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Steel recommendations?
- Thread starter Mobius1
- Start date
- Joined
- Dec 30, 2018
- Messages
- 267
Have never had an issue plate quenching even with FFG bevels or hollow ground blades
How do you confirm the hardness in the bevel ground area(s)?Have never had an issue plate quenching even with FFG bevels or hollow ground blades
Would you be kind enough to explain your interrupted quench process and what you mean by the 1000 F?I'll probably want to do some testing with oil quenching once I get the Magnacut. I couldn't find a spec sheet on it anywhere, but I assume an interrupted quench at 1000F is what I should shoot for?
I plan to run a few test blanks to see how it compares to a plate quench. I also got thicker stock than I normally work with, so I may also do some practice quenches in similar sized steel to pin down the timing (I usually shoot for interrupting the quench right when the steel stops glowing.).
I understand that most people would rather plate quench, but oil quench is preferable to me if possible, since I don't have to grind the bevels post heat treat.
edit- I read the spec sheet. Oil quench to 1000 F etc. how will u know reached that target temp?
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- Joined
- Dec 30, 2018
- Messages
- 267
I don’t. The same way you test the hardness on bevel ground areas after grinding them. The heat treat protocol is the same on .04” thick pieces and .215” thick pieces I’ve done and tested and left full thickness, heat treated at the same time. Air hardening steels don’t even need a plate quench to reach target hardness levels. A faster quench won’t result in harder blade.How do you confirm the hardness in the bevel ground area(s)?
Would you be kind enough to explain your interrupted quench process and what you mean by the 1000 F?
I am no expert on this, but the way I understand it, is when oil quenching air hardening steels, you not only put a lot of stress on it by doing a full oil quench, but it speeds too quickly through the martensitic formation process (I forget the exact numbers on this, but I believe it begins somewhere below 900F.). So the goal is to quench it in oil past the pearlite temperatures (The 1000F), but pull it out from the oil before it reaches the martensite transformation phase. Then it has plenty of time to transform.
If I am wrong about what is happening exactly, and someone wants to school me on this, I'd actually be grateful.
I don’t. The same way you test the hardness on bevel ground areas after grinding them. The heat treat protocol is the same on .04” thick pieces and .215” thick pieces I’ve done and tested and left full thickness, heat treated at the same time. Air hardening steels don’t even need a plate quench to reach target hardness levels. A faster quench won’t result in harder blade.
Have you actually tested this? Because I have not only seen a difference in hardness between oil/plate quenching of air hardening steels, but also a hardness difference between plate and air only quench. But I guess it can largely depend on the steel in question, too.
But I also wonder if there are other factors, as well, such as grain size differences. Hardness does not tell the whole story. I actually planned to do some more extensive testing a year or so ago (I even made a post about it.), but unfortunately due to health reasons I haven't been able to do anything with it until now. It's always been a bit surprising how little information there is on interrupted oil quenching.
Ultimately, I am in no way trying to say it is superior. I just don't trust plate quenching a beveled blade.
- Joined
- Dec 30, 2018
- Messages
- 267
I don’t oil quench air hardening steels. But I have tested forced air quench and plate quench and got the same hardness on both.I am no expert on this, but the way I understand it, is when oil quenching air hardening steels, you not only put a lot of stress on it by doing a full oil quench, but it speeds too quickly through the martensitic formation process (I forget the exact numbers on this, but I believe it begins somewhere below 900F.). So the goal is to quench it in oil past the pearlite temperatures (The 1000F), but pull it out from the oil before it reaches the martensite transformation phase. Then it has plenty of time to transform.
If I am wrong about what is happening exactly, and someone wants to school me on this, I'd actually be grateful.
Have you actually tested this? Because I have not only seen a difference in hardness between oil/plate quenching of air hardening steels, but also a hardness difference between plate and air only quench. But I guess it can largely depend on the steel in question, too.
But I also wonder if there are other factors, as well, such as grain size differences. Hardness does not tell the whole story.
