Re heat treating 3v

rodriguezryan14

rodriguezryan14

Joined
Jan 6, 2023
Messages
208
Quick question. I have a blade that I heat treated, I’m not to thrilled the way it came out. Kind of an experiment. I’m gonna re heat treat it this weekend. Crucible recommends an an anneal at 1650 for a two hour hold, and slowly cooling in the oven. Is this sufficient? Any other steps? I can’t find anymore information anywhere! Thanks
 
Seedy Lot said:
Wrap in foil.

I am assuming you saw the slow cool is no more then 25F per hour down to 1100f so that is going to be 22 hours of slow cool. You will have to set a target of 1100 F on your oven with ramp of 25F.
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Yup, gotta figure out how to do that. It’s definitely a process. But with the price of a chunk of steel this size, it’s better than scrapping it! What happened, is my oven had messed up while I was heat treating this piece, I blew a fuse on the breaker on a 110 leg. So the oven wouldn’t get up to full temp, it took me a while to figure out what was going on. By that time the blade sat in the oven at around 17-1800 degrees for over 30 minutes. I let it cool off, restarted my oven and put the blade in at 1900 for a 30 minute soak! I got the hardness I was after, but I think I have a lot of retained austenite or something. The edge just acts weird, it’s hard to explain. But it’s not like my usual 3v blades! It’s a 1/4 inch full convex beast of a blade! Definitely not a cheap piece of steel
 
I have a couple 10v knives that my old heat treat guy only hardened to 59 Rc so need to go down the anneal path myself.

When you setup your oven it will be multiple legs for the anneal. Full ramp to 1650F for 2 hour soak then set next leg for 1100F with the 25F ramp and soak time for a couple minutes.
 
Seedy Lot said:
I have a couple 10v knives that my old heat treat guy only hardened to 59 Rc so need to go down the anneal path myself.

When you setup your oven it will be multiple legs for the anneal. Full ramp to 1650F for 2 hour soak then set next leg for 1100F with the 25F ramp and soak time for a couple minutes.
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Sweet. Thanks man. I appreciate it. I don’t ever get many replies here for some odd reason!!
 
I have a thick 3V blade that mostly survived a shop fire, (not mine). Supposing it will need to be annealed before hardening it again?
Also have a plate of 1/8" Hitachi blue that was also in the fire. The plate is fairly warped, but I'm thinking it's salvageable. Wondering where to start with that- should I try and straighten it? Anneal it first? Or what?
 
Lorien said:
I have a thick 3V blade that mostly survived a shop fire, (not mine). Supposing it will need to be annealed before hardening it again?
Also have a plate of 1/8" Hitachi blue that was also in the fire. The plate is fairly warped, but I'm thinking it's salvageable. Wondering where to start with that- should I try and straighten it? Anneal it first? Or what?
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I was originally under the impression that you could just re heat treat some of these high alloy steels. But I’ve been told that it’s better the anneal them before. Granted the annealing process is time consuming. But it’s better than losing that money I guess!
As far as the hitachi blue steel. I’d probably try Larrins det protocol on that one. Makes sense I think.
 
There is a magnet trick that can be useful in these situations. It removes some RA and tempers the blade. Heat it to 120°C, clamp the handle, take two magnets (one each side) and sweep the blade a few times, turn the poles around and repeat. Magnets should attract each other thru steel inducing a magnetic field in it. When the steel is hot, the magnetic field will push the RA to convert to martensite and some carbides will precipitate. Leave it for 3h and check the hardness. It drops at first and hardens while cooling. Sometimes I get +4HRC. But if used too much it will temper to lower hardness.
A thing to consider before reHT.
 
JoeBusic said:
There is a magnet trick that can be useful in these situations. It removes some RA and tempers the blade. Heat it to 120°C, clamp the handle, take two magnets (one each side) and sweep the blade a few times, turn the poles around and repeat. Magnets should attract each other thru steel inducing a magnetic field in it. When the steel is hot, the magnetic field will push the RA to convert to martensite and some carbides will precipitate. Leave it for 3h and check the hardness. It drops at first and hardens while cooling. Sometimes I get +4HRC. But if used too much it will temper to lower hardness.
A thing to consider before reHT.
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Good one. 🤣
 
Larrin said:
Good one. 🤣
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Out of curiosity, what would a high temper do? Considering the heat treat was already done. And it was tempered at 400. If I have some ra left, will a higher temper take care of it? It may be easier to try that, than to anneal and re heat treat the blade! I’m not worried about the fine edge stability on this particular blade! It’s mainly be used for skinning and butchering large game!
 
rodriguezryan14 said:
Out of curiosity, what would a high temper do? Considering the heat treat was already done. And it was tempered at 400. If I have some ra left, will a higher temper take care of it? It may be easier to try that, than to anneal and re heat treat the blade! I’m not worried about the fine edge stability on this particular blade! It’s mainly be used for skinning and butchering large game!
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Higher temperature tempering can reduce or eliminate RA but it depends on how much retained austenite, how stable it is, and what tempering temperature is chosen. Sometimes relatively high tempering temperatures are necessary in combination with 3-4 tempers. In this case it also depends on whether you are right that RA is the problem with your heat treatment.
 
Larrin said:
Higher temperature tempering can reduce or eliminate RA but it depends on how much retained austenite, how stable it is, and what tempering temperature is chosen. Sometimes relatively high tempering temperatures are necessary in combination with 3-4 tempers. In this case it also depends on whether you are right that RA is the problem with your heat treatment.
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This is currently a best guess scenario! Lol. I only know that this blade is acting much different than any of the blades I’ve made in the past! I think it took a little too long to get it into cryo too. So I’m guessing it’s a retained austenite issue!
 
So an update for anyone that’s interested! I ended up grinding off my handles this past weekend and re tempered this 3v blade at 1000 degreesx2 for 2 hours each. This seemed to resolve the little issue I was having. Now I’m sure it was retained austenite. And apparently it was too much. I was distracted by my son when I was heat treating this blade originally, and I think it took me too long from quench to cryo! Easy enough fix. I did put it through a nice assortment of heavy testing over the weekend. And surprisingly the edge held up extremely well. Even chopping into antler and oak. I had absolutely no edge dulling or rolling, and final rc was right around 59. The design of this knife is a heavier wilderness hunter, full convex and about .020 behind the edge! It’s a batonning and skinning beast of a blade! And whoever says it’s to thick for skinning, trust me, I have plenty of time working many elk in the field with the same geometry! And I’ve never had an issue!! A good convex grind and a sharp edge will rip right through heavy elk hide no problem!! Just thought I would share
 
rodriguezryan14 said:
So an update for anyone that’s interested! I ended up grinding off my handles this past weekend and re tempered this 3v blade at 1000 degreesx2 for 2 hours each. This seemed to resolve the little issue I was having. Now I’m sure it was retained austenite. And apparently it was too much. I was distracted by my son when I was heat treating this blade originally, and I think it took me too long from quench to cryo! Easy enough fix. I did put it through a nice assortment of heavy testing over the weekend. And surprisingly the edge held up extremely well. Even chopping into antler and oak. I had absolutely no edge dulling or rolling, and final rc was right around 59. The design of this knife is a heavier wilderness hunter, full convex and about .020 behind the edge! It’s a batonning and skinning beast of a blade! And whoever says it’s to thick for skinning, trust me, I have plenty of time working many elk in the field with the same geometry! And I’ve never had an issue!! A good convex grind and a sharp edge will rip right through heavy elk hide no problem!! Just thought I would share
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no photo no fish :) Let see that knife !
 
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