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Post by sol on Apr 6, 2007 8:06:18 GMT
Cryogenic Freezing or whatnot is a silly way to say 'sub-zero-quench'. A quench is when you very rapidly cool a hunk of steel heated to a specific temperature. The temperature you heat it to and the rate at which you cool it determine how hard the steel is, among other properties based on the specific alloys in the steel. Generally speaking, a more rapid cooling translates into harder steel(more technically means more of the steel grain structure becomes martensitic). Sub-Zero Quenching refers to when you quench in a medium that is 'sub-zero' or 'colder than 0 degrees Celsius'. Liquid Nitrogen is one such medium, though i've only ever heard of knives being sub-zero quenched. Liquid nitrogen is sub zero all right: -320 degrees Fahrenheit. And actually there is nothing silly (it is more accurate) about saying cryogenic freezing as cryogenic means below -238 degrees Fahrenheit (-150 degrees Celsius). Sub zero just means below zero degrees Celsius. Steel could be sub zero quenched and not cryogenically treated.
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Post by Deleted on Apr 7, 2007 9:42:05 GMT
Again, i don't think you can quench in liquid nitrogen, because as i understand it when a blade is quenched it is at a level of cool that counters the degrees of heat with almost instantaneous cooling. The problem is that liquid nitrogen would not be balanced coolness, if you dip ultra hot metal into liquid nitrogen it would snap freeze it and ruin the blade. That is how i understand it anyway. Unless you could heat the metal to a point where it would normally melt and keep it solid, liquid nitrogen doesn't seem feasible.
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Post by sol on Apr 7, 2007 9:53:48 GMT
bloodwraith the link (above) provided by Kriegschwert answers your question of whether it is possible or not... it is. Also differentially hardened katana can reach or exceed 60RC on the ha (cutting edge). Rapidly freezing something with liquid nitrogen does not necessarily cause it to shatter. It would depend on the material being frozen.
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Post by Deleted on Apr 7, 2007 10:38:33 GMT
Yes i read the link but can't find anything about the use of liquid nitrogen and when i think cryogenics i think liquid nitrogen. I thought we were talking about liquid nitrogen here not some other form of sub-zero quenching.
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Post by sol on Apr 7, 2007 10:57:10 GMT
Yes i read the link but can't find anything about the use of liquid nitrogen and when i think cryogenics i think liquid nitrogen. I thought we were talking about liquid nitrogen here not some other form of sub-zero quenching. You're correct to think of liquid nitrogen when thinking cryogenics because that is what is used. We are talking about using liquid nitrogen the article assumes that you know that (the author of the article should have made that clear). Liquid nitrogen (I believe liquid helium can also be used) is the medium used to cryogenically treat steel. Here is a link that better describes the process www.memagazine.org/backissues/membersonly/nov00/features/thebig/thebig.html. Note that the process of cooling then bringing the steel back up to room temperature is done slowly. So technically it might not be considered quenching. Quenching is rapid cooling.
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Post by Deleted on Apr 7, 2007 15:13:37 GMT
Ok, when explained like that it makes more sense because yeah, to me quenching is that rapid cooling and so what i have been saying is accurate but also inaccurate due to a misunderstanding. Thankyou for clearing that up, isn't it nice when two people are right at the same time?
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Post by sol on Apr 7, 2007 15:34:59 GMT
Yeah, basically you can submerge the steel directly into liquid nitrogen, the steel wont shatter. A better method is to bring the steel down to cryogenic temperature and leave it there for a long while then allowed it to warm back up to room temperature slowly. This almost completely transforms all the austenite to martensite without the associated brittleness.
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Post by ShooterMike on Apr 7, 2007 15:52:52 GMT
Just a little more info on the cryogenic treatment of steel...
There seems to be some confusion about the cryogenic process. To be clear, the cryogenic treatment is not used in conjunction with heat-based hardening or tempering. As Adam states, you could never quench hot steel at that low a temperature. The heat in the steel would cause the liquid nitrogen to migrate away from the steel at such a rate as to cause an explosion.
The cryogenic process is done to finished steel. When high carbon steel is hardened through quenching a certain amount of austenite remains, sometimes a lot remains. Austenite is hard but very brittle as it is a "loosely bound" molecular structure. The cryogenic process, which is used later, can convert the austenite into martensite. Martensite is the "good stuff" that you want in a high carbon blade.
