I sorry for last evening on the RC machine. It right on the mark so I wrapped a blade in 309 ss like yesterday heated it up to 1500 degrees soaked for 10 mins., took it out and got it out of the ss wrap and cooled it in fluid. I gave it a test 34 RC. I'm sure it took a min. to unwrap before I could cool. do you think that is why it only read 34RC. Thinking that I reheated to 1500 and soaked for 10 mins. without wrapping and immediately cooled in fluid. The RC reading came up to 54 which isn't high enough. I would like 58 or 59RC. I did have to sand the blade after hardening because of scale (no wrap). Do you think Canola oil will bring it up? If so how much should I get? Hope you still can help me out. Thanks
hang with me guys on tempering
- Thread starter Groucho
- Start date
EdCaffreyMS
"The Montana Bladesmith"
A couple of things that come to mind....
1. I'm pretty sure that taking the time to unwrap, then quench caused a lack of hardening. What a lot of folks don't realize is that the recommended "austinizing" temps for steels means that the steel needs to be AT THAT TEMP WHEN IT HITS THE QUENCH.
Generally speaking, in order for a carbon/plain steel blade to fully harden, it must go from its austinizing temp, to 400F or less, in 6 seconds or less.
I once visited with a fella on the phone for over an hour, trying to help him with steel that "wouldn't harden".....I finally asked him to take me step by step through his procedure....when he got to "I take it out of the forge and WALK to the quench tank..." (RED FLAG) I asked him where his quench tank was in relationship to his forge..... "about 15 feet away" was the response. He said he was heating to 1550F, then taking the blade(s) out of the forge and to the quench tank. I'm sure his blades dropped below austinizing temp in that distance. Again... the steel must be at its austinizing temp WHEN IT HITS THE QUNECH MEDIA. We solved his whole issue by him moving the quench tank next to his forge....where all he had to do was remove the blade from the forge, and simply turn 90 degrees to get it in the quench.
2. Personally I think the temp you're using it a bit too low. Nearly all of the damscus I produce is 1084/15N20, and I always take it to 1550F for the quench, then temper 3X for 2 hrs each at 415F. Everything we do in knifemaking has a level of "give-n-take" to it.....in this case I go slightly above the austinizing temps of SOME carbon steels. I risked some slight grain growth by doing so, but in return I ensure a blade is at its austinizing temp when it hits the quench.
3. Soaking: Although you hear about it a great deal these days in many "knife" circles, I totally disagree with soaking any carbon steel at or beyond its austinizing temp. With plain carbon steels, any temp in excess of the austinizing temp causes grain growth at a expodential rate. Many people use this "trade off" to achieve Rc numbers that they feel are impressive, when in reality it causes more harm then good through increased grain size, which manifests itself in a number of different way in the finished blade...... this could be displayed in difficulty sharpening, a lack of edge retention,the edge being "chippy" in a fine cross section, and/or a more fragile blade then one would achieve without the soaking.
OK, all that being said, there will come a time when you simply run out of "chances" when it comes to hardening/heat treating. If you get to a point where you keep seeing lower and lower Rc numbers, its a good bet that you've reached the limit and its time to start on a new blade. Personally, the limit I've set myself is twice......it I don't get it in two tries, I start over.
Finally, don't let yourself get hung up on Rc numbers. While they are a "feel good" sorta thing, and they can provide valuable insight to a knifemaker. they are something to be "used" rather then "highly sought". To put it in perspective, I've seen many well designed/executed blades over the years that only went Rc 54-58, that would far out perform poorly designed and executed blades with Rc hardness levels in the lower 60s.
The best thing to do is use the situations you've encountered as learning tools. When you come to a result that is less then what you anticipated/expected, walk backwards through the process you used and try to pinpoint possible causes of you not achieving what you expected/anticipated, then evaluate each of those steps and determine what you could or should do differently to achieve your desired outcome, that is one of the things that most long term knifemakers share.....learning to evaluate and correct possible "flaws" in thier procedures, and understanding that we are all in a constant state of learning.
Keep us posted!
1. I'm pretty sure that taking the time to unwrap, then quench caused a lack of hardening. What a lot of folks don't realize is that the recommended "austinizing" temps for steels means that the steel needs to be AT THAT TEMP WHEN IT HITS THE QUENCH.
Generally speaking, in order for a carbon/plain steel blade to fully harden, it must go from its austinizing temp, to 400F or less, in 6 seconds or less.
