What can you tell me about tempering with 24 hr. cycles between heats? Is there any real advantage to doing so with file steel, 1095 steel, or 01, and just what is happening with the steel, if so? If this proceedure is advantageous, how much better than three one hour heats, with a room temp cool down in between?
-
The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
Mete, or Kevin Cashen
- Thread starter LRB
- Start date
Alan Molstad
Banned
- Joined
- Aug 13, 2006
- Messages
- 422
I have been reading about this topic, and so far I have yet to find any scientific backing for the use of more than one good quench.
However the benefits of a person doing more than one quench seem strong by the way the testimonials come forth from the people that use it on their knives.
If nothing else, the use of 2 or 3 or more quenches on a blade is good practice.
For many new bladesmiths such as myself, the moment when to quench is a pure judgment call, hopefully based on good past experience.
But I do understand why a Japanese swordsmith would always offer prayers before a heat-treatment, there is always a large amount of 'unknowns" to a quench, and a bit of luck or Divine intervention is handy.
Perhaps doing 3 quenches on a knife works so well for some people simply because it's a great way to practice and get it right.
However the benefits of a person doing more than one quench seem strong by the way the testimonials come forth from the people that use it on their knives.
If nothing else, the use of 2 or 3 or more quenches on a blade is good practice.
For many new bladesmiths such as myself, the moment when to quench is a pure judgment call, hopefully based on good past experience.
But I do understand why a Japanese swordsmith would always offer prayers before a heat-treatment, there is always a large amount of 'unknowns" to a quench, and a bit of luck or Divine intervention is handy.
Perhaps doing 3 quenches on a knife works so well for some people simply because it's a great way to practice and get it right.
I appreciate the input, but my concern is with the temper process. I do only one quench as far as the hardening. When using a temperature controled oven, there is little question as to when to quench. It is more a matter of knowing the recommended soak time for a given steel, the recommended temperature at which to soak it, and then properly carrying through with it. Occasionaly, I read, and hear reference to doing three tempers, with a 24 hr. interval between the heats, and would like the opinion of those who know much more than I.
Phillip Patton
Knifemaker / Craftsman / Service Provider
- Joined
- Jul 25, 2005
- Messages
- 5,362
When you say heats, are you talking about hardening, or tempering?
Phillip Patton
Knifemaker / Craftsman / Service Provider
- Joined
- Jul 25, 2005
- Messages
- 5,362
Oops, our posts crossed. 
I won't speak for mete or Kevin, (though I think I know what they would say)
but I don't think there's any benefit to waiting 24 hours in between. Also, with the simpler steels, 2 tempers is usually enough. When you get into high speed steels, 3 or more tempers is recommended.
I won't speak for mete or Kevin, (though I think I know what they would say)
but I don't think there's any benefit to waiting 24 hours in between. Also, with the simpler steels, 2 tempers is usually enough. When you get into high speed steels, 3 or more tempers is recommended.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
- Messages
- 38,381
Alan - He is talking about temper cycles,not quench cycles.
LRB - A lot happens while steel is "just sitting there at room temperature".After the quench the austenite is converted into martensite, but there is still some austenite floating around that hasn't changed yet. This change into martensite starts at the Ms point (about 400F for 1095) and continues until the Mf point (which can be around -100F) if given the chance (Ed Fowlers overnight in the freezer).Most is converted by the time it gets to room temperature.In between the Ms and Mf points the metal is a mixture of martensite and unconverted austenite.The change does not happen as rapidly as quenching would make you think.When the steel has cooled to room temperature and then is re-heated to tempering point the remaining austenite is again in the Mf to Ms range and can convert to martensite when the steel is cooled down again.This added martensite will be untempered martensite.That is why you need another temper cycle. A rest of about 24 hours between the first temper and the second allows enough time for conversion.The process actually continues for weeks,but the bulk happens in 24 hours.It seems that three cycles gains as much martensite as is reasonable to expect.If you cool the steel to below -105F (cryo treatment) during these rest periods,you will get all that you can out of it.This is greatly advantageous for the more complex structures in stainless steels,but gains very little in simple steels like 1095.
mete will give a better explanation,but this is my take on what is happening in the steel.
Stacy
LRB - A lot happens while steel is "just sitting there at room temperature".After the quench the austenite is converted into martensite, but there is still some austenite floating around that hasn't changed yet. This change into martensite starts at the Ms point (about 400F for 1095) and continues until the Mf point (which can be around -100F) if given the chance (Ed Fowlers overnight in the freezer).Most is converted by the time it gets to room temperature.In between the Ms and Mf points the metal is a mixture of martensite and unconverted austenite.The change does not happen as rapidly as quenching would make you think.When the steel has cooled to room temperature and then is re-heated to tempering point the remaining austenite is again in the Mf to Ms range and can convert to martensite when the steel is cooled down again.This added martensite will be untempered martensite.That is why you need another temper cycle. A rest of about 24 hours between the first temper and the second allows enough time for conversion.The process actually continues for weeks,but the bulk happens in 24 hours.It seems that three cycles gains as much martensite as is reasonable to expect.If you cool the steel to below -105F (cryo treatment) during these rest periods,you will get all that you can out of it.This is greatly advantageous for the more complex structures in stainless steels,but gains very little in simple steels like 1095.
mete will give a better explanation,but this is my take on what is happening in the steel.
