More on heat treating

Laredo7mm

Laredo7mm

Joined
Jul 8, 2002
Messages
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As you all might know, I work with 1095 and 15N20 damascus. I have just started an experiment for different heat treating methods to refine the grain and produce martensite. This is starting out simple, but I can see it becoming very complex before too long, there are sooooo many variables.

Right now I am doing my testing with plain C1095, not with the damascus. It has been pretty difficult to find the correct info like continuous cooling transformation curves and Isothermal transformation curves, so I have just started testing to see what happens. If any of you have or know where I can get CCT's ITT's or TTT's please let me know.


This is what I have done so far:

Three samples of 1095 that are .125 x 1.00 x 6.5
All three samples where soaked for one hour at 1525 deg F before any processes were started to try to get some grain growth.

Sample #1 went through 3 thermal cycles before being quenched. Each thermal cycle consisted of removing the sample from the oven and cooling it rapidly in air. After the air cool, it was placed back in the oven.

Sample #2 was triple quenched.

Sample #3 sat in the 1525 deg oven for 1.5 hours and was then quenched

All samples were quenched in 80 deg oil. The oil is a 50/50 mix of 10W30 and ATF. After the quench, they were allowed to cool to room temp and were then placed in the freezer for 9 hours. Interestinly I found out that steel with over 0.6% carbon will not completely tranform to martensite unless cooled to less than room temp.


The resultsto this point:

Sample #1 - 64 HRC
Sample #2 - 63 HRC
Sample #3 - 63 HRC

The next step is to temper all the samples at 350 deg for 2.5 hours and retest for hardness. The tempering will continue until a hardness of 58-59 HRC is met. Then I am going to either tensile test or try to do a bend test to find out if there is a difference in the "tuffness" of the blades.

Let me know what you all think about this, and if you want to see the further results. I don't know if 1525 is a high enough temp to grow grain or not. What I want to do in the near future is some marquencing and see how that works out. If the marquenching turns out well, I think I am going to go in that direction, since it is less stressfull on the steel during the quench.

Anyway, let me know if you all want to see more of my results as they become available.
 
Laredo77, I'm just starting out and using 5160 for my teething steel. I have been doing a lot of research and plan on doing my own testing in the future as well. I for one, love to read this kind of thread as it gives me ideas for my own testing. We might be using different steels but I'm sure I can gleen something from what you are doing. Keep it comming.

Thanks for sharing! Knowledge is power!

Rick
 
thermal cycling at 1400F with a soak of about 2mins will have good results.
You can austenize for quench the same, but I suggest an interuption on the thinner stuff.
Austenizing at 1400 will cause things to harden deeper. good for thicker stuff.

Joe Renner
 
Yes, these sorts of posts are great. Your approach is solid, but why stick with 1095? I feel you are making things unnecessarily hard for yourself. Even the added manganese in 1084 will make things a bit easier on you.

Your quenching oil is probably a bit cool, too. Try around 120-160F. It is a bit counterintuitive, but warmer oil (to a point) cools steel faster. Cooler oil is too viscous to effectively transfer heat. But your steel is getting plenty hard, so....

As for marquenching, 1095 is also not an ideal candidate. Steels like L6, O1, 5160, and 52100 have enough alloying elements to increase hardenability to a point where marquenching works well. With 1095, a steel with very low hardenability, you may get less than optimum results. Hardness, which you are obviously getting, is a very different thing than hardenability.

On the other hand, if you are going from high temp salts to low temp salts you may be able to bring the blade to near finished dimensions prior to the hardening operation. If it is quite thin, you may be successful. Still, be ready for a distinct hardening line (hamon) somewhere on the blade.

John
 
how do you guys test the hardness of a blade? is there a tool that you apply to steel to determine the hardness?

im assuming you are fully quenching the entire blades?
 
we have a hardness tester at my work, one of those fancy $16,000 jobs, we also have a tinious Olsen tensile tester, but would rather bend them till they broke.

I am ht just rectangular pieces of steel for this test.

Yeah, I agree thatmy oil temp was too low, it was better than the 46 deg it started at:) I just got impatient waiting for it to come up to temp, I wanted 100 deg, oh well, next time.

Why just 1095? The only thing i have done so far is 1095 with 15N20, I love the contrast between these two steels, but instead of testing the damascus, I am just going to test the plain 1095. I can't help it I am lazy:D

I agree that the hardenability of the 1095 is less than desireable, it would be nice to have more than 1 second to get past the nose of the TTT curve, one of these days I will branch out to different steels, if the damascus bug ever goes away.;)
 
Its not the steels time to get under the nose as much as your ability to manipulate lots of factors.
 
I agree with Joe. Time and temp, time and temp, time and temp.

I'll stick my neck out a bit and say that properly treated 1095 is great steel :)

Nick
 
Keep on, keeping on, Sean. I think your oil temp is a might to low, try 140%. I use alot of 1095 and that is where I am getting the best results. 1095 is one great steel and can reach 59 RC, when properly
heattreated. Great thread, would truly enjoy seeing more of the same.
Ken (wwjd)
Someone piss you off in PT, you do not come around much?:(
 
hey Ken,

No nobody pissed me off. I am still getting viruses, and I think it is from being logged on to PT. So I have been logging on and not really going to any specific rooms, just to see what happens. Caught another one today when I ran my virus protection. I run it everyday now, and I usually catch find something every week. Hey, maybe I am geting them from the forums:)

Plus work is kicking my butt, I have a new program launching right now so it is going to be realy busy unitl the end of summer. Especially starting in April.