I once visited with a fella on the phone for over an hour, trying to help him with steel that "wouldn't harden".....I finally asked him to take me step by step through his procedure....when he got to "I take it out of the forge and WALK to the quench tank..." (RED FLAG) I asked him where his quench tank was in relationship to his forge..... "about 15 feet away" was the response. He said he was heating to 1550F, then taking the blade(s) out of the forge and to the quench tank. I'm sure his blades dropped below austinizing temp in that distance. Again... the steel must be at its austinizing temp WHEN IT HITS THE QUNECH MEDIA. We solved his whole issue by him moving the quench tank next to his forge....where all he had to do was remove the blade from the forge, and simply turn 90 degrees to get it in the quench.
2. Personally I think the temp you're using it a bit too low. Nearly all of the damscus I produce is 1084/15N20, and I always take it to 1550F for the quench, then temper 3X for 2 hrs each at 415F. Everything we do in knifemaking has a level of "give-n-take" to it.....in this case I go slightly above the austinizing temps of SOME carbon steels. I risked some slight grain growth by doing so, but in return I ensure a blade is at its austinizing temp when it hits the quench.
3. Soaking: Although you hear about it a great deal these days in many "knife" circles, I totally disagree with soaking any carbon steel at or beyond its austinizing temp. With plain carbon steels, any temp in excess of the austinizing temp causes grain growth at a expodential rate. Many people use this "trade off" to achieve Rc numbers that they feel are impressive, when in reality it causes more harm then good through increased grain size, which manifests itself in a number of different way in the finished blade...... this could be displayed in difficulty sharpening, a lack of edge retention,the edge being "chippy" in a fine cross section, and/or a more fragile blade then one would achieve without the soaking.
OK, all that being said, there will come a time when you simply run out of "chances" when it comes to hardening/heat treating. If you get to a point where you keep seeing lower and lower Rc numbers, its a good bet that you've reached the limit and its time to start on a new blade. Personally, the limit I've set myself is twice......it I don't get it in two tries, I start over.
Finally, don't let yourself get hung up on Rc numbers. While they are a "feel good" sorta thing, and they can provide valuable insight to a knifemaker. they are something to be "used" rather then "highly sought". To put it in perspective, I've seen many well designed/executed blades over the years that only went Rc 54-58, that would far out perform poorly designed and executed blades with Rc hardness levels in the lower 60s.
The best thing to do is use the situations you've encountered as learning tools. When you come to a result that is less then what you anticipated/expected, walk backwards through the process you used and try to pinpoint possible causes of you not achieving what you expected/anticipated, then evaluate each of those steps and determine what you could or should do differently to achieve your desired outcome, that is one of the things that most long term knifemakers share.....learning to evaluate and correct possible "flaws" in thier procedures, and understanding that we are all in a constant state of learning.
Keep us posted!
so Ed you do not wrap your blades and just deal with the scale. I am really learning from this thread. It does seem that every time I enter the shop I learn something. I'll keep you informed on the project. I hope this forum stays around awhile, I'll need it.
I walked 20ft. To quench outside. I'll move it close. Should I get canola oil to quench instead of hydraulic fluid. How much do I need for it to be adequate for quench?
Thanks all.
I walked 20ft. To quench outside. I'll move it close. Should I get canola oil to quench instead of hydraulic fluid. How much do I need for it to be adequate for quench?
Thanks all.
EdCaffreyMS
"The Montana Bladesmith"
Oh yeah! If you have to go 20ft to get to the quench tank, you're WAY below the temp you need to be at when quenching. 
Move the quench tank where its within arm's reach of the heat source you're using!
For years I used Vet. grade mineral oil for a quenchant.... it got me through my JS and MS. Currently I have both Parks 50 and Mineral oil quench tanks in the shop. Canoloa, peanut, vegtable oils.....all will work. The key is to ensure you pre-heat those types of oils. Common thinking is that the colder a quench is, the faster it works....just the opposite is true. If you introduce a 1550F piece of steel into any of those oils at room temp, the oil immedately surrounding the steel flash boils, and creates a vapor pocket that holds the heat close to the blade. Pre-heating thins the oil's viscosity, and can prevent that vapor pocket from forming.....meaning that when specific oils are heated, they actually cool steel more rapidly. Personally, I feel that 2 gallons is the minimum for quenching, but that can vary based on the size and number of blades a person quenches. The key with they commonly used "household" quenchants is the pre-heat..... 120-130F is the target I generally recommend (use a candy or meat thermometer). The "trick" when it comes to using pre-heated oil is that IF the oil temp reaches or exceeds 180F, it will not cool rapidly enough to ensure full hardening. Thats why I recommend at least 2 gallons.....anything less will get beyond 180F temp if you quench 1-2 small hunters.
