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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #31  
Old 01-30-2016, 11:59 AM
samuraistuart samuraistuart is offline
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David, heat treat houses and professional knife makers (I would say 95-97%) warm the kiln to the target temp first, let the kiln equalize, and then place the blade in. The faster the heat rate on the low alloy steels....the better. Why that is....I was told but do not recall. It does have something to do with keeping the microstructure of the steel as tight as possible, IIRC. If you want to do otherwise.....your call. But it is not the normal, or best, way to do it. Kiln overshooting target temp being a BAD BAD thing to happen to a blade that's already IN the kiln.

2. I will say this about canola and 1095. It is not the best quenchant for such a shallow hardening steel. You may know that already. I used it extensively and it works well. You will not likely reach max hardness or full hardness, especially on thicker stock. When I got the Parks 50 oil, the results were much better, easily noticeable. So off the bat....canola is a compromise. And you seem so concerned about the extra minute or two a blade takes to warm up.....and you've already compromised on one of the most important aspects of the heat treat......proper quench oil. But I get it....if you're trying this out and you're not getting into it....then canola oil will work for you.

As far as the quench methods.....yes whatever works for you. There will be NO....ZERO....NONE.....difference in the final product using your three methods. They will be identical in the end after tempering. There is SOME.....read VERY VERY little....auto tempering that can occur if taken out and left to air cool after the peralite nose has been beaten. Every single knife I make, from hunter to chef's knife, I take it out after a slow 7 count, check for straigtness and straighten if needed as Ms-Mf is reached, and then back into oil until room temp. Some guys will do any and all straightening during the temper. But, again, you can believe me or not, but there is NO difference at all in the final product. If you would rather hear that from a metallurgist, I invite you to go to hypefreeblades and search for a thread, I believe I started it, asking the exact same question about leave in oil vs air cool after PN reached. Kevin answered.

Again, your two questions about kiln hot vs cold and quench procedure....I had the exact same questions. and Kevin answered them for me....and I repeated those answers to you. I have some understanding of this....but not like Kevin. He can rattle stuff of the top of his head that is just amazing.

3. As far as anti scale....I would just get a quart of ATP-641. Advanced Technical Products. they'll send it to you and then bill you.
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  #32  
Old 01-30-2016, 01:07 PM
samuraistuart samuraistuart is offline
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Actually the thread I was referencing was at KnifeDogs. Not Hypefree.

The thread was titled "To leave it in or not to leave it in". Kevin's last statement about toughness is in reference to full on marquenching, which is not what we are discussing here, but the mechanics translate directly....

"Marquenching/martempering has been around for, oh… around a century or so, in industry, but knifemakers still struggle with the concept and there is a lot of misunderstanding about what happens. You could take the other sources word for it, or you could take my word for it, I strongly advise you do neither but instead rely on solid information and verifiable data on the topic. I have been playing with marquenching for around 20 years now and have also been testing and slicing up steel for metallography work on the products of that process for about as long. If done correctly there is not hardness loss in the martensite formed, just different HRC readings due to auto-tempering.

Under the microscope I could show this clearly. An older text used the terms “alpha martensite” and “beta martensite” and I always liked the differentiation the terms lend to the discussion. Alpha martensite is as-quenched, it is body centered tetragonal in nature as it retains all the dissolved carbon of the parent austenite; it is typically from 65HRC to 67HRC in hardness. Beta martensite is alpha martensite that has been tempered, it is more body centered cubic in nature and has less carbon in solution than the parent austenite because the process of tempering has formed ultra-fine tempering carbides from the excess solution. The accumulative effect of the tempering carbides is a darkening of the martensitic packets (be it laths or plates, but mostly plates for this discussion); so beta martensite is darker under the microscope and is naturally softer because it has been tempered, so its hardness will be a range that depends in the tempering temperature.