Stacy
Alan Molstad
Banned
- Joined
- Aug 13, 2006
- Messages
- 422
That is also a question I ask too, I have read about knife makers who allow a quenched blade to fully cool in the oil before tempering, and I have learned of others who say I should have my tempering oven all ready warmed up before I heat-treat so as to be able to quench and temper bam-bam...
What are your views?
What are your views?
- Joined
- Jun 10, 2003
- Messages
- 15,288
The questions are a bit confusing. When you quench the stresses in the martensite are very high . The steel should be tempered immediately after quenching to prevent those stresses from cracking the steel .Most of the tempering is complete in two hours .The higher carbon and alloy steels may gain from a second two hour temper. Again the point is to temper immediately , no gain and some danger will result by waiting 24 hours for the first or second temper.
- Joined
- Jul 21, 2001
- Messages
- 2,869
I know I was not invited, but can not help myself.
I speak only about 5160 and 52100 steel.
If a blade breaks after hardening, you have either overheated, forged improperly, some very radical blade design or poor quality steel. Trying to save an illconceived blade by tempering immediately is only doing a diservice to someone who may need it in the future.
I have not had a blade crack between hardening and tempering for over 30 years. (experimental blades excepted)
I speak only about 5160 and 52100 steel.
If a blade breaks after hardening, you have either overheated, forged improperly, some very radical blade design or poor quality steel. Trying to save an illconceived blade by tempering immediately is only doing a diservice to someone who may need it in the future.
I have not had a blade crack between hardening and tempering for over 30 years. (experimental blades excepted)
Mr. Fowler, I welcome any input you may wish to offer, or anyone else with good knowledge of steel. My intent was not to exclude anyone, but to get the attention of those I know and trust to have great knowledge on the subject. Many thanks to all who have replied.
- Joined
- Jan 5, 2005
- Messages
- 2,531
Ed Fowler said:
I don't think anyone would gripe if you showed up "uninvited" to anything Mr. Fowler
Especially when it is Blade related 
Alan Molstad
Banned
- Joined
- Aug 13, 2006
- Messages
- 422
Is the use of a set time of "24 hours" between tempering just something that is a nice round number?
But is it not actually based on true science?
I have been reading about some knife makers who always take 24 hours between doing a 2nd quenching or a 2nd tempering. But the way people talk about this it just seems to me that the number "24" is just like a nice round number.
More or less like saying "The next day".
Are we meaning that 23 hours between tempering is wrong?
22 hours is too soon?
and 25 hours is a little late?
I have a book on how Japanese swordsmiths heat-treat their swords out of the water-quench. They take it right out of the quench water back to the hot coals for a few seconds , then quench again. They may even repeat this once more, and thats all the tempering they use.
But is it not actually based on true science?
I have been reading about some knife makers who always take 24 hours between doing a 2nd quenching or a 2nd tempering. But the way people talk about this it just seems to me that the number "24" is just like a nice round number.
More or less like saying "The next day".
Are we meaning that 23 hours between tempering is wrong?
22 hours is too soon?
and 25 hours is a little late?
I have a book on how Japanese swordsmiths heat-treat their swords out of the water-quench. They take it right out of the quench water back to the hot coals for a few seconds , then quench again. They may even repeat this once more, and thats all the tempering they use.
- Joined
- Jul 21, 2001
- Messages
- 2,869
Thank you gentlemen:
Another source of failure between hardening and termpering can be the guenchent you are using, can be too fast for the steel.
One aspect that may be significant is to note where it cracks when the quenchant is not in tune with your steel.
For example: if a guench is too fast and results in many cracks evenly dispersed throughout the blade your work previous to forging may have been well concieved and executed. If it only cracks in one place, you may have concentrated stress in that area through design or thermal application or forging practice.
When ever I read that a bladesmith has a blade crack using 5160 or 52100 because he did not temper immediately, I figure he either had some other steel, poor quality steel or poor forging practice including control of thermal variables.
It takes time and practice but when you come to understand your steel you learn to nurture steel into a knife. Nothing happens fast, some events take months and more. We are only beginning to understand these variables, some can only be observed and their nature implied.
