Did I mess it up?

K

Kev

Well-Known Member
I made my first attempt ever at heat treating some 1095. Got it hot, dunked in oil, let it cool down. File glanced off like it was glass, I was pretty stoked.
Put the blade in the oven on 375 for 2 hours. Took it out. Cooled down. Back in 375, 2 more hours. Now the edges of the blade and tang are straw colored! Did I blow it by getting it too hot while I was attempting to temper? I haven't file checked the edge yet, but I was hoping to get some opinions.
Thanks
 
No. Straw is fine. You could drop the temperature times down to one hour each, but you didn't hurt anything.
 
The short answer is no, you didn't "mess it up". Degrees of the "straw" color are the first to appear in the tempering range of temps. In general those colors start at 350F, and the color changes for every 25F degree increase.

There's far more to the "correct" tempering temp/color then just the type of steel. The type of grind, edge geometry, profile, and any number of other factors play into the "correct" tempering temp....in reality it is a "moving target", and can be different, even for different types of blades made from the same steel. Tempering is the one major area where the knowledgeable knifemaker can "tweak" things.

I have to respectfully disagree with dropping tempering time to 1 hour. It CAN work for smaller, thinner blades, but experiments and research have proven to me that blades of 1/4" thickness generally require 2 hours to achieve the full affect of tempering.
 
Personally, straw color is what I shoot for. Sounds like you did just right to me.


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EdCaffreyMS said:
The short answer is no, you didn't "mess it up". Degrees of the "straw" color are the first to appear in the tempering range of temps. In general those colors start at 350F, and the color changes for every 25F degree increase.

There's far more to the "correct" tempering temp/color then just the type of steel. The type of grind, edge geometry, profile, and any number of other factors play into the "correct" tempering temp....in reality it is a "moving target", and can be different, even for different types of blades made from the same steel. Tempering is the one major area where the knowledgeable knifemaker can "tweak" things.

I have to respectfully disagree with dropping tempering time to 1 hour. It CAN work for smaller, thinner blades, but experiments and research have proven to me that blades of 1/4" thickness generally require 2 hours to achieve the full affect of tempering.
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What kind of changes/differences did you see?
 
What kind of changes/differences did you see?
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Because I've administered many JS tests for various people over the years, I am adamant that a single, 1 hour tempering cycle simply does not get the job done. To explain, a number of JS test failures over the years were due to blades breaking on the 90 degree bend test. In the vast majority of those failures, the individuals did one of two things.... 1. Tempered the blade for only 1 hour. 2. Fully hardened the blade, then attempted to do a "soft back draw". Whichever of those methods were used, the results were the same.... upon visual inspection of the broken ends of the blade pieces, it was clearly visible that there was an outer "tempered" zone, while the inner portion was still fully hard. What that means is that the tempering heat was not a long enough duration to covert the steel's matrix all the way through the blade(s).

Further evidence was to grind into a broken piece of the blade(s).... it was obvious that the sparks changed between the time the belt hit the exterior surface, and once the belt ground through the "tempered skin", the spark pattern changed dramatically, indicating the the interior of the blade was harder. It's difficult to get an exact measurement on the actual depth, but in general, on the size blades used for the JS testing (10" camp/chopper style blades, with the thickest part of the spine being in the 1/4" thick range) those blades that where only tempered for 1 hour, had a "tempered skin" of approx. .020-.025".

So what does all that mean? For me it's proof that the two things that are a constant with steel are Time AND Temp..... in order for changes in the steel's matrix to take place, it takes a given temp exposure, for a given amount of time, to achieve a specific outcome. I've also had a number of metallurgy tests done over the years, using different samples of the same steel types, which were tempered at different lengths of time.... from 30 mins, up to 3 hours, and from 1 to 6 times (cycles). Long story short, 2 hours X 3 cycles for the steels that I use gives me the results I desire. For me, and my desires, I suppose the word "optimal" could be used.

