Check my HT Recipe

Josh Dabney

Moderator
Here's my situation. I am a newb, but one who's serious about making the best knife I can make. I've got some 1095 CRA on the way from Admiral. I've got my evenheat up and running so accurate temps aren't a problem.

I've done all the forum research I can do. I've read, re-read, and re-re-read Kevin Cashens stickies at BF concerning Quenching and Hypereutectoid steels and have made up my "proposed" HT Recipe based on my conclusions from the research I've done.

I'll include my thoughts on some aspects to explain the reasoning for my choices. Every word and detail is welcome to scrutiny and correction if in error.

I am aware that HT is a largly personal thing and success is generally a measurement relative to the user of the end product. Realizing this I understand that having a recipe is a begining not an end to the creation of the best blade I can make but we've all got to start somewhere right.

Begining with 1095 CRA barstock from Admiral steel

1. Cut, profile, rough grind
2. Normalize ( to refine grain and relieve stress)
-Heat at 1475* and air cool to magnetic
-Heat to 1375* and air cool to magnetic
-Heat to 1275* and air cool to magnetic (Are these temps good ?)
3. Harden Place blade in oven at 1275* and bring to 1475* soak 10 min
-Soak time to evenly distribute carbon, not just get it into solution
4. Quench (and agitate) for 10 seconds, remove, straighten, air cool to ambient. Got Canola oil now but hope to get McMaster Carr 11 second before using the 1095.
5. Temper kitchen oven 350* 1 hour.
6. Dry Ice cryo over night
- I am aware that cryo probably won't add any RC hardness or wear resistance to basic carbon steel but should aid in getting a complete, or more complete martensitic transformation and eliminate retained austintite. (It can't hurt right?)
7. Temper in Evenheat 400* 2 hours
8. finish grind, sharpen, test, finish knife or temper again +25* if edge chips
9. Smile, laugh, and live happily ever after.

This is where I'm at but do still have one question. Assuming I wanted a differential HT should I go with a softback draw or edge quench to achieve that ? Also at which point in the process to softback draw, before first temper,after first temper,or after cryo?

Again please feel free to tell me the errors of my thinking as this stuff is just a tad difficult to digest for a newb.

Thanks in advance to all who reply and my appologies for resurrecting this dead horse

-Josh
 
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Sean Cochran

Well-Known Member
Josh
I use alot of 1095, and my HT is pretty close to what you have except for the first temper and cryo. Im not sure it is going to be any benefit. With the recipe you have I dont think you will have a problem with RA.
As for the differential hardening, I have tried edge quench and drawing back, I prefer the former just because it is very easy to get heat further up the blade than you want, the heat will keep climbing even after you remove the heat source and it is painful to watch that color migrate from the spine to the edge of the blade (ask me how I know:eek:).

Just my .02 but it sounds like you are on the right track.
Here is a pic of an edge quench that I did. I bead blasted it and love how it looks.

 

SBuzek

Well-Known Member
Josh
Since it's CRA and you are not gonna forge it you can skip the normalizing steps.Also the cryo won't hurt , but why spend the money on dry ice for no gain.
Stan
 

Josh Dabney

Moderator
Stan, You are correct to my understanding about not "NEEDING" to normalize CRA steel thats been stock removed. The only unknown variable is the state of the steel from the mill so I figure if I've got my oven heated up why not normalize and be SURE I'll end up with a good grain structure even if it shouldn't be needed.

If I understand refining grain correctly this can only be beneficial to the end product.

My thoughts on cryo. Full martensite is the goal. I've seen it questioned many times concerning everything but Parks #50, Is this Oil, Goop, Comercial quenchant etc. fast enough for 1095. If I was planning on using the Parks I probably wouldn't consider cryo benificial. Here is where I may be off base... Lets say for example I'm quenching in canola oil. It will harden 1095 and make a useable knife, but am I getting full potential of the steel ? If not.... WHY. I'm assuming that you will get incomplete martinsitic transformation meaning retained austentite or one of the other undesired possibilities.

So I'm concluding that the cryo is just insurance that I'll get full martinsite.

