View Full Version : Hot topic, Cold question
06-23-2011, 01:29 PM
I've been reading about 3 pages of back threads on cryo and heat treat. I'm not ready to take a plunge into Liquid Nitrogen but I do wonder. I know I can go down to the grocery and buy a couple blocks of dry ice. I put some K1 kerosene and dry ice into a cooler, lay my knives in and come back a day later (overly simplified). Where do I get LN, how do I use it? I'd sure hate to freeze the wrong thing... :sad:
06-23-2011, 01:50 PM
What a fascinating read.
Per the following website:
Case Studies of Cryogenically Treated Steels
Resistance to abrasive wear was investigated in a parametric study. Five tool steels were tested after conventional heat treatment, after cold treatment at –84 °C (–120 °F), and after being cryogenically treated at –190 °C (–310 °F). Figure 1 and Table 1 show the results of these abrasive wear tests. Cold treatment at –84 °C (–120 °F) improved the wear resistance by 18 to 104%, but the cryogenic treatment results show 104 to 560% improvement.
Corrosion resistance to water-saturated hydrogen sulfide gas was determioned on conventionally processes and cryogenically treated stainless steel and tool steel samples. The results are shown in Table 2. The decrease in corrosion rate ranged from a modest 1.035 to a significant 1.786. The mechanism suggested by these boundaries, which limits the diffusion of hydrogen sulfide into the metal. Type 316, an austenitic stainless steel, is susceptible to intergranular corrosion, and apparently refinement of the grain boundaries did not have as much of an effect on the corrosion rate.
These two scientifically designed studies serve to highlight the effects of cryogenic treatment. Many other case studies with varying results appear in technical journals and engineering publications. The variability of the results listed in these articles does not disprove the effectiveness of the cryogenic treatment. The need for study of any potential application should be apparent, and a careful technical and cost-effectiveness analysis should be made before embarking on such a program.
06-23-2011, 02:47 PM
Different steels require different temps., Thats why I like AEB-L so much, the factory specs. call for only -95 with no soak needed. This easily attained in dry ice. In my opinion dry is is cold enough for D-2 also but thats just my opinion. I too have wondered about the best place to acquire cryo equipment and what the initial cost would be.
06-23-2011, 02:50 PM
Here, the local company that services welders, fire extinguishers, and other pressurized stuff handles LN. As I understand it, the trouble and cost associated with LN is in storing and transporting it. You need a Dewar container that can handle it safely, in fact most places can't/won't sell it to you if you don't have the proper container. Even regular dry ice can go BOOM if you just dump it in a Thermos and seal it up tight - it will gas off as it warms up and create too much pressure.
It's certainly proven that cold treatments and cryo can be beneficial, mostly to steels with a lot of alloying elements that are liable to have more retained austenite if not quenched fully. But I'm pretty leery of claims of 560% improvement in wear-resistance.
06-23-2011, 03:11 PM
AS with all numbers (statistics etc) be wary of specified and implied. Here's the website again if you want to read more. there is a simple (jeff simple) chart at the top of the page that I tried to copy and paste here but wouldn't do it. The chart is really dramatic looking. It took me about a half hour to read (not that I understood it all) but boy, was it fascinating and I really did glean a lot more than I thought I would.
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