Anyway, I will be back in PT soon to check up on you guys. Talk to you later buddy.
 
I agree with Nick and Ken--1095 can be a great steel. I was just trying to suggest some easier alternatives. Bottom line is if you like working with it, you can make it work.

Have fun,

John
 
Originally posted by NickWheeler
Time and temp, time and temp, time and temp.
Click to expand...
I love hearing that! Very true, too.
Being good at the little things is what sets the serious apart from the hobbyist.
 
Sorry John, I wasn't meaning to be snotty about that or anything.

There are so many variables in heat-treating, I admire the desire here to narrow some of them down.

I spent the end of November and all of December testing. I ended up testing 25 knives to destruction in that time. Plus about 25 test pieces that were just barstock.

That was 50 times to make me realize just how little I know :)

Out of those, the 1095 blades were given multiple normalizing cycles....starting at 1550F and working down to 1400 in 25 degree increments. Fully hardened blades were soaked at 1450 for 4 minutes and the differentially hardened blades were austenitized at 1535. All except 2 of the 1095 blades were quenched in Tough Quench.

They had extremely fine grain, showed very good toughness, and cut very well.

Hope this helps :)
Nick
 
Just an update:

I tempered the three samples and did another HRC test. The samples were drawn twice at 350 deg for 1.5 hour. Here are the results:

Sample #1 - 59
Sample #2 - 59
Sample #3 - 59

I am still trying to figure out a way to test the tuffness and quantify the results. If you all have any ideas, I would like to hear them.
 
Good to see more results here. I suppose the tests depend on what sort of "toughness" you are looking to guage. Toughness is a general term, used differently by different people. In most books on metallurgy it is the ability to resist complete breakage. IOW, a blade can bend very easily and still be considered very tough. Strength, on the other hand, is the ability to resist deformation. IOW, a blade can be extremely strong, but still break if it is bent to say 25 degrees.

So, are you testing impact toughness (hammer suggestion might apply here) or resistance to breakage when flexed (a vise and cheater pipe would apply here)?

John
 
Laredo,
Some ideas to take from:

This may sound crude, but for toughness I cut into steel plumbing pipe to judge some things. (Not for silly visual effects, mind you ;) ) The material is harder than what the blade will cut in service usually, but mostly just serves as a simple benchmark. Also, the pipe steel is soft enough to let the edge bite, so, I can see how deep different profiles can cut but still resist wedging themselves. Okay these are for tanto's but hey, its an idea to play with. :p

I used to do a lot of flex tests, but they only tell you so much and you get the idea after destroying too many blades to count. I.e. size, weight, HT, sharp, not sharp, sharp bare jaws, smoothed jaws, etc. So these days I mostly test edges. I test edge retention by judging its sharpening on the grinder, stropping and subsequent paper cutting, shave test, etc.

The pipe test also give me a rough order of magnitude, as to how much the edge dulls in these toughness tests. And since I'm really mean to those nice, super keen fully convex blade/edges, well you get the idea, pipes and paper for me. Just works. :cool:
 
What I am thinking is doing a bending test to failure. Either a simply supported beam test or a cantilever test. The simply supported beam test would be with each end of the test bar supported and push in the middle until the bar breaks. The cavilever test would basically be the bar in a vise and bend it with a cheater pipe until the bar breaks.

I have had pretty good luck at work with the access to the hardness tester, but we don't test any force vs. deflection on the small scale I am looking for in a bending test. We do however do tensile testing. I could have these samples pulled until failure.

What I am looking to findout in the test is the sample's strength or how hard it is to break or pull apart. Since I did two different thermal cycles, and one without any, I am hoping to see a difference in the failure points of the three samples. Hopefully, that would correlate to grain size/refinement.

If I do a pull test, I can get a force versus deflection curve and therefore the energy required to break the bar. If I do one of the bending tests, I can choose either deflection, force, or angle, but I can't have them all since I will be doing the test with equipment i make myself and there is no room in the budget for fancy data aquistion stuff:)

One other bonus from work today, well two. We can do microhardness testing where the lab tech encases the sample in epoxy, polishes it and then does a hrc test (it is supposed to mor accurate). He can then thake that polished sample and etch and take pictures of it under the microscope and tell me what percentage of martensite, perlite, banite, etc there is in the sample. Pretty frickin sweet.:eek:

Oh yeah, I guess there were three bonus's today. I talked with my QE and he is going to fill out a release of assets form for me. If everything goes good, I should inherit an AMES portable hardness tester:D It may not be as accurate as the big machines, but it will be alot easier to do this at home than at work.

Let me know what test you all think would tell me the most about the grain size. Thanks for all your help.

-Sean
 
Laredo
Great thread :D
Thanks for sharing your findings, my Fav is 5160 but I am about to try a bar of 1095. Doing stock removal. Really interested in how the toughness and flex test come out.
Way to go!!!
 
Laredo7mm, I consider that last post just plain rubbin' it in!:mad: ;) That's an incredible opportunity that you have. I'm sure that I'm speaking for a lot of us when I say...I wish I had access to that kind of equipment!
The cantilever test seems more of a real world test than the tensile strength test (as far as knives are concerned). But I guess either test would give you something to think about. Would there be any way to get a measurement of force on the cantilever test?
 
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