Again I could have fouled understanding or logic along the way somewhere here. The added benefit of using a lower tempering temp in the kitchen oven followed by cryo is that will give the Evenheat time to cool with the door closed saving life on the elements and still get the benefit of accurate temp control for the final temper.

Sean, My reasoning for the lower 1st temper is just that I won't have to worry about the kitchen oven overshooting my desired temp an robbing the blade of some hardness. The second temper should still get me in the right place.

Thanks for responding fellas -Josh
 

jkf96a

Well-Known Member
I'm open to being corrected, but to my understanding the problems with not achieving full hardness in 1095 will be related to pearlite in the blade from having the quench medium too slow. Retained Austentite is more in the realm of high alloy steels.
 

Doug Lester

Well-Known Member
You may need to look up the austinizing temperature for 1095. I'm not certain that all the temperatures that you listed will austinize the steel. I don't have an IT diagram for 1095 in my reference material but I did find one for 1080 and it looks like the austinite start temperature for it is around 1325 degrees F. Always check with a magnet. Remember you cannot normalize steel without austinizing it first as it involves reforming the crystals at phase change. I have spheroidized steel at 1275 degrees but that takes a soak of one hour.

Another thing, trying to straighten the blade right out of the quenchant is asking for a broken blade. Remember that the steel is full of untempered martinsite and retained austinite as it comes out of the quenchant and is very brittle. I just had the experience of snapping two blades after tempering at too low a temperature for three two hour cycles. Even though the temperature was too low some of the martinsite had been tempered and you're thinking about doing it with completely untempered martinsite.

Cryo treatment will not increase martinsite, as I understand it it only further refines the grain. Martinsite if formed when austinetic steel is rapidly cooled below the martinsite start temperature, for 1080 that is about 425 degrees. To convert a steel to 100% martinsite you have to rapidly lower the temperature of the steel to just above the martinsite start temperature for about 5 seconds to allow the core temperature to equalize with the outter temperature and it is then air quenched. This is usually done in a low temperature molten salt bath but can be done in hot oil. Be advised that if you use oil that is not designed for this purpose you will be working with it near it flash point and it will probably burst into flame when you put the bright hot steel into it.

One other thing is that simple steel like 1095 will not convert to 100% martinsite unless you have large grain size because it is a shallow hardening steel. Depth of hardening decreases with grain size. If you have good grain size the steel will form martinsite in the section of the blade that is not more than twice the depth of hardening. In the sections of the blade that are thicker than that pearletic steel will form. There is no way that I know of to measure or estimate the depth of hardening during this process.

My infromation comes from John Verhoeven's book "Steel Metallurgy for the Non-metalurgist, a book that I highly recommed that any knife maker get whether they forge or grind. Mr. Verhoeven has a doctorate in metalurgy.

Doug Lester
 
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SBuzek

Well-Known Member
Josh
If your quench is not quick enough you form pearlite,not marstinite so cryo will not convert pearlite.Only a faster quench will do that.
On the normalizing like you said can't hurt since your doing it in a kiln and temp. will be controled.
Stan
 

burchtree

Well-Known Member
Always normalize. You never know what has happened with the steel before you got it, and you might as well start with a clean slate. :)
 

Josh Dabney

Moderator
Thanks a ton for the info guys,

I wasn't sure but I'll agree that cryo is indeed a waste of time and effort with 1095 so I'll scratch that completely.

Doug, google search info... 1095 austinising temp = 1436*

This is purely info read but as I understand it you will have a couple minutes right out of the quench to straighten the blade while it is convering to martensite. If you wait say 10 minutes then try straightening that would be a major cracked blade hazard. I would be straightening the blade after the first normalizing heat and checking thereafter for further warping after each normalizing heat. I guess I should have put that info In my recipe.

Thanks again, Josh
 

Doug Lester

Well-Known Member
Conversion of austinite to martinsite is a very quick process. If the cooling process is not done very quickly you will end up with pearletic steel. Plus you have to hold the steel in the quenchant long enough to reduce the temperature far enough to keep the retained heat from tempering the steel. If you try to straighten the steel right out of the quenchant you will break blades. Untempered martinsetic steel is under such stress that it has been known to break just sitting on a counter. It is important to go immediately from quenchant to the tempering oven. The best time to straighten is after narmalization. Some have done it immediately after removing the blade from the tempering oven.