And so how will you know you have reached that 1000 F?I am no expert on this, but the way I understand it, is when oil quenching air hardening steels, you not only put a lot of stress on it by doing a full oil quench, but it speeds too quickly through the martensitic formation process (I forget the exact numbers on this, but I believe it begins somewhere below 900F.). So the goal is to quench it in oil past the pearlite temperatures (The 1000F), but pull it out from the oil before it reaches the martensite transformation phase. Then it has plenty of time to transform.
If I am wrong about what is happening exactly, and someone wants to school me on this, I'd actually be grateful.
Have you actually tested this? Because I have not only seen a difference in hardness between oil/plate quenching of air hardening steels, but also a hardness difference between plate and air only quench. But I guess it can largely depend on the steel in question, too.
But I also wonder if there are other factors, as well, such as grain size differences. Hardness does not tell the whole story. I actually planned to do some more extensive testing a year or so ago (I even made a post about it.), but unfortunately due to health reasons I haven't been able to do anything with it until now. It's always been a bit surprising how little information there is on interrupted oil quenching.
Ultimately, I am in no way trying to say it is superior. I just don't trust plate quenching a beveled blade.
And so how will you know you have reached that 1000 F?
You quench until the steel stops glowing - That's within the temperature range you are shooting for. Usually it's about 2-3 seconds for me in my 15s oil.
EDIT: What I personally did, was test on a couple knife blanks of the same size/thickness of what I am working on, timing with a stopwatch in the dark. I also have a thermometer just for my oil, to insure it's at a decently consistent temp when I quench. If you have any doubts about your timing, I'd say you are better interrupting too early than too late. Just toss it between plates and you are there.
I also ALWAYS do a stress relief before heat treating, to eliminate any chances of warping.
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Sorry to double post, but while we're on the subject of oil quenching air hardening steels, I remembered something else that I had read in the past about it.
If I understand correctly, another benefit of a more rapid quench, is that it doesn't allow certain alloys in the steel as much time to "gobble up" carbon and form carbides with it. What I am not certain about, though, is how much this applies to certain steels. Maybe it's true if it has a lot of chromium in it, for example, but not so much if it doesn't. As for how this translates into hardness, I don't really know either, and probably also varies between steels. Hardness doesn't tell the whole story when it comes to real world performance, either.
It's also possible that even if there is a difference, it ultimately is so minor it's not worth considering.
But I am perhaps a little overly obstinate when it comes to this subject. I've had discussions on these forums about this before, and have even had very experienced makers who run heat treat operations tell me that quenching faster makes absolutely no difference and that I have no clue what I am talking about. But in the end, what it comes down to for me, is that Roman Landes recommended quenching 3v in oil, which caries a LOT of weight in my mind.
I can say that I have never once seen a single person do any testing on this (comparing interrupted oil to plate quenching), even people who plate quench thousands of knives for a living and confidently claim that there is no difference. Yet I have seen a difference with 3v, the steel that I have primarily worked with.
If I understand correctly, another benefit of a more rapid quench, is that it doesn't allow certain alloys in the steel as much time to "gobble up" carbon and form carbides with it. What I am not certain about, though, is how much this applies to certain steels. Maybe it's true if it has a lot of chromium in it, for example, but not so much if it doesn't. As for how this translates into hardness, I don't really know either, and probably also varies between steels. Hardness doesn't tell the whole story when it comes to real world performance, either.
It's also possible that even if there is a difference, it ultimately is so minor it's not worth considering.
But I am perhaps a little overly obstinate when it comes to this subject. I've had discussions on these forums about this before, and have even had very experienced makers who run heat treat operations tell me that quenching faster makes absolutely no difference and that I have no clue what I am talking about. But in the end, what it comes down to for me, is that Roman Landes recommended quenching 3v in oil, which caries a LOT of weight in my mind.
I can say that I have never once seen a single person do any testing on this (comparing interrupted oil to plate quenching), even people who plate quench thousands of knives for a living and confidently claim that there is no difference. Yet I have seen a difference with 3v, the steel that I have primarily worked with.
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