Move the quench tank where its within arm's reach of the heat source you're using! For years I used Vet. grade mineral oil for a quenchant.... it got me through my JS and MS. Currently I have both Parks 50 and Mineral oil quench tanks in the shop. Canoloa, peanut, vegtable oils.....all will work. The key is to ensure you pre-heat those types of oils. Common thinking is that the colder a quench is, the faster it works....just the opposite is true. If you introduce a 1550F piece of steel into any of those oils at room temp, the oil immedately surrounding the steel flash boils, and creates a vapor pocket that holds the heat close to the blade. Pre-heating thins the oil's viscosity, and can prevent that vapor pocket from forming.....meaning that when specific oils are heated, they actually cool steel more rapidly. Personally, I feel that 2 gallons is the minimum for quenching, but that can vary based on the size and number of blades a person quenches. The key with they commonly used "household" quenchants is the pre-heat..... 120-130F is the target I generally recommend (use a candy or meat thermometer). The "trick" when it comes to using pre-heated oil is that IF the oil temp reaches or exceeds 180F, it will not cool rapidly enough to ensure full hardening. Thats why I recommend at least 2 gallons.....anything less will get beyond 180F temp if you quench 1-2 small hunters.
Kayakersteve
Well-Known Member
Just heat a piece of bar or stock and place in tank prior to doing quench - I usually have to do this 3 x to bring my oil up to 120
EdCaffreyMS
"The Montana Bladesmith"
Yep! A heated piece of barstock works great. Many times this will take the oil temp beyond what you want, but that's OK....just keep an eye on it, and try to time your quench when the temp is on the fall.
Years ago I built a quench tank that has "wells" in each end, with 120v hot water heater elements....hooked into a PID....all I have to do is flip a toggle switch, and the tank goes to 125F.
Years ago I built a quench tank that has "wells" in each end, with 120v hot water heater elements....hooked into a PID....all I have to do is flip a toggle switch, and the tank goes to 125F.
samuraistuart
Well-Known Member
My understanding of quench and timing is different than Ed's. But to be sure, Ed is right over the target here. 20 feet away is about 18 or 19 feet too far, and a LOT of heat will dissipate walking that distance no doubt about it!
This is how I understand quench and timing:
Let's use as an example 1095 steel, which has a pearlite nose of less than one second. This means that the OIL has less than one second to go from austenite down to under 900F. To be sure, it takes at least ONE second to move the blade from the heat source to the quench tank, and then add on top of that the time it takes the oil to go from austenite to under 900F. I would dare say it would then be impossible to beat the pearlite nose of 1095 if we had less than once second to go from 1500F inside our kiln/oven/forge down to under 900F. What this then means is that there is a time frame between removing the blade from the heat to the oil that really has nothing to do with the "pearlite nose". That is to say.......if you heat the blade up to 1500F, whatever you put into solution at 1500F will still be in solution until the steel cools down to it's Ar1 temp or whatever its called, somewhere around 1300F or 1350F. So as long as the steel is still austenite (has not gone thru it's phase change upon cooling) when you reach the quench tank....you are still good to go.
So our 1095 example....we have our blade heated to 1500F and it has soaked for 10 minutes and now we need to quench it. Remember, the 1095 has less than ONE second to cool from austenite to 900F. So we remove our blade from the heat, quickly but smoothly and safely we transfer it to our quench oil, which probably will take 2 seconds, and into the oil it goes. Then the quench oil has a job to do ..... in less than ONE second!
I hope that makes sense. It's not like you have a total of less than one second to go from 1500 to under 900F. The oil has less than ONE second to go from austenite to less than 900F. And as long as it is still austenite when you place the blade in the oil, whatever you put into solution at whatever heat you chose will STILL be in solution as long as it is still austenite and not undergone it's phase change upon cooling.
And to extrapolate to 52100....the "pearlite nose" there is around 3 seconds. It would be the job of the quench medium to go from austenite to under 900F in three seconds.
1084 has a "pearlite nose" of less than one second as well. I was not aware of that...thinking it had a longer PN, but I was mistaken. It is indeed less than one second....about .75 seconds....very similiar to 1095.
I myself would stick closer to 1500F with 1084 and 15n20. 1550F is about 50° too hot in my book for 1084 or 15n20. Just different opinion on target temp...that's all. Ed is an encyclopedia of knowledge.