"How you know this stuff, shootermike?" is a logical question. My answer is that the cryogenic process has been used for about 15 years to "remove stress" (convert austenite to martensite) from high-grade rifle barrels. And it can make a world of difference in accuracy. It has become fairly common to send an expensive but mediocre-shooting barrel to be "cryo'd" and get a wonderfully accurate barrel back.
Austenite = bad.
Martensite = good.
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Post by sol on Apr 7, 2007 17:24:04 GMT
Cryogenic quenching is done. It is an extension of the normal quenching process whereby the steel is heated to an appropriate temperature the quenched in a conventional manner (in water or oil) then is removed from the quench tank into liquid nitrogen to further facilitate the transformation of austenite into martensite.
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Post by Deleted on Apr 7, 2007 18:22:05 GMT
I think we're all trying to say the same thing and get to the same conclusion, we're all just going about it in different ways.
I like how shootermike sums it up:
Martensite = Good.
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Post by ShooterMike on Apr 7, 2007 20:48:17 GMT
And actually cryogenic quenching is done by some people. It is an extension of the normal quenching process whereby the steel is heated to an appropriate temperature the quenched in a conventional manner (in water or oil) then is removed from the quench tank into liquid nitrogen to further facilitate the transformation of austenite into martensite. Sol, Thanks for clarifying that. I wasn't aware of anyone who produces steel who also had a cryo facility. I would presume (I'm avoiding assuming here ) that you're referring to folks who forge or manufacture steel, not any particular sword maker? But if you are referring to a sword maker, I bet we would all appreciate hearing who it is. Thanks, Mike
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Post by sol on Apr 7, 2007 21:18:16 GMT
Check out bladeforums.com for an example of cryogenic quenching. It's not as sophisticated ( doesn't use expensive equipment to regulate temperature) as the cryogenic treatment you mentioned. It also has questionable results. Here is the link to the thread on that forum www.bladeforums.com/forums/archive/index.php/t-190245.html
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Post by ShooterMike on Apr 7, 2007 21:36:49 GMT
Thanks Sol. That was worth reading. Texas Knife Supply is not too far away from me.
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Post by sol on Apr 7, 2007 22:33:29 GMT
Yep, it's pretty interesting stuff.
I've found that even the experts who work in this field developing the cryogenic treatment of steel often disagree about the methodology and effectiveness of this technology.
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Post by Deleted on Apr 8, 2007 1:20:02 GMT
Well as far as i know to use such a cryogenic process you wouldn't be able to use a hard quench (water) if you were going to use cryo, you would have to use a slow quench (oil) because, and i may be wrong, but i believe it is the process whereby alot of austentite is left behind and the cryo method works by converting austentite to martensite. If you cryo a blade with little austentite it would probably wreck the blade. Cool idea though, but it really would require state of the art equipment which would make the swords very expensive.
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Post by Deleted on Aug 21, 2010 18:28:59 GMT
From what i understand, i think himalayan imports just quenches the edge of their blades with water slowly from a teakettle looking thing. i think this'd be a good way to go as it probably gives great edge hardness but leaves the rest a little softer..i've heard it actually gives really consistent results from the experienced kamis, they almost flawlessly get 58-60 HRC at the edge and like 40's at the rest(combined with the massively thick blades and 5160 steel, that would explain their reputation for being so tough)
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Post by Deleted on Aug 21, 2010 18:29:33 GMT
idk..blacksmithing is mostly still way over my head but id love to learn more and get decent at it someday.
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Post by Deleted on Aug 21, 2010 19:24:54 GMT
I've seen that most of you seem to reckon that a sword hardened to 60Rc will shatter at the slightest impact. I got to disagree, I have my blades hardened to 60Rc on sharp blades and 55-58 on blunt fencing blades. The steel I use is 56Si7, a spring steel. The resulting blade isn't brittle at all but flexes nicely and returns to true. As it is to be expected from such a hard steel, it takes and holds a great edge.
Some demonstration /index.cgi?action=display&board=swordmaking&thread=15119&page=1
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Post by Deleted on Aug 21, 2010 22:35:41 GMT
Tinker has some of his shorter blades (usually 28 or less) hardened to about 58-60RC. My custom had an exact hardness of 58.5RC he told me.
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Post by Deleted on Aug 21, 2010 22:47:21 GMT
Yes, but Tinker draws the middle section of the blades back to 40-45Rc with a torch. I have my blades heat treated to 60Rc without any other application of heat. I'm not saying that that way is any better, I just want to stress that a 60Rc TH blade is absolutely possible, in fact the that's what you want to get and very historically accurate aswell. People should stop believing that you can't go any higher than 52-54Rc.
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