I know that I'm speaking against myself but you have to use a little caution with some of the information that you find on the web. There are no editors to check out the information posted. I remember when I was researching knifemaking before I got started. I ran into a post where the author stated that the only people who do hollow grinds are those who don't know how to use a grinder. Unfortunantly I didn't know, and apparently he didn't either, that there are examples of hollow ground blades almost two millinia old and that the grind does have a purpose. I also ran into a description of the difference between cast iron and wrought iron that was just a little too quick and dirty. There are master smiths on this and other knife maker's boards who will be more than happy the help out the newbie and a good library is indispensable.

Doug Lester
 

Delbert Ealy

Forum Owner-Moderator - Founder
Doug,
I believe the process Josh is trying to decribe is marquenching or martempering. Once you get below the pearlite nose you can interrupt the quenching process and let the blade cool more slowly. This allows time to straighten any warping that occured in the quench. I do a similar process with O-1 and L-6 and these steels respond very well. I am not sure about 1095. I am sure that verhooven covers it, probably in conjuction with salt bath heat treatment.
 

Rusty McDonald

KNIFE MAKER
I agree that it is very quick but you can still straighten a blade out of the quench. I have done it many times and have seen master smiths do it as well and it has never hurt the proformance of the blade one bit. After quench if your grind isn't perfect you will have a slight bow to one side or the other some time you can see it some times you cant, it's the nature of the beast because of the steel contracting more on one side than the other.

This is one of those questions where you ask 10 smiths and you get 100 answers from them. There are many ways to do it. some are right some are better than others some are scientific and have books to back up the answers and some just work does that make it wrong, IMO no it doesn't. Find what works for you consistently and use it. After all it is consistency that your looking for not perfection. But if you can perfect consistency then you have something.
 

Josh Dabney

Moderator
Thanks again everyone for helping me get basic starting understanding of all of this info.

Delbert is correct. Thats exactly what I had in mind. Get the blade temp under the martinsite start temp then cool in still air . I didn't know the correct terminology to describe the process so thanks alot Delbert for cluing me in on it.

Doug- I understand what you mean about taking it with a grain of salt. As Rusty mentioned I recall reading about straightening out of the quench from very reputable sources but do not remember exactly when and where I read the info so I won't mention names as I couldn't verify the info.

As Delbert mentioned there is still the caveat of the type of steel and perhaps this could cause a problem with 1095 even though it'll work fine on another steel type.


As we know the speed of the quench is the crucial element to success with 1095 so let me ask if you guys opinion as to whether the McMaster 11 second is fast enough for 1095. I've read others who say 1095 is fine with this oil but I thought I'd ask your opinions .

Thanks again for participating in this discussion, Josh
 

Doug Lester

Well-Known Member
Now that we are on the same page, what you are saying does make sense. Actually I described the process of martempering in one of my posts. You still need to austinize the steel before you can normalize and 1095 is still shallow hardening. Josh, you are getting pretty bold in your heat treatment for a beginner. No critisom, just an observation. I really do recommend that you get Verhoven's book. It was a a big help to me in understanding what goes on with steel. Amazon carries it. It's sort of Cliff Notes for metalurgy and it's organized to aid study.

Doug Lester
 
M

Mook

Guest
At the risk of sounding like a heretical idiot, it sounds like you're working WAY too hard if this is your first knife.

Bear in mind that I'm a noob too, a hobbyist, and a prime example of adult ADD. But...if this is your first knife, I'd get some nice, forgiving O1 and just futz around. Experiment not only with knife styles, but with the grind, your method of heating, your quench oil, tempering temp, etc.

I've recently made my first 3 knives, so what the hell am I talking about, right? But I found a lot of learning opportunities in sort of winging it a little. Making mistakes is, in my experience, the best way to ingrain things you don't want to repeat. I had to heat treat my first blade THREE times before I realized that the hardening temp had been too low (I was trying to judge it by eye.)