I certainly can't state that what I do is "the best", but it's the best FOR ME. In 30 years of Bladesmithing/Knifemaking, the one thing I know for certain is that when you try to take "shortcuts", then you're settling for less then the best you can offer. If you'r not experimenting, testing, and seeking improvement with each blade you make, you're only fooling yourself. Knifemaking in general isn't about the "finish".....it's about "the race".
 
I was actually suggesting Kev use 1 hour tempers instead of 2 hour tempers, but still 2 of them. Was this knife intended to undergo the JS test?
 
Was this knife intended to undergo the JS test?
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I don't believe so, but in my mind that shouldn't matter. I was using the JS testing experiences as a practical reference as to how a person can interpret or "gauge" how the length of temper time can affect a blade. Not fussing, but I got the impression from that comment, that if it wasn't a "test" knife, then it wouldn't matter. To explain, I reach back into my experimenting/experience..... from the aspect of how temp, AND the duration of that temp affect steel, 1 hour tempering cycles simply do not accomplish the same thing(s) as a 2 hour cycles.

It's difficult to explain without showing you the paperwork/reports on many experimental samples of steel, but its sorta like not baking a cake long enough....if you took a cake out of the oven at 1/2 the recommended baking time, and allowed it to cool to room temp, then put it back into the oven for the remainder of the recommended baking time, it simply would not work....the cake would either not be fully "baked", or it would be burnt..... basically it would not come out in it's best edible condition. Of course there are "factors" that could/would affect just how good or bad the cake turned out (I mention that because varying factors are present in everybody's knife shops), but for our purposes, let's just say it would not be the best quality it could be. The situation is similar with steel.

From my viewpoint, I believe it's vitally important that each an every blade a knifemaker lets out of his/her shop, be the very best it can be (for the specific individual's current skill level). Why? It's all about building and maintaining a good reputation, and personal integrity. Just as much as any profession, and maybe even more so with being a Bladesmith/Knifemaker, a good reputation is something that is hard to earn, and very easily lost. I would also hope that any knifemaker would have an inner drive to offer the very best he/she is capable of producing. All it takes it letting one substandard product out the door, and it ending up in the wrong hands. Bad news travels at the speed of sound, and in today's world, hearsay seems to carry more weight then fact.

All that being said, my point/advice is to ALWAYS do the very best you can. The only person you are competing with is the "man in the mirror".....if at the end of the day, you can look in the mirror and honestly say
"I did the very best I was capable of today." then nobody else has anything to say about it. As for me, I certainly do not know it all, nor will I ever. I simply try to share my experiences, and help others not make the mistakes I have in the past. :)
 
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What kind of tests/results did the paperwork/reports show? It's interesting that your advice on tempering is so different from your advice on hardening (2 hours minimum vs. no soak recommended).
 
As I mentioned previously in this thread, it's difficult to explain what the test results/reports show without writing a book. Suffice to say that the two processes are totally different, and accomplish two totally different things. My reason(s) for not recommending soaking (during the hardening process) is because there is a VERY fine line between getting everything into solution, and blowing the grain size way beyond what it should be. In short, the difference is a matter of SECONDS rather then minutes as many seem to be recommending. I can only surmise that the mindset of "if some is good, then more must be better" is why I hear/read of people recommending insanely long soak times such as 15-20 mins. It's obvious to me that many simply take hearsay as fact, and don't do any experimenting/testing of their own.

Tempering is a different animal. There's no concern with grain enlargement, but the desired product is complete conversion. It should be obvious that doesn't occur when I mentioned broken blades that showed obvious "zones" of varying hardness in the cross sections. I'm not out to change anybody's mindset or methodologies, but when asked, I will offer what I have learned/discovered. It's up to each individual whether they use the information to their advantage, or reject it. I always encourage people to experiment/test, and make decisions based on their own findings, and not to take my advice as "gospel". All I try to do is give them information that will lead them to do so.

