Anyone have any experiece with this in knife steels?

rhinoknives

Well-Known Member
OK,
I have a self proclaimed knife steel Mavin man that claims that Sabatier carbon steel knife blades have picked up 4-5 RC points because the have been sitting in a box at room temp for 40 years?


He first used the term Steel ageing and then when pressed he called the process precipitation hardening.



I know that there is a way of adding hardening to alumium and some stainless spring steels by increasing the soak time and adding elements Which is a form of Precipition hardening.


Have any of you seem this in knife steels? Carbon Steels to be exzact?
where the steel could picking more RC measurable hardness just from sitting at room temp?

Laurence

www.rhinoknives.com/
 
Seriously??

:s12137:

I gotta say, I kinda hope this is true. :D - I might age mine in oak barrels that were previoulsy used for whisky, for added flavour. :biggrin:
 
Yeah! I think it's BS as far as knife steels are concerned but there is some truth to it from googling the term, precipitation hardening of Stainless Steel.

I am trying to investigate it a bit further and that's why I asked here? Before I tell this guy that I think his head may have some of this age hardening going on.

Anyone ever hear of this concerning Carbon steel, Or any knife steel?

Laurence

www.rhinoknives.com/
 
Well, kinda/sorta, maybe. I can't give you a reference to go to, and may be BS, but I read somewhere that retained austenite will continue to transform to martensite for weeks and into years, but this was a tiny almost insignificant amount. Not enough to add 4 or 5 hardness points. I believe Ed Fowler claims his 52100 blades gain at least 1 point of hardness after 24 hours. I won't dispute that, but I would think 1 point would be hard to measure with any degree of certainty, but maybe not.
 
You guys need to get yourself some books on heat treating and all the rumors will be cleared up. Age hardening is true and is alive and well in the heat treatment world. Too many of you are listening to advice about heat treating that is unproven in a scientific sense. Just because a knifemaker "thinks" a certain treatment of steel is causing this and that to happen to a certain steel, does not mean it is true. Scientific evidence provided from proven testing techniques is the only way to get the right answer.
 
I think a more likely explanation is that there was a difference in the hardness testers used. Also remember that a properly maintained and calibrated Rockwell hardness tester only has a precision of +/- 2HRc . Just that alone could account for a difference of 4 HRc points using the same instrument.

Doug
 
I am not talking about difference in hardness points. If you don't have any books on heat treat procedures, google the subject and read about it. Strain ageing, precipitation hardening, it is all there for you to learn. Learn what happens at the microscopic stage. Here is one I am going to quote to you directly from one of the books I have. "If carbon steel is subjected to a severe quench or to an 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 any additional heating or cooling. Since martensite has a lower density than austenite, such a change or "ageing " as it is called, often results in an appreciable increase in volume or "growth" and the setting up of new internal stresses in the steel." Look this one up: The second step of hardening is to quench the steel at some rate faster than the critical rate. What 3 things are important in the production of a martensitic structure, and what determines the hardness of the martensitic structure.?
 
I have had some experience with old carbon steel saw blades that were extremely hard . Some were 5-6 points harder than the advertised RC
Blades that are left to the elements are subject to additional heating (summer) and cooling (winter) an old saw blade leaning against a garage or some structure facing south can get really hot from solar heat, kind of like your dashboard in summer and then be subjected to cold winter has to have some affect on the steel . If some steel that is hot from solar heat and then subject to a sudden rainfall will harden a little also. Just my opinion ...... Bubba
 
Yes, Tom, I would say that all of us who have posted here are familiar with the fact that retained austinite will convert to untempered martensite and cause embrittlement. That is the reason behind multiple tempering cycles, to convert this retained austinite to martnesite and then temper it. One problem with that with the subject under discussion is that first the steel must be hardened and tempered. Most steel is supplied in an annealed state with does not have retained austinite to convert to anything. We are also very much talking about hardness points. Embrittlement is also accompanied with a rise in hardness, they just tend to to go hand in hand and an increase in one is an indicator of an increase in the other.