A great book if you can find one is "The Prevention of Metals Under Repeated Stress" by the staff of the Battelle Memorial Institute. Your lybrary may be able to get one on loan for your enjoyment. After your third reading you will have many more questions and a lot of understanding. It was written for the Bureau of Aeronatics of the Navy Department in 1940. It will lead you to more research and will provide good times if you are so inclined.
Another source of failure between hardening and termpering can be the guenchent you are using, can be too fast for the steel.
One aspect that may be significant is to note where it cracks when the quenchant is not in tune with your steel.
For example: if a guench is too fast and results in many cracks evenly dispersed throughout the blade your work previous to forging may have been well concieved and executed. If it only cracks in one place, you may have concentrated stress in that area through design or thermal application or forging practice.
When ever I read that a bladesmith has a blade crack using 5160 or 52100 because he did not temper immediately, I figure he either had some other steel, poor quality steel or poor forging practice including control of thermal variables.
It takes time and practice but when you come to understand your steel you learn to nurture steel into a knife. Nothing happens fast, some events take months and more. We are only beginning to understand these variables, some can only be observed and their nature implied.
A great book if you can find one is "The Prevention of Metals Under Repeated Stress" by the staff of the Battelle Memorial Institute. Your lybrary may be able to get one on loan for your enjoyment. After your third reading you will have many more questions and a lot of understanding. It was written for the Bureau of Aeronatics of the Navy Department in 1940. It will lead you to more research and will provide good times if you are so inclined.
- Joined
- Jul 21, 2001
- Messages
- 2,869
Alan: your thoughts came in while I was writing the above post.
Next day is ike you said a practical temporal cycle. The way Rex explained it to me, Stuff keep happening always, you bet 90 % the fitst cycle, 90 % of the remaining 10 % the second cycle and 90% of what was left after the second cycle on the third. The time between is just to get as much as you can. I have left blades in the freezer for months, as a matter of fact, that is where I store blades after heat treat until I am ready to work on them again.
Each is dated so I know. When you finish the blade and test you can reffer back to what you have recorded and possibly gain a little more insight.
When you read how some other smiths did it, read for understanding of variables and realize how they may only apply to their steel and time, but know that these variables may have application to what you are doing now.
And enjoy the trip.
Next day is ike you said a practical temporal cycle. The way Rex explained it to me, Stuff keep happening always, you bet 90 % the fitst cycle, 90 % of the remaining 10 % the second cycle and 90% of what was left after the second cycle on the third. The time between is just to get as much as you can. I have left blades in the freezer for months, as a matter of fact, that is where I store blades after heat treat until I am ready to work on them again.
Each is dated so I know. When you finish the blade and test you can reffer back to what you have recorded and possibly gain a little more insight.
When you read how some other smiths did it, read for understanding of variables and realize how they may only apply to their steel and time, but know that these variables may have application to what you are doing now.
And enjoy the trip.
- Joined
- Jun 25, 2001
- Messages
- 8,474
I add just a quick one..
RLB file steel? are you stock grinding or forging??
I have not cracked a blade in 32 years..of which 24 were with high carbon steel only.. I've left quenched blades so long I've forgotten if I tempered them or not
.. so I'd temper them anyway again if for only not knowing..
this is not to say if you do not temper ASAP you would not have a blade or two crack on you..I'll call it luck on my part..know your steel and the heats..
with the SS I do snap temper and Cryo ASAP. then temper them again, the 2nd temper I don't worry about the time that goes by .it's just the way I do the SS..I've only been at the SS for about 8 years now..
it's been said many times and I believe it very true.. if your nail your H/T correctly you'll have less problems later in every aspect.. I will say , I'm mostly a stock grinder in comparison to my forging
my stock grind forged steel comes from the steel foundry where as all steel is forged to start with..
and I would guess most of the time will not be forged incorrectly after all this is where steel comes from these days .
too, I will back ED up ( not that I need to
) in saying, you can mess up perfectly good steel by forging it if you don't know what you are doing..
RLB file steel? are you stock grinding or forging??
I have not cracked a blade in 32 years..of which 24 were with high carbon steel only.. I've left quenched blades so long I've forgotten if I tempered them or not
.. so I'd temper them anyway again if for only not knowing.. this is not to say if you do not temper ASAP you would not have a blade or two crack on you..I'll call it luck on my part..know your steel and the heats..
with the SS I do snap temper and Cryo ASAP. then temper them again, the 2nd temper I don't worry about the time that goes by .it's just the way I do the SS..I've only been at the SS for about 8 years now..
it's been said many times and I believe it very true.. if your nail your H/T correctly you'll have less problems later in every aspect.. I will say , I'm mostly a stock grinder in comparison to my forging
my stock grind forged steel comes from the steel foundry where as all steel is forged to start with..
and I would guess most of the time will not be forged incorrectly after all this is where steel comes from these days .
too, I will back ED up ( not that I need to
) in saying, you can mess up perfectly good steel by forging it if you don't know what you are doing..- Joined
- Dec 22, 2005
- Messages
- 27
Ed Fowler said:
Ed, can you explain a little how these pockets of high stress could hurt the knife later? If a stress field was created due to uneven cross section or cooling sresses, uneven structure change, etc.. it would make a bad knife if the knife was not tempered to a homogeneous state later on. Point is, doesn't tempering at the end get rid of these residual stresses?