Edit: I didn't mean to sound "snarky", it's just that I get so many people who want "proof" (which is what I inferred from your use of the word "interesting") of the things I say/recommend, yet they're unwilling to take any initiative to experiment/test the information for themselves. Many seem willing to read a post on a forum and accept it as truth (referring to the extended soak times I often see on forums), but it seems nobody has the drive to actually test the information. As I always tell my students..... What I do/teach is certainly not the only way, nor is it necessarily the "right" way, but it is the way that works for Ed Caffrey. Take whatever information you receive, including from me, with a grain of salt, until you prove or disprove it for yourself.
 
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"My reason(s) for not recommending soaking (during the hardening process) is because there is a VERY fine line between getting everything into solution, and blowing the grain size way beyond what it should be."

My understanding of soak is that it is steel dependent. You wouldn't soak 1095 due to the grain enlargement problem (caveat....does the 1095 have a vanadium count? If so, that changes things). O1 is a different animal, again to my understanding, due to the alloying. The carbides in O1 would pin the grain boundary (the WC and some O1 even has some vanadium as well), and as long as you did not dissolve the Tungsten carbides and vanadium carbides with excessively high heat during the austenitizing, you would not blow the grain at all, even with an extended soak. Do that to 1095, or White steel, and you might very well have enlarged the aus grain.

I've heard it said that if you have control over temperature, then grain growth really isn't too much of an issue, even with plain carbon steels like 1095, but rather putting too much carbon in solution with the extended soak and ending up with a higher level of retained austenite. I've done this myself, holding 1095 coupons at 1475 for short soak, 10 minute, 15 minute, 20 minute, and after a hammer blow checking the aus grain...and by eye each coupon was like gray velvet. No difference detectable by eye, anyway. That was Aldo's 1095 that did have a little bitty tiny vanadium count, tho.

I am also under the impression that tempering is similar. That if given two steels of identical thickness (let's say 1/8"), one being 1084 and one being O7 for example, that the 1084 steel would not need a temper more than an hour, but the O7 due to it's alloying and higher carbon % would need a longer temper, 2 hours for example. IIRC, the Japanese only snap temper their blades....minutes....if that. Understood, of course, they don't have all the answers and are using very old traditions, and very low alloyed steels.
 
If you've experimented/tested all those things to prove or disprove them for yourself, that's great, and it's the behavior I'm seeking to evoke. If we disagree, that's OK, just proves that things don't work exactly the same way in everyone's shops. I'm not trying to prove anything to anyone, just passing along my experience. It's up to each individual to decide if the information is useful or not.

Where I get a bit
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is when somebody does what they read somewhere on the net in relation to blades/heat treating, and then they call me asking "Why didn't XXXX work like they said it would?!" If we were able to eliminate all the variables, then MAYBE it would all work like the books (or like Joe Bag-o-Doughnuts) said it would, but that's simply not the case for the majority.

As I said....
It's up to each individual whether they use the information to their advantage, or reject it. I always encourage people to experiment/test, and make decisions based on their own findings, and not to take my advice as "gospel". All I try to do is give them information that will lead them to do so. Many seem willing to read a post on a forum and accept it as truth (referring to the extended soak times I often see on forums), but it seems nobody has the drive to actually test the information.
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I can't tell if you're use of "My understanding", "I've heard", and "under the impression" were you just being kind, and if so, thanks..... please know I'm in no way offended. I don't do ego, and most of the time simply don't tolerate it from anyone else. We all come at things through the lens of our own experiences, and if a person doesn't have much experience, they will grab onto most anything that is worded to make it sound logical. The trick is to be able to separate the wheat from the chaff, and glean something useful out of it.
 
Ed, you have vastly more experience making and heat treating knives than I do. I am by no means a metallurgist. I don't have my PhD in heat treating...yet! ha ha I'm always learning, and I want that to come thru when discussing opinions that may differ from others. Yes, trying to be kind....always! Thanks for your help on this forum!
 
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