Steel that is quenched all the way to ambient in the oil will be all alpha martensite and so will show the maximum as-quenched hardness. Steel that is allowed to air cool from Ms will also form alpha martensite but as much as 30-40% of the alpha martensite will form at temperatures well within the tempering range and will have time for those temperatures to begin the tempering process. So under the microscope you will see both alpha and beta martensite in marquenched steel. Both steels made the same phase, alpha martensite, just one has had the time to convert some to beta martensite and get a jump start on the tempering process. So while one will typically read about 1.5 to 2 points lower in the as-quenched Rockwell, this is only because one hasn’t seen any tempering yet and will join its partner as soon as it does. So in actuality there is no loss of as quenched hardness just a difference in degrees of subsequent tempering. If the quench was sufficient to get past the pearlite transformation to Ms at the appropriate rate there will be no other phases from the parent austenite other than the martensite, upper bainite can form in minutes but lower bainite takes much greater time and simple air cooling is too quick, so a proper marquench will not involve any austempering processes.

But there are other differences worth noting. Plate martensites impinge its packets at high angle orientations and can lead to embrittlement and micro-fractures of the martensitic plates, and while this can be alleviated somewhat by limiting grain size the effect of carbon over .6% on martensite is still there. The martensitic transformation is shear driven, not diffusional like other phases, so it involves tremendous strain on the steel’s crystalline lattice, the more violent this transformation, the more stress will be involved, increasing brittle type behavior. The slower rate of cooling from Ms not only reduces the stress issues but it also allows for the elimination of some of the strain related problems by a quicker conversion (at least partially) from the body centered tetragonal morphology. This results in less distortion and cracking issues but can also lead to an increase in subsequent impact toughness. My friend Tim Zowada was using marquenching even before I was and took time take samples to a lab for more thorough impact testing, and found he gained around 20% impact strength from the marquenching of O-1 over that quenched to ambient. I have also read research that cites even higher toughness numbers from the process but I am more cautious with numbers over 20% even when provided from a proper scientific study.

So after all that I can say- no, you lose no hardness from the marquenching method, you just gain some initial tempering effects, but you do stand to gain some impact toughness from the process over traditionally quenched steel. " -Kevin Cashen.
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  #33  
Old 01-30-2016, 02:17 PM
David Eye David Eye is offline
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Stuart, thanks a ton for all the great info and for taking the time to explain everything.
Also, thank you for forwarding K. Cashen's info.....very appreciated. I am also very happy to hear you had some of the same concerns and questions in the past, also obviously answered by Kevin.

Additionally:
1) I will have to try the Canola oil and yes I know it's not the best. I just won't be spending that kind of money YET on Parks 50. I know 1095 is a shallow hardening steel and Canola is not optimum, but from what I read, if true, it is only about 2 points lower than Canola. Time will tell how I like it. I'm using 5/32" 1095 for my hunting knives even though 1/8" would do OK. My bevel grinds will be going fairly high up the blade and I will be doing some minor grinding on the other areas of the knife that will stay thick. So, actually the thickest parts of my knife will be something less than 5/32", plus I am most concerned about the hardness of the majority of the blade portion anyway. I'm hoping that my knife's spine hardness above blade will be plenty deep especially being something less than 5/32". I'm not real concerned about the handle area.
I AM NO LONGER SO CONCERNED ABOUT WHICH QUENCH METHOD TO USE, Kevin's info has me convinced, (thanks for including it).

2) I agree that ATP641 would be one of the best choices for an anti-scale/decarb coating. Again, I am attempting to cut corners in an area that I feel isn't quite as critical as others since I will be doing some final grinding/sanding anyway. I would love to be able to use a less expensive locally purchased alternative. Therefore, I will be experimenting with the home brew coatings I listed previously. I would like to hear from people that have tried some of the things I listed and how they rate them.

3) Lastly, pre-heat oven or not issue. I hear you and believe you, but everyone's electric kiln is not the same....especially home built units like mine will be. Has anyone tried my alternative compromise method? Can they make an experienced factual statement regarding the outcome? I intend to build my kiln with the proper wattage for compartment size and insulating properties, but I am still skeptical about being SURE or not if the knife will be fully saturated to 1475F IF my kiln only takes 2 or 3 minutes to rebound (which remains to be seen). With my compromise, I'm HOPING my knife won't be in the kiln terribly long anyway.....I'm guessing at 5-15 minutes longer if I put it in at approx. 1000F before the soak, but this I won't know until I cycle my home made kiln. There are too many "ifs" right now regarding my kiln.....time will tell. If I end up finding that my home built kiln rebounds very quickly I will probably try the method you suggest. As far as concerns about overshooting the target temp......I would think that is always a concern when a 10 minute soak is required anyway. I will have a very good TC and controller plus I don't think I have to worry unless the knife gets above about 1525F. Please enlighten me further on this point if you feel I'm off base. I am aware that the actual blade temp can be slightly different than the air by the TC.

Thanks again, your info and thoughts are very appreciated along with your time, effort and patience.
DAVID
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  #34  
Old 01-30-2016, 07:49 PM
David Eye David Eye is offline
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For anyone interested, I finally found some more info on Milk of Magnesia.

Milk of Magnesia is magnesium hydroxide, MgOH2 The standard original formula Milk of Magnesia.
Magnesium hydroxide is magnesium oxide, MgO combined with water.

When magnesium hydroxide is heated to over 660F it decomposes to magnesium oxide and releases the
H2O (water) and is then a refractory with a melting point of 5000F.

I read somewhere else weeks ago that someone was using it as an anti-scale/decarb coating for knives.
I don't know if they were using it in an electric kiln or not.
I'm strongly considering giving it a try. I would probably put 2 coats on depending on the viscosity and let it dry first. Of course, I will clean the knife blade very well first.
It just might work and be a heck of a lot easier and cheaper to obtain.
As I stated earlier, some people have used white paint markers, dissolved chalk, Ivory soap or even high temp header paint (harder to get off).
I know ATP641 is good proven stuff as is Satanite, but ATP641 is about $15/pint + plus shipping.
I definitely will be trying good old original formula (not flavored) Milk of Magnesia for $2-3 from Wally World on some scrap pieces.
Am I cheap?, sometimes out of necessity. Am I frugal?, almost always. Do I like the thought of something so inexpensive, locally available and MIGHT work as an anti-scale/decarb coating?, definitely!
Trouble is, I won't be able to try it until closer to Spring. My elect. kiln won't be finished until then......just too cold out in my unheated pole shed/shop!
DAVID
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  #35  
Old 02-01-2016, 08:16 AM
Kevin R. Cashen Kevin R. Cashen is offline
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My name has been invoked more than 3 times so I am now obligated to wreak havoc, death and destruction and collect any souls for the taking… just kidding, Stuart and Doug, you are doing great and not only do I not have much spare time to contribute a lot, I don’t need to, there is little more for me to add.

I don’t have the moments it would take to read the entire thread but I would like to point out that I strongly recommend 1475F for 1095 with lesser soaks. There are worst things out there than even enlarged grain. With most carbon steels it is not as much a matter of if a soak is hazardous as much as it is a question of whether it is even necessary. I found a grain coarsening temperature for one batch of 1084 at around 1525F but I was intentionally looking for trouble, but with some of the things that can go south with 1095 I don’t go looking for trouble and so I keep the temp at 1475F and keep the soak limited to 10 minutes or less.

Good luck, but now I need to get back at it….
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  #36  
Old 02-01-2016, 10:00 AM
David Eye David Eye is offline
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Kevin, I know you are a very busy man and I really appreciate you taking the time to post with info.
Obviously your expertise and input is highly valued by many including me. I have used much of your past input in my research and decision making.

I have been planning on a temp of 1475F and a soak of no longer than 10 minutes.
My main question and concern is regarding "when" to put my blade in the oven and still not have to worry about it being at temps lower than 1475F.

1)The method strongly suggested to me is to put the blade in after the elect. kiln reaches 1475F and then let the oven rebound to 1475F and then soak for no more than 10 minutes. Since my home made kiln is not finished yet and out of my ignorance, I was concerned that my knife may or may not be completely saturated to 1475F in the very short time it MIGHT take my kiln to rebound to 1475F. The blade MIGHT be only at 1400 or 1450F or even less in just those few short minutes in my mind, but I could be completely wrong. If I'm not wrong, then using this method might only (in actuality) involve a shorter soak of just a couple minutes depending on how long it actually took the blade to get to 1475F. Many people apparently are achieving success with 1095 this way, even IF their soak is something less than 10 minutes @1475F.
I just don't like "ifs" and "maybes" if they can be avoided.

2) My alternative was to put my knife in the kiln at maybe 1000F or even 1200F to give the knife a little more time (exact time unknown, but probably short) to make sure the knife is actually 1475F before the timed soak. I may very well be concerned when I needn't be, but I just wasn't sure the knife itself would be at 1475F after just a possible few minutes of kiln rebound time with the first method. Obviously I have no experience with rebound times for properly built kilns....homemade or not. I'm just going by what other's have said that it is only a few minutes for the kiln to rebound and thus my concern if the knife is really up to temp (1475F) in that short of time.