Doug
 
You guys need to get yourself some books on heat treating and all the rumors will be cleared up. Age hardening is true and is alive and well in the heat treatment world. Too many of you are listening to advice about heat treating that is unproven in a scientific sense. Just because a knifemaker "thinks" a certain treatment of steel is causing this and that to happen to a certain steel, does not mean it is true. Scientific evidence provided from proven testing techniques is the only way to get the right answer.

Yes, Documented PROOF Is what I'am after!

I have been searching on the net and just purchased a 1964 edition of The Making Shaping and Treating of Steel.
By U.S.S. It's 1200 Pages and I haven't found this topic yet?

If you have found a example of a Carbon steel Picking up 4-5 RC points just by sitting in a box in France or anywhere for about 40-50 years? Please share it with us?

Laurence

www.rhinoknives.com/
 
Our heat treating prices are about to go up if we have to soak 50 years at room temperature for an extra 4 - 5 points. :) Did I mention turnaround time?????
 
I am not the one that said it would go up 4 to 5 hardness points and I have no knowledge of your story of how it was supposed to happen. You will probably find that age hardening has to be done with low temperature heat being applied over a set time. My experience with testing for age growth was a 1.5 point difference overall, but it did get harder from father time and some low temp heat. Embrittlement was present on thin sections and stress points caused cracking which is found by dye testing the blades. Go to Amazon.com and type in heat treatment of steel books. I have spent 34 years making knives and the last 25 years heat treating my own knives and teaching classes on metallurgy and pipewelding for nuclear applications. The books I started with are probably not in print anymore. But you can still find useful info just on the internet
 
Tom.
That was the crazy thing about what this knife Mavin said on Foodieforums.com He was telling someone that some old Sabatier Chef knives that were made after WWII have picked up 4-5 Rc points from sitting in a box in a warehouse and that some were bent from them piling hundreds of knives with no handles in crates. I told him that they were most likely warped from a bad heat treatment process and no one piles hundreds of knives on each other because even in a production of setting of hand forging you still have to move them around and I doubt that there were ever more than 30-50 finished except for handles knives stacked on each other.and asked where he had documetation that these carbon blades were 54 -55Rc when made and that now they are around 59 from Age hardening just from sitting?

I told him that I had read about longer soak times in tempering adding some RC points and some other stuff about Aluminum doing this. Ive looked and can find any on the happening and the man won't respond now because I think he knows he has believed a wife's tale.

I was just interested then if any of you had hear of this Precipitation hardening to this high level in a Carbon steel?
Have you Tom?

Laurence

www.rhinoknives.com/
 
Things are getting deeper and deeper with this. First of all I really doubt that any of those crated blades were individually tested for hardness when made; it was more of a target point for the process. Second, 54-55 HRc is a little on the soft side for kitchen knives so I question that they started out that soft, but I guess that they could have. Again, Rockwell testers are not that precise and this whole thing, if true, could be accounted for by differences between instruments combined with this limit of precision in measurement.

Doug
 
Things are getting deeper and deeper with this. First of all I really doubt that any of those crated blades were individually tested for hardness when made; it was more of a target point for the process. Second, 54-55 HRc is a little on the soft side for kitchen knives so I question that they started out that soft, but I guess that they could have. Again, Rockwell testers are not that precise and this whole thing, if true, could be accounted for by differences between instruments combined with this limit of precision in measurement.

Doug

I agree that a Kentucky windage type of HT hardness testing was done on those knives if anything?

It might of been a get it cherry red and dunk type affair. Which the Japanese were darn good at back in the day! That's quenching by color.

A lot of European cooks knives were about a 55 Rc area for ease of sharpening back before WWII and older. I told this guy that there may be a small increase after HT, But certainly not 4-5 RC points.

I think there was just variation in the hardness when HTed.

He has avoided my post asking for documentation on this.
It's on wwww.foodieforums.com/ in Fred's cutlery corner.. The Thread is" I want a 10" Sabatier"

Thanks everyone and Yes Rob,
HT Costs will sky rocket! if we have to wait all that time!

Cheers!

Laurence

www.rhinoknives.com/
 
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