This is how I understand quench and timing:
Let's use as an example 1095 steel, which has a pearlite nose of less than one second. This means that the OIL has less than one second to go from austenite down to under 900F. To be sure, it takes at least ONE second to move the blade from the heat source to the quench tank, and then add on top of that the time it takes the oil to go from austenite to under 900F. I would dare say it would then be impossible to beat the pearlite nose of 1095 if we had less than once second to go from 1500F inside our kiln/oven/forge down to under 900F. What this then means is that there is a time frame between removing the blade from the heat to the oil that really has nothing to do with the "pearlite nose". That is to say.......if you heat the blade up to 1500F, whatever you put into solution at 1500F will still be in solution until the steel cools down to it's Ar1 temp or whatever its called, somewhere around 1300F or 1350F. So as long as the steel is still austenite (has not gone thru it's phase change upon cooling) when you reach the quench tank....you are still good to go.
So our 1095 example....we have our blade heated to 1500F and it has soaked for 10 minutes and now we need to quench it. Remember, the 1095 has less than ONE second to cool from austenite to 900F. So we remove our blade from the heat, quickly but smoothly and safely we transfer it to our quench oil, which probably will take 2 seconds, and into the oil it goes. Then the quench oil has a job to do ..... in less than ONE second!
I hope that makes sense. It's not like you have a total of less than one second to go from 1500 to under 900F. The oil has less than ONE second to go from austenite to less than 900F. And as long as it is still austenite when you place the blade in the oil, whatever you put into solution at whatever heat you chose will STILL be in solution as long as it is still austenite and not undergone it's phase change upon cooling.
And to extrapolate to 52100....the "pearlite nose" there is around 3 seconds. It would be the job of the quench medium to go from austenite to under 900F in three seconds.
1084 has a "pearlite nose" of less than one second as well. I was not aware of that...thinking it had a longer PN, but I was mistaken. It is indeed less than one second....about .75 seconds....very similiar to 1095.
I myself would stick closer to 1500F with 1084 and 15n20. 1550F is about 50° too hot in my book for 1084 or 15n20. Just different opinion on target temp...that's all. Ed is an encyclopedia of knowledge.
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EdCaffreyMS
"The Montana Bladesmith"
To me, scale is just a by product (something that happens) during heat treat. If the atmosphere is correct inside the heat source you're using (forge, oven, etc) then scale is minimal. This is one of the reasons I dislike a heat treat oven for carbon/plain steels..... IF you choose to soak in a heat treat oven, the amount of scale is generally huge, and can be a real problem. Several fellow knifemakers have solved the issue by injecting nitrogen or argon into their heat treat ovens......in that case the blades come out nearly scale free. The way I adapted to the issue is leaving blades oversized prior to heat treat. Doing so gives me some "wiggle room" to clean up scale (and/or any minor warping) during finish grinding.
I get the impression that you might be finishing your blade(s) a bit too much prior to heat treat? Its common for makers using stainless steels to go very close to finished dimensions prior to heat treat, but doing that with carbon/plain steels creates often creates more problems then it solves. Its not uncommon for me to leave edges 3/32-1/8" thick prior to heat treating.
I get the impression that you might be finishing your blade(s) a bit too much prior to heat treat? Its common for makers using stainless steels to go very close to finished dimensions prior to heat treat, but doing that with carbon/plain steels creates often creates more problems then it solves. Its not uncommon for me to leave edges 3/32-1/8" thick prior to heat treating.
Self Made Knives
Well-Known Member
First, you should listen to the pros and their advice for sure. But, I like to finish my carbon steel blades to near finished dimensions on everything but the bevels. I do leave some meat on there, but everything else is pretty much where I want it when I heat treat it. I use an oven and a Brownell's product called ATP to prevent scale. I HT'd a couple blades in the beginning and had a lot of re-finishing to do because of scale, but since finding ATP I rarely have an issue anymore. If I do, it's usually because I left a thin spot or scraped at little off while handling. I make a lot of paracord wrapped survival knives and the whole knife has to be useable and still look good even without the wrap, so I have a lot of real estate to protect from scale. Right? Wrong? I don't know, but works for me.