I had read one of your past postings that at one time you had found that extended soaks at 1475F with 1095 did not cause any grain growth and that we shouldn't worry about that until 1500-1525F......if I understood your posting correctly. There seems to be a concern by others that even at lower temps than 1475F with 1095 there might be a possibility of some kind of "microstructure" negative change, therefore I should not put the 1095 knife in a cold kiln......always pre-heat kiln.

I'm not attempting to reinvent the wheel here. My plan was to just put the knife in the kiln a little sooner, like I said at maybe 1000-1200F for some assurance that the knife will have enough time to truly be up to temp before I start the timed soak of 10 minutes or slightly less.
If someone such as yourself, Kevin, knows for sure that this method will cause harm or microstructure damage at these lower temps or at least have a strong potential.....then I won't attempt it.
If my worries about the blade being up to temp in the few minutes of kiln rebound time are completely unfounded and totally unnecessary......please straighten me out and say so! Other's have said the few minutes of "kiln rebound time" is all the blade needs to get up to temp but they have no proof of that other than a hard blade. Maybe that's good enough, but maybe they hardened because they only reached the lower austenizing temp in those few minutes and were really at 1475F for only a minute or two instead of 6, 8 or 10 minutes. Maybe it doesn't really matter, but for my peace of mind and some assurance......I would like to know.

All the other basic aspects of heat treating 1095 I am "up to speed on" with everyone's help and have no questions on right now. I realize you may not have time to attend to this question and I perfectly understand. If you answered everybody's individual questions you would not have time for anything else. I just can't seem to find a definitive answer so far to my POSSIBLE concern.
Thanks for posting at all to my thread, it is greatly appreciated.
DAVID
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  #37  
Old 02-01-2016, 12:24 PM
Doug Lester Doug Lester is offline
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David, one thing that you have to keep in mind is that there is more going on with temperature than grain growth. There is also carbon solution which can lead to retained austenite. As far as getting the carbon into solution goes it's pretty straight forward with 1095 being that it's a 10XX series steel. It's primarily iron, manganese, a little aluminum used to deoxidize the steel, and a few trace metals and other elements that are impossible to completely eliminate from the melt. The vast majority of carbides in 1095 is cementite (iron carbide) and it gives up it's carbon quickly do it doesn't take a long soak.

Grain growth is a little bit of a boogie man here. No, you really don't want it any more than you can avoid it but you also don't want to get carried away with it either. Smiths, like me, need to correct for it because we routinely take the steel way above the austenization temperature to forge the blades. There is also an attitude around that smaller is better as far as grain size goes. It's not, especially when dealing with 10XX series steels. The finer the grain the less the hardenability of the steel. This can lead to the "auto-hamon" with shallow hardening steels. It can also, taken to an extreme, lead to a situation where only a thin edge or corner of an edge converts to martensite and the hardened steel in a blade is ground away with the secondary grind.

You also need to consider what is gained by getting just a little bit finer grain. The answer is really not much. A lot finer grain? That's another story.

Doug


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  #38  
Old 02-01-2016, 01:03 PM
David Eye David Eye is offline
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Doug, thanks as usual for the info.
About 70% of what you stated I realized....I will keep all of it in mind, but I'm still undecided. I really don't think the small amount of extra time AT THE LOWER TEMPS I'm referring to should do any harm. This is just my opinion and obviously not based on experience, therefore I could be wrong and possibly not understanding something completely.

The basic question I attempted to qualify in my recent reply to Kevin is still something I would like to find out more about if at all possible. Ideally a yes or no would be nice. The little extra time at lower temps will either be detrimental to 1095 or it won't. Like I said, maybe I shouldn't worry so much about this last "method" question, it might even be unfounded, but I guess my stubborn rather exacting nature still needs some peace of mind.
Thanks for your patience on this last issue for me, but I'm still unsure about my alternative method or if there might be a need for it or not. I could always just use the method/timing that most others have used for 1095 and not worry if my method might be even better, it's just a thought and concern I have that makes me wonder and I need to be set straight!
Thanks, DAVID
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  #39  
Old 02-02-2016, 11:32 AM
samuraistuart samuraistuart is offline
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David, your concern with the soak time can be mitigated with a simple coupon test. Go ahead and warm your kiln up to 1475. Take a piece of steel the same thickness as your knife would be, and put it in the kiln, and let it warm up to 1414 (non magnetic). You can use your magnet to test this out. Pull the piece out....check the magnet....still sticks....back in. Do this quickly...no lolly gaggin around. Once the magnet stops sticking, you've reached approx 1414f. Just note how long that took. You would have to guess as to how long it would take to go from 1414 to 1475, which would be in the order of less than one minute. But that can get you very very close as to how long it takes your blade to come up to 1475.
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  #40  
Old 02-02-2016, 01:03 PM
David Eye David Eye is offline
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Thanks Stuart, believe it or not I had already thought of doing my own testing to attempt to find out how long it approx. might take my knife to actually reach 1475F by comparing "times" to reach a lower x temp from a known for sure temp. Your way of using 1414F (non-magnetic) would be a good way to get me a close approximation of time.

I was just hoping to avoid doing the testing by having someone tell me for sure if putting my knife in a 1000-1200F (I might even try 1300F) oven and heating the blade up to 1475F and then do a 6-8 minute soak would do any detrimental things to 1095 or not. If, as most people are telling me here, it only takes a few minutes to completely heat a cold blade just during "rebound" to 1475F.......my way should probably only add 2 or 3 minutes additional. At temps below 1475F how could that really hurt for such a short amount of time?

I obviously don't have any experience heating knife blades in an electric kiln, and as I said my concern may very well be unfounded and definitely ignorant. Maybe it does just take the few minutes of "rebound time" from 1475F to thoroughly heat the knife before the soak as many have said. To put it more simply, I just want to be sure of that, thus maybe the need for testing.
Please keep in mind that I have been getting contradictory info from various sources regarding preheated elect. kiln versus not preheated, including from manufacturers of elect. knife kilns. This type of non congruent info has helped raise this one doubt/concern regarding making sure the knife is up to temp BEFORE the soak.

I personally, from my research so far, just don't think that it will hurt 1095 by using my method of putting the knife in a 1000-1300F kiln and heating it up to 1475F from there will do any damage. So far I haven't found any real proof that it does or can. It might be that my idea of doing it this way is completely unnecessary and a waste of time, but at the same time I haven't found anything stating it can do any harm either.
Therefore, maybe I could attempt to check the temp of the blade right when the kiln has rebounded to 1475F to see how close to 1475F the knife actually is. I really don't have an easy way to do that with the equipment I own. So if I do some testing, I guess I will attempt the other testing method mentioned and suggested.

Thanks to everyone for being so patient with me.
DAVID
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  #41  
Old 02-02-2016, 03:50 PM
Kevin R. Cashen Kevin R. Cashen is offline
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Here is what I do- set the oven to 1475F, let it equalize until it is holding the temp within less than 5 degrees, and then introduce the blade. The oven will drop and I watch until the rebound reads that target temperature again and then begin my soak count.

*O.K. so this is not exactly what I do, what I actually do is place the blade in the 1475F molten salts and the wait for the rebound. As soon as the readout says 1475F again, I start my timer for the soak.

This is with standard spheroidized stock, if I am doing something that requires the elimination of soak time, like heat treating with a forge, I normalize or cycle the steel to put it into a fine pearlitic condition first.
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  #42  
Old 02-02-2016, 04:25 PM
David Eye David Eye is offline
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Kevin, thanks for taking the time with more input.
If I understand you correctly..... I should just put my CRA 1095 knife in a 1475F (equalized) kiln and wait for the kiln to rebound to 1475F and then soak for desired time?

Being new to this and partially ignorant, I do not yet know what "spheroidized stock" is for sure....(is it steel in a fine pearlitic condition?). I can research that term and figure it out soon if need be. Is CRA 1095 standard spheroidized stock? Should I be using molten salts for best results?

Am I to assume (which I hate to do), that you either do not see a need for me to introduce my blade to the kiln at 1000-1300F and/or it could possibly be detrimental to 1095 in some way?

I know you're busy and don't have much time so short and simple answers would be just fine.
Short clarification would be greatly appreciated by me and probably others if and when you can.

