even at that high hardness. Not quite as rust resistant as the 400 series stainles.
Used by many custom makers, Spyderco (in their high-end knives) and Benchmade
Color coding
Color code on the end of the ATS-34 bars is Red.
Heat treating:(as done by Paul Bos)
AST-34 is a secondary hardening steel. That means it gets harder with the freezing and tempering, usually gaining 2 -3 Rc points.
Heat to 1975 degrees F and soak for 40 minutes. Quench in Argon or rapid quench in air, straighten as necessary before freezing to 120 degrees F, than freeze to below 220 degrees F for 6 - 8 hours to transform retained austerities.
Double temper at 950 degrees F, 2 hours for each temper. This gives a final Rc of 59 - 60.
Compared to: 440-C when tempered from 950 degrees F gets only 54 Rc.
Available hot rolled or precision ground and in the sizes used by most knife makers.