- Joined
- Jul 21, 2001
- Messages
- 2,869
Dan: Thanks for the vote of conficence.
Twistedneck: At one time I may have figured all stresses would be cleaned up with future thermal cycles. After studying the fatigue failure books that I am reading now, I would not take a chance. One of my greatest fears is that one day a man's life might depend on one of my knives and it fails. This has been a driving force in our work. Anyone who has ever had a knife fail when it was needed will know what I am talking about.
Twistedneck: At one time I may have figured all stresses would be cleaned up with future thermal cycles. After studying the fatigue failure books that I am reading now, I would not take a chance. One of my greatest fears is that one day a man's life might depend on one of my knives and it fails. This has been a driving force in our work. Anyone who has ever had a knife fail when it was needed will know what I am talking about.
- Joined
- Jul 4, 2005
- Messages
- 135
A knife that has only one third of its blade hardened (edge quench) may have less stress than one which has been fully quenched....and maybe a snap temper cycle is not so critical?
Alternatively, a knife which has not been hardened to its full potential may have less stress than one where the transformation had been more efficient (ie too slow a quench or inacurate temperature at quenching)
Just a thought.
I dont see why giving a snap temper immediately after hardening will effect any future transformation changes that are going to occur much later ....Can someone explain why a one off snap temper immediately after hardening will stop anything from happening that is going to happen anyway...?
Thanks.
Alternatively, a knife which has not been hardened to its full potential may have less stress than one where the transformation had been more efficient (ie too slow a quench or inacurate temperature at quenching)
Just a thought.
I dont see why giving a snap temper immediately after hardening will effect any future transformation changes that are going to occur much later ....Can someone explain why a one off snap temper immediately after hardening will stop anything from happening that is going to happen anyway...?
Thanks.
- Joined
- Sep 9, 2003
- Messages
- 2,361
Oh boy! I just got off the road from the ABS Mid American Hammer-In, I am tired, cranky and my acid reflux is killing me, after reading some of the information in this thread I would rather have a tooth pulled than deal with some of it right now, but I was called upon for input so...
Kevin, I think your feelings are serving you correctly, the snap temper is good for relieving some of the BCT condition that a proper quench should have produced enough of to worry about. Higher tempering temperatures will begin to actually precipitate carbides (although incredibly small). That would be the difference, the idea being that one would want to save the retained austenite for complete conversion to martensite instead of possibly transforming other precipitates in a full temper.
If one has nothing to fear from going without a temper, they didn't get the dang thing fully hardened to begin with!
Get the thing fully hard, temper it as soon as you get as close to Mf as possible and without delay. After the first temper relax a little bit more yourself, but get onto the second when you can. If something as simple as 1095 is giving one that much retained austenite grief, they need to fix their heat treatment- somethings really wrong. If an alloy is a little richer, that is all the more reason not screw around and encourage retained austenite, so once again- fix your heat treatment! If you can't get the martensite you need in the quench- fix your #$$% heat treatment!
I am more than happy to give this input to you LRB, but you don't need me you can also ask the other 99% of the world that has been suscessfully heat treating steel for the last 100 years, but then I guess that is what mete has helped confirm as well.
Sorry I should just go to bed now:grumpy:
Kevin, I think your feelings are serving you correctly, the snap temper is good for relieving some of the BCT condition that a proper quench should have produced enough of to worry about. Higher tempering temperatures will begin to actually precipitate carbides (although incredibly small). That would be the difference, the idea being that one would want to save the retained austenite for complete conversion to martensite instead of possibly transforming other precipitates in a full temper.
If one has nothing to fear from going without a temper, they didn't get the dang thing fully hardened to begin with!
Get the thing fully hard, temper it as soon as you get as close to Mf as possible and without delay. After the first temper relax a little bit more yourself, but get onto the second when you can. If something as simple as 1095 is giving one that much retained austenite grief, they need to fix their heat treatment- somethings really wrong. If an alloy is a little richer, that is all the more reason not screw around and encourage retained austenite, so once again- fix your heat treatment! If you can't get the martensite you need in the quench- fix your #$$% heat treatment!
I am more than happy to give this input to you LRB, but you don't need me you can also ask the other 99% of the world that has been suscessfully heat treating steel for the last 100 years, but then I guess that is what mete has helped confirm as well.
Sorry I should just go to bed now:grumpy: