Non - Cryro Stainless ??

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Plas62

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Which stainless steels for knife making do not require a cryro treatment for optimal performance.
 
Require?

I use 440c and do not cryo with good results each time


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Pretty much every stainless steel requires some type of sub-zero/cryo treatment to get maximum toughness and edge holding. Martensite is the phase that makes the best blade and a freeze/cryo helps convert a larger percentage of Austenite into Martensite. For some steels, freeze/cryo is an absolute must but a few steels will still make decent blades without a freeze/cryo. 440C, ATS-34, 154 CM, & CPM-154 will all make good blades without a freeze/cryo.
If you're doing your own H/T, a dry ice/alcohol bath is very easy to do. I realize that some people don't have access to dry ice but if you do give it a try.
 
The liquid nitrogen sub-zero is optimal but as Darrin mentioned many steels like 440C and those three extended sisters will work fine without it and plenty of knives have been made from them that are still cutting fine. 440C in particular has large carbide clumps that really help hold an edge even without Cryo treatment.
 
I am using CPM154 for slipjoints, any recommendations for a heat treat & temper recipe for the blades and springs.
 
Another vote for Sandvik steels - either 12C27 or even better 14C28N. One of the things I like about Sandvik steels is the short soak time for quenching compared to some of the other steels. Per Sandvik engineers, a short soak at -5ºF helps a tad over no freeze treatment at all, and it's easy to do in a home freezer, so why not.

Ken H>
 
Thanks for the response. Next time I buy steel I think I will go with the Sandvik 14c28n.
 
Looking closely at the Sandvik information, the 14c28N steel shows about 2 pts gained in RC by -5 cryo and another 2pts gained by deep cryo (these gains are interpolated by the gains in hardness at his/their first reported tempering effect).
So, I think that their steel does likely benefit a good deal from cryo. However, I am not at all saying that it wouldn't be one of the best choices for a stainless knife without cryo.

I made a chef's knife of 440c recently, and I was shocked by how well it sliced compared to how well it push cut. I am used to 1075 and W2. So, the difference from what I expected was pretty significant. I now think I understand that this was due to the big chromium carbides leaving a, "toothy," edge as they ripped out. Honestly, it was a refreshing find.

Thanks for the information in this thread, guys. It has been very good.

Kevin
 
The reason why extended quenches are used is because when steels get a very high alloy dissolved into the austenite it lowers the Mf point and thus at the end of a traditional quench, which is at most room temperature, there is still a lot of retained austenite which is soft/weak. A cryogenic treatment also does something different as it causes the precipitation of a different type of carbide (eta) and cryogenics often shows significant changes in wear resistance - however this carbide gain is coupled with the hardness gain (and removal of austenite) so it isn't always clear what is having the largest effect.

If you want to harden stainless steels to martensite and not require extended quenches :

-use a low alloy stainless like 3Cr13

-put up with large amounts of retained austenite for increased gross toughness and ease of grinding

-use hot tempering and secondary hardening to produce very hard and high wear resistance stainless (though compromised in toughness, edge stability and corrosion resistance)

The last one used to be the norm in the industry for a long time, even Bos used to to it that way.
 
John D. Verhoeven's book Metallurgy for Bladesmiths has a procedure for minimizing retained austenite in simple stainless steels, like AEB-L, 13C26, 12C27, and similar steels. He lowers the austenizing temperature to ~1900 degrees F, oil quenches, and tempers at 380 degree F range, and maintains a hardness above 60 HRc, specifically with AEB-L. The amount of retained austenite when quenched from 1900 F to room temperature was minimal, 6% or less. Oil quenching is recommended.
 
He lowers the austenizing temperature to ~1900 degrees F, oil quenches, and tempers at 380 degree F range, and maintains a hardness above 60 HRc, specifically with AEB-L. The amount of retained austenite when quenched from 1900 F to room temperature was minimal, 6% or less. Oil quenching is recommended.

The problem is at that low a temperature the chromium put in solution will be lowered significantly, hence why the retained austenite is low. If you check isothermals, that temperature has about 9-10% Cr in solution which is going to compromise the corrosion resistance significantly. If you are going to do that it would be more sensible to drop back to 12C27M or further unless the hardness is more important than the corrosion resistance.
 
A quick look and some dirty interpretation of the charts looks to be around 11%, though still below the threshold of 12%. Depending on the use and intent of the knife, hardness could well be more important than corrosion resistance. However, someone else asked a similar question a while ago. I'll have to go back and amend my posts there now, as that change could make a difference they don't want.
 
our local welding gas supplier sells dry ice for $2/lb.
A 2 pound block is all you need for a -100F cryo.
I used a 2lb block a few weeks ago and gained 1.5hrc so that appeared to be enough to make a difference.
 
A dry ice/acetone bath will get cold enough to take care of the RA..I measured our last batch at -106°..I isn't cold enough for "true" cryo but you will generally get the same RC gains from the RA reduction as you do with LN from what Ive seen. Just not the cryo's eta carbide" formation..
 
A dry ice/acetone bath will get cold enough to take care of the RA..I measured our last batch at -106°..I isn't cold enough for "true" cryo but you will generally get the same RC gains from the RA reduction as you do with LN from what Ive seen. Just not the cryo's eta carbide" formation..

From what I understand, AEB-L has just enough Carbon to get hard but not formulate any carbides. It was formulated specifically for that reason, which is why it takes such a keen edge and is so easy to sharpen. Maybe someone more astute than me can correct me if I'm wrong but taking this into consideration, LN is probably overkill on AEB-L.
 
My understanding on AEBL-L is that you take it to the low temp but a soak is not necessary.
Others can chip in what they know.
 
In order to get the properties it was designed for, hardness/corrosion resistance it needs to be soaked. It has, depending on the soak temperature, <5% chromium carbides by volume and they are very small, on the order of ~micron. It can reach a hardness of 64/65 HRC after tempering and has high corrosion resistance, dishwasher safe. But again, the soaking is critical as is the quenching. If the soak is too cool/short, or the quench is slow, there will be a reduced amount of carbon and chromium in solution which will lower the hardness and corrosion resistance. A few pictures, first AEB-L :



ATS-34 :



S110V :



Landes on 13C26 (same steel, different name) :

  • Furnace: Vacuum, protective gas, or salt bath
  • Preheat 1: 450-600°C equalize 3-5 min
  • Preheat 2: 850-950°C equalize 3-5 min
  • Austenize: 1065°C eqalize 3-5min, hold 5min
  • Quench: oil preheat to 60°-80°C; N2 4bar
  • Cryo 1: immediately after quench min. -70°C or lower, hold 1h
  • Temper1: 150°C for 1h, then quench in Water
  • Cryo 2: immediately after quench min. -70°C or lower, hold 1h
  • Temper 2: 150°-180°C for 1h, then quench in Water
 
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