Naturally Aged Steel ?

Casting yes...minute changes in dimensions due to stress of deep casting techniques, but I can't see anything happening to forged items. I have an old Buck that wouldn't take an edge when it was new 30 years ago...but now, even *I* can get it fairly sharp. Aging or 30 years of practice shapening it? You tell me!

Marketing at it's best...
 
Originally posted by Nasty
Aging or 30 years of practice shapening it? You tell me!
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Probably both.:) As the austenite changes to martensite steel does become easier to sharpen. That's one of the reasons Ed Fowler's knives are said to be so easy to sharpen and yet hold an excellent edge.
There's many excellent metallurgists that know nothing about decent knife steel or the way it reacts no matter how many times they beat on their chest's while exclaiming, "But I am a metallurgist and Know Better!!!!":rolleyes: :D

And the cast iron castings for many machine applications are still aged outside in the weather.
The Swiss Automatic Screw Machine Bases were once aged a minimum of five years!!!! I imagine they still are as the Swiss don't mess with good quaility control.:)
 
Most of this is utter nonsense. Any steel, rail steel, iron nails etc. that is reforged will then lose ANY of the “supposed” mechanical properties gained through aging. Better knives and swords because the rail has been “compacted” with age is just plain myth.
There have been some measurable studies made of release of phosphor but increased hardness due to retained austenite being converted to martensite at room temperature-thus if I read this correctly; a decrease in ductility? I would have to see the stats to believe it.

There are definitve studies for conversion to martensite due to significant temperature change. This will happen at subzero or at heat. In fact subzero quenching’s ability to increase martensite conversation with an average increase of 2 points on the Rockwell c scale with NO commensurate decrease in ductility is measurable, repeatable and provable.


As for edge packing? This is an old smithing term as well as molecular alignment that has been debunked by smiths for decades now. There is no independent gain from steel working-it is a process.
Forge well to reduce grain size and screw up the heat treat…….. Bad product
You could then grind, stress relieve and properly heat treat and have a superior product to forging due to your “process.”

If you forge under too hot a temperature and create a large grain structure, with resultant carbon loss as well, then just cold work your edge and you don’t normalize and then you heat treat………bad product as well.

Successful forging is the result of the proper execution of multiple processes and being intimately aware of your materials.


I have steel that I have had for decades as well as knives and swords. Any measurable differences depends on any given day I happen to convince myself that I like this or that blade better.;)

The only thing I am aware of that gets stiffer, harder, and is less ductile with age……is old men. I have been told that sometimes this can be a good thing.
Cheers
Dan
 
Originally posted by Thomas Linton
Cabela's is selling knives with naturally aged steel: "Blades are cut from the SAME MATERIAL AS old sawmill blades, then ground on a water-cooled wheel TO PRESERVE THE NATURAL TEMPERS GAINED AS THE BLADE AGE." [caps added].
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As you can see the subject was old knives not knives forged from old steel.:D

Originally posted by Dan Harden
Most of this is utter nonsense. Any steel, rail steel, iron nails etc. that is reforged will then lose ANY of the “supposed” mechanical properties gained through aging. Better knives and swords because the rail has been “compacted” with age is just plain myth.

Cheers
Dan
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I agree as any steel that has been age hardened and then reforged loses all that it's gained over the years and becomes in essence, new steel.
However as has been stated there are many old timers who know their old knives keep better edges than they did when they were new and I am one of them, but that's just my opinion and we all know what opinions are like.:rolleyes: :p :D ;)
 
Dan Harden "This will happen at subzero or at heat. In fact subzero quenching’s ability to increase martensite conversation with an average increase of 2 points on the Rockwell c scale with NO commensurate decrease in ductility is measurable, repeatable and provable."

In fact the process never stops, it is just very, very, very slow, it just goes much faster at low temps. I agree that reforging would ruin any aging effect. You could take any blade and cryo it right now. You would need to temper it afterwards which could defeat the point if you changed the hardness, but any new stress in the metal would need to be relieved. Now some metal seem to get alot more benifit from cryo then others, and I would believe that any ageing process would be much less obvious in something that was properly heat treated in the first place. There are about a hundred threads on this over in the shop talk forum. These are my thoughts so please take them as that.
:)
 
In fact the process never stops, it is just very, very, very slow, it just goes much faster at low temps.


**************************************

Hmmmm..........

Again I would like to see any source material for a proven link. If it indeed never stopped then the Broadsword I just had in my hand from the battle of Agincourt must have been dead soft 700 years ago! For now- it is spring-steel hard and bent and resprung over my knee just fine.
Empirical study and proof would be my choice. This myth taken to its conclusion would mean ultimately all steel would become junk.