If I had used a computer controlled kiln, would it have turned out right the first time? Sure! But I would have missed the opportunity to learn from that mistake.

Just my humble opinion, one noob to another :)
 

Doug Lester

Well-Known Member
Mook, you make a good point but there are those smiths and grinders who question how forgiving O-1 is. Of course that just an opinion, and like skin moles, just about everyone has a few. Personally, I try to stear beginners away from 1095 because it can be a little tricky to harden and I've read some posts from master knifemakers who've given up on it for that reason. Myself, I've had both good and bad luck with it and have moved on to 9260 and I have a few bars of 52100 that I'm going to get around to trying one of these days.

Doug Lester
 

Josh Dabney

Moderator
Doug, thanks for the tip on Verhoven's book. It's been added to my must have list LOL
"You still need to austinize the steel before you can normalize and 1095 is still shallow hardening" Can you further explain this statement ?

Here was my understanding -

1st normalizing heat 1475* which is past austinizing temp. (and should put enough carbon in solution for full hardening)

2nd & 3rd normalizing heats are sub-critical to refine grain structure

Mook- I do undertand where your comming from. Although still a complete newb judging by # of knives actually completed I have been a dedicated study of knifemaking for a year now. I have made a few knives from O1 but I'm looking at making some knives to target cowboy action shooters and want to stick with plain carbon steel for this demographic. Now I could stick with 1080 or 1084 but where is the challenge in that ? LOL. Actually I'm not doing any yet but plan on doing some forging in the future and seems to me like Aldo's 1084 is a hard steel to beat so I'm not stuck on 1095 forever but I am going to give it a shot.

I'm currently working on my 6th knife which is a 6" light bowie/fighter with a full height flat grind and clip point with a swedged clip. It's also a tapered tang and distal tapered about half the blade length with some simple but attractive filework and an edge quench. Not exacly beginner geometry by any means but the symetry of the grinds is FANTASTIC ! I'm very proud of this grind and feel it takes most beginners much longer to get a grind this even especially grinding freehand.

Not trying to toot my own horn here as I still have a long long way to go and won't at all be surpized if the next one ends up in the trash before making it to heat treat, LOL. I just wanted to explain where I'm at personally with my knifemaking endeavors.

Great discussion here everyone. Thanks again for helping me understand the ins and outs of 1095, Josh
 
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Sean Cochran

Well-Known Member
Josh
I still say you are spot on. 1095 is not that difficult, you just have to make sure the quench is fast. Like I said I have been using the same basic recipe that you have (minus the cryo) and have had great results. I am using 11 sec oil and it works fine. I also remember seeing a thread on here a couple of weeks ago about someone using room temp water without cracking alot of blades. I havent been brave enough to try it yet my self.

Sean
 

Doug Lester

Well-Known Member
Just reinterating comments that I made earlier. Normalization relies on the phase change from from the face centered crystal (austinite) to the body centered crystal at normal cooling rates (I wonder if that's where the normal in normalization comes from). The second part is that 1095 is still 1095 and martempering is not going to change it's characteristics for the good or bad.

I thought that my comment on 1095 was going to get me into it. Is 1095 a good blade steel? Yes, but it's not the easiest to heat treat and it is possible to over refine the grain and come up with a blade that will never be able to hold an edge. Many custom knife makers and manufactures of knives use 1095 but it's not the easiest steel to start out with.

Most of us find one, two, or maybe three steels that we can work and stick with them for good, bad, or indifferent reasions. We learn how to work them and we stick with them. Does that mean that we are using the best steel? No, we aren't even necessarily using the best steels for us; we just stop reinventing the wheel. My decision not to use 1095 is due to problems that I had in heat treating and that I find that 9260 forges a little better and heat treats easier.

Doug Lester
 

Josh Dabney

Moderator
Thanks for the clarification Doug, I thought I was missing something for a minute there. I think I got a very good staring point for 1095 thanks to you guys.

Thought I'd post a couple pics of the blade I'm currently working on just to see what yall think.






Thanks again for all the help guys, Josh
 
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