LRB
Well-Known Member
I agree with Stuart with all, except 1095 should not be taken over 1475° for the quench process, as higher heat is detrimental to the extra carbides that give hypereutectic steels their advantage, and you might cause unnecessary grain growth. There is no oil that will completely beat the pearlite nose. Only brine will do that, but the slight bit of pearlite formation that one gets with Parks #50 and similar fast oils is worth the trade off against cracking for many. In my opinion, 1084 should be treated just as 1095. Heating either 200° over 1414°, the non-magnetic temp, is just begging for grain growth, unless one is beginning a grain reducing heat cycling, and only then. I would add that soaking benefits all steels, insuring a full and even solution and even dispersement of the carbides
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Due to the relatively high manganese content of Aldo's 1084 steel (.803%, as opposed to .35% in his 1095), I have to respectfully disagree with this statement:
I am not sure, and am rather curious, as to what affect adding 15n20 to the mix would change things, HT wise...
From my own limited testing, there is no discernible gain in using a very fast quench (brine, parks 50) with this 1084. Canola oil is sufficient, IMO. That is assuming you get your 1084 from Aldo, or from someone who gets their's from Aldo... there could very well be other batches out there with different manganese amounts.
I am not sure, and am rather curious, as to what affect adding 15n20 to the mix would change things, HT wise...
LRB
Well-Known Member
I would not use brine, and canola oil, while sufficient for 1084, is not quite the equal of Parks #50. I gave my opinion. You gave yours. Aldo's 1084 is not the old typical 1084, but all the 10xx steels benefit more from a fast quench. I would not hesitate to use canola oil, but would prefer to use the Parks if given a choice.
EdCaffreyMS
"The Montana Bladesmith"
All this discussion of quenching made me think back to when I first brought Parks 50 into my shop...... prior to that my preferred quench media was Mineral oil, that I would always pre-heat to 130F when quenching..... I built a new quench tank for the Parks 50, one with heating elements in both ends.....filled it up with Parks, and went to quench a couple of 52100 blades. I pre-heated the Parks, quenched the first blade, and heard "ting, ting, ting" OH NUTS! Several small cracks all along the edge. At first I thought I had overheated the blade, so I did a second one....... "ting, ting, ting" again! Rattin frattin scrattin!!! THEN it hit me, I had been in the routine of pre-heating my quench for so long, that I did just out of habit. The moral of the story? I had gotten to comfortable in my habits, and because I was doing things "like I always do", I ended up with not one....but two wrecked blades. Just goes to show that knifemaking is a constant learning experience..... OH! And the main lesson for me was that Parks 50 SHOULD NOT be pre-heated.
Just goes to show that knifemaking is a constant learning experience..... OH! And the main lesson for me was that Parks 50 SHOULD NOT be pre-heated. 
One
Banned
No, Parks #50 and canola are not equal. In some cases canola may actually be a better choice and in other cases Parks #50 maybe a better choice. Geometry can also play a major role in choosing the better medium, not just the steel type. Basically however, if the speed is equal, the vegetable oil quenchant will stress the steel less than any petroleum based quenching fluid. This is why canola being a *fast* medium also works very well with steels like 01 and 52100, in most cases. You'll get less warping and less chance of cracking than with a comparable petroleum based fluid. This is because of the single cooling mechanism, convection, being quite different. Petroleum fluids have three mechanism with different heat transfer rates. This compounds and multiplies the stresses caused by thermal gradients inherent in knife blades. Canola on the other hand, is virtually pure convection. So you don't get the different cooling mechanisms, (with different speeds) of the petroleum based oils effecting different areas of the blades simultaneously. The effect is that the thinner sections of the blade are already in the fast boiling phase while the thicker sections are still in the slower vapor phase, etc. This is just the opposite of what would be "ideal". In the lower temperature or transformational part of the quench, both types are governed by convection and generally speaking, whichever one has the lowest viscosity will be faster, which is not "ideal" in this part of the quench. From what I've seen of it, the Parks #50 has the lower viscosity. With either one, an interrupted quench and finishing in air, would probably be a good idea, since knife blades are prone to warping and cracking.
Aside from some very real metallurgical advantages, vegetable oils are also much safer, eco friendly and readily available.
Both types have advantages and disadvantages. There are always a few trade offs. It just depends how you want to look at it,… the petroleum based quenching fluids are more cost effective (more stable and last longer), but the initial cash outlay is greater and availability poorer. The petroleum based fluids also have more mechanisms you can manipulate and tweak,… or that *need* to be manipulated and tweaked.
I personally wouldn't opt for the Parks #50, unless it was absolutely necessary. Say for example, on pieces of 1095 (or other very low manganese steels) over 1/8th to 1/4 inch thick at the thickest point,... depending on other variables.
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