Start at 58c and in a hundred or hundreds of years you get what? The Rockwell 63 you started with before tempering? That would be like our Nicholson file knife maker friend here....... all over same hardness means?............snap! Sorry bud just a little humor at your expense:D
Anyway any given increase from 59 to 60 over five hundred years? If it were true which I believe it is not.......Big deal! Whoopee! It is so mundane as to be almost meaningless.

Sounds like more collector hoo-ha to me. Men being men. "Gee I have old stuff that cuts better." "Gee I have edge packing with the molecules all lined up." Yup Uh Uh...snore.

Real steel, made and formed really well....is all the magic we need.


I am not trying to be the stick in the mud, and I don't mean to come across as sour. But forging for years and reading and researching tends to give one definitive ideas about things. And the one who wrote that metallurgist don't have all the answers? I agree. But it is the right place to start. Steel is steel.

Cheers
Dan
 
"Sorry bud just a little humor at your expense"


No problems on my end:) I will look to see if I can find those links Here are a few points that i would make though. I would be shocked if a sword made around the time of Agincourt would peg in at 58 Rc when it was made. There are only a handfull of modern steels, such as S5, S7, CMP 3V, maybe 5160, that could be made into a sword hardened to 58Rc and take any kind of abuse, much less full on battle. The carbon level would be the limiting fator on the amount of hardness that you could get no matter what the heat treat or time or whatever. You would have to look at the total carbon in the steel from the start and how much austentite was left to be converted to martensite. I agree with what you say about big deal if it changes a point or two over five hundered years. Perhaps there is a greater change in a shorter period of time in a better steel. More carbon, other alloys etc. Just some things to consider. Edited to add please post any links you have about this topic.
 
Originally posted by Mark Nelson
Edited to add please post any links you have about this topic.
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Well after a while of looking around I found these... The search on Google was titled, "Austenite to Martensite over time."

http://216.239.53.104/search?q=cach...tenite+to+martensite+over+time&hl=en&ie=UTF-8


HEAT TREAT TREATMENT - THE NIKKEN WAY

When steel is cooled down very quickly from a high temperature the composition of the
material changes from Austenite to Martensite, however, at a normal
temperature the Austenite remains in ‘spots’. This composition, called Residual Austenite, reverts back to Martensite gradually over a period of time and causes deformation. In the past, if this occurred, Nikken believe many users experienced difficulties inserting End Mill shanks
into the internal bore of the chuck. To overcome this material
characteristic Nikken have developed a second heat treatment
process which is followed by an innovative ‘Sub-Zero’ treatment:
This ‘Sub-Zero’ process of between -70
°
C to -90
°
C enables Nikken
to remove residual Austenite. The treatment produces a hardness of
HRC65 and incorporates durability and long-term accuracy into every Nikken chuck.

http://www.barrpublishing.com/forging.html

“
Some of the retained austenite will transform into martensite over a period of months after the original quench. This aging process usually results in some change in size over the time period as well. Using a subzero-cooling period can speed up the process.”

http://216.239.53.104/search?q=cach...tenite+to+martensite+over+time&hl=en&ie=UTF-8

“Ok. I'm going to resist why you're using S7 for a spring, then, and just say
that the only possible (though unlikely) issue I can see is the result of
improper quenching and/or tempering. If any high-alloy steel isn't quenched
right it *may* have retained austenite, which *may* convert to martensite
over time (months or years), and cause slight growth as the austenite
converts at room temperature. We're talking about one or two millionths of
an inch per inch of length, except in cases where the heat treatment is
*really* botched.”

http://www.sonic.net/~blade/Info___...Heat_Treating/principle_of_heat_treating.html

If carbon steel is subject to a sever quench or to extremely rapid cooling, a small percentage of the austenite, instead of being transformed into martensite during the quenching operation, may be retained. Over a period of time, however, this remaining austenite tends to be gradually transformed into martensite even though the steel is not subjected to further heating or cooling. Since martensite has a lower density than austenite, such a change, or "aging" as it is called, often results in an appreciable increase in volume or "growth" and the setting up of new internal stress in the steel.

And from other reports I have read from what other knife makers have to say about the matter it's proof enough for me.:)
 
There was also at least one article on the topic in either Popular Science or one of the Physics Journals, that included a bunch of testing and scientific evidence to back up the claims. WIll look around to see if I can find paper I wrote on it, should have the reference so I can find the article.
 
The way I have interpreted the Cabela's ad and some others I have seen on the same theme is that these blades are cold ground from work hardened saw blades.