Thanks, DAVID
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  #43  
Old 02-03-2016, 01:16 AM
Doug Lester Doug Lester is offline
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Spheroidozed steel is steel that has been heat treated to distribute the carbides in small spheres. Notice that Kevin said "standard spheroidized stock". Most is going to come that way. Some suppliers will even state the percentage of spheroidization.

A molten salt pot gives more heat control than an oven because the molten salts will transmit heat better than hot air and there's no such thing as too much heat control when it comes to heat treating. However, there is a down side to them. They are more dangerous to use. If you are not careful about how you heat them up you can end up with a face full of molten salts at over 1000°. A stainless steel rod, preferably tapered, will help prevent this. I also remember someone stating that fumes from the salt pots can accelerate rusting of steel tools in the shop.

If you google molten salt pots I'm sure that you'll come across some discussions.

Doug


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  #44  
Old 02-03-2016, 08:57 AM
David Eye David Eye is offline
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Thanks Doug......again!
Appreciate the explanation of standard spheroidized stock.
I knew what the use of molten salts was for and I do NOT want to use them, I just wondered what Kevin had to say about the "necessity" of using them on CRA 1095.
I know some people use just plain sand during the tempering process in cheap toaster ovens to help the knife stay at temp due to the toaster ovens cycling at too large a temp variance. I heard you can also put a couple bricks in the toaster oven to help absorb some heat in order to help keep the heat in the cheap toaster oven more even and controlled.

Anyway, back to the elect. HT kiln........
I'm hoping Kevin will have time to answer my very last question regarding putting the knife in the oven at 1000-1300F and whether he sees that as totally unnecessary and/or possibly detrimental to 1095. I guess he probably doesn't see it as necessary or he would be doing it, but then.....he is using molten salts and I will NOT be. As I said, a short simple answer to my question will suffice to save time.
I am now even considering introducing the blade at more like 1300-1400F, I personally don't see how that could really hurt IMO.
Once I get some answers to this, I can finally be done with this thread and leave people alone and stop trying peoples patience. If I can't get answers then I will probably do the temp testing discussed a couple posts back.
DAVID
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  #45  
Old 02-04-2016, 10:48 AM
David Eye David Eye is offline
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I have to say that I finally found a definitive answer to my question on another forum by doing a very exact worded search!
Someone else had the same exact question regarding how do you know for sure the knife is actually up to temp in the few minutes in might take for the elect. kiln to rebound to set temp.

Two separate experienced guys did some extensive testing to determine actual knife temp readings using non-touch temp devises at various times and also only using the non-magnetic method....they concluded the following:

With high carbon hunter sized knives they found that on average the knife was up to temp in approx. 4 minutes after introducing it to the pre-heated stabilized elect kiln. They always let the elect. kiln stabilize first at set temp before putting knife in, which sometimes took up to 30 minutes which, of course, was dependent on the quality of their elect kiln and also that it just takes time for the bricks, etc. to get up to set temp and stabilize.
They did NOT start the actual soak time until the 4 minutes was up in order to be sure the entire knife was up to temp, even if their kiln reached the set temp in less than 4 minutes.

In conclusion: If my home made electric kiln can rebound to my set temp of 1475F in 4 minutes I should be just fine introducing my hunting sized 1095 knife to the "stabilized" 1475F kiln, wait 4 minutes and then do a 5 to 10 minute soak. As long as the blade does not get over 1500F all should be good.

I think using a stabilized kiln is important, as people here and elsewhere have stated.
Many of you told me that it takes approx. 3-4 minutes for your kiln to rebound but couldn't tell me FOR SURE if the knife was actually up to that temp, but now I know for sure that 4 minutes is enough time for the blade to be completely up to temp IN A WELL MADE "STABILZED" KILN.
My kiln will be well made, insulated and sealed and will be very comparable to a store bought unit. My controller is also of very high quality along with the TC.

Since the type of testing has already been done that I was going to do, I see no need to do it myself for verification and beat a dead horse.
At least I was not alone with my concern, although I am more than willing to admit my concern was somewhat ignorant and ultimately unnecessary. As I stated before, I would rather be safe than sorry and ere on the side of caution since I couldn't fine any definitive answer to my concern about the knife actually reaching full set temp in such a short rebound time......until now.

Thanks again to all for the great help, info, suggestions and much patience.
I do apologize for dragging this on so long.....but I am persistent!
Finally case closed!
DAVID
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