Edited to copy from Cabela's:
" Handmade Stag Handle Knives
Every knife in this Stag Handle Series is handcrafted by a former blacksmith and horseshoer from whitetail or mule deer antler and hand-polished from butt to tip. Each knife is a work of art, cut, formed and sharpened by hand with a lifetime of knife-making knowledge. Blades are cut from the same kind of metal as old circular sawmill blades, then ground on a water-cooled wheel to preserve the natural tempers gained as the blades aged. Genuine Stag handles, no two are alike. Distinctively beautiful as the animal from which they came. We've added a brass pin through the handle of the two large sizes. Deer head hand-scrimshawed on hunting knife butt cap, and a fish on the fillet knife butt cap. Scabbard is handmade from 10 oz. cowhide. "
 
I ain't no metallurgist, but I do know Yvsa knows his oak tree from his sassafrASS.

Sarge
 
This is interesting. This and deformation is mentioned in a few of those. Just another reason not to do anything rough with really old blades.
 
Originally posted by Thomas Linton
So "natural" tempering is a bad thing?
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Tom I don't thinks so. After all from the material I looked up this change also occurs in low carbon steel as well. If it were a bad thing skyscrapers would be falling from the sky.
There may be a point when it would become prudent not to use a very old blade, but who knows when that point would be reached.
All I know is that my 50+ year old 1095 Marble's and Catteragus hold an edge better than new 1095 steel does and I plan on using them as long as I'm able.:D
Perhaps when late spring or summer comes I may commit sacrilege and test the better/harder of my antique AC bought Nepalese khukuris and see how it holds up.
It would be worth having to replace a handle or even to destroy a blade in the interest of research. Dayum!!!! Did I say, "research?":rolleyes: :D ;)
 
Originally posted by Thomas Linton
I thought Cliff had the corner on breaking the poor critters in the interest of research.:)
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Naw. Cliff just has a few more posts than me.;)
 
Well I went out and did some further research. It's nice having a metalurgist as a father in law. It turns out to be true but there is no definitve answers as to "how much-how long?" A possible answer follows my original comments about whether two points is a maximum (I love learning more about steel after working with it for twenty five years, its humbling.)Ya spend so much time with the new Powder metalurgy exotics and you forget the tried and true-Carbon steel. I simply can't get away from wanting to form Hamon on everything including axe. Uh oh..I digressed again

Anywaym he feels there simply has not been enough research to afford a definitive answer. I offered the following (and it seems to answer the "Skyscrapers would be falling from the sky", and my own question as to how a "700 year old sword is still spring tempered", or how a "700 year sword would be worthlessly hard if they continued to convert to martensite."

_ The subzero quench answer_

The reason the subzero quench works in creating an additional 2 points rockwell c while not havng any contributory effect on reduced ductility is that it naturally converts any retained austenite to martentsite.
1.Now...... if that is true-and it IS a repeatable constant-then perhaps the MAXIMUM allowable transfer of held autenite to martentie results is a MAXIMUM of 2 point rockwell. In other words in simple carbon steels perhaps that is the maximum allowable conversion after initial (set) from hardening at critical heat.

2. Now........if that is the case it makes more relevent sense. There is no doubt that subzero quenching works and 2 points makes a difference if there is no reduced ductility. But an aging factor now has a limiting facotr of the maximum achievable martensite.

Make sense? It certainly is interesting. It isn't that big a deal anyway but interesting nonetheless. There has to be a "set" level, or anything old made from steel would be no good in-time. Which we know is not the case- so what are the limiting factors?


The old marbles knife.
Anecdotal evidence is just that. We don't know what process was used on the original knife, so comparisons are meaningless as to how they are made and tempered now. 1095 (like W1) is a very simple steel. It is better to talk about comparable constants.
If the old were heat treated like the new and the "aging factor" is a limiting constant of 2C- than the old which started at perhaps 58C would now be 60c with no appreciable loss in ductility from the orginal at 58C. While the new would be simply 58C.
Which would make the old; a better knife.

The saw blade grinding comments.
This was touched on years ago in a smithing article. Any grinder jocky or smith will tell you that grinding sets up stress in steel. Enouch so that you can cause deformation in hardening. That said, any grind-to-shape creats stresses in steel. With no additional normalizing/anealling process you can have a flawed blade. Whether grinding below critical temperature or even tempering tempreture you still have a lot of hype with no promise of consistent success. In the end you are relying on the good work of others who made the saws. And you have just added the potential for failure with your own efforts. All well and good since they are little blades.

I wonder if they have each saw or every "X" amount tested prior to and after grinding

Cheers
Dan
 
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