Tripple quench, once and for all. Maybe

Tom Lewis said:
...One more question, would L6 be a good steel to try the triple quench with, or should I stick to 52100?..
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I want to make it perfectly clear that I am not making any statements for or against the technique, but Tom asked a simple to answer question. Tom, due to its alloy makeup and carbon content 52100 has a better chance of showing affects, for better or worse, by multiple cyclings at different heats. Metallurgist have used it often to study the affects different treatments can have upon carbide precipitates.
 
Tom Lewis

I have spent some time over the last few pages of this topic thinking about what type of test I would like to see someone perform.

I have come to this conclusion:, That there are two good testing systems to employ.
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First, there is the "Double-blind" test where you do both test knives the same way for one quench, then place both knive in a box, reach in without looking, and take one out and do the other two identical Heat-treatments on that knife.

Then send the knives to someone else without telling them what knife is which.
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The Second testing method is the "Throw everything at it" type of test.

In this test you stay completely aware of the knife that is going to be triple quenched, and you use any type of Heat-treatment you can think of. Do anything to the blade that you wish to test out.

Then on the other blade just do a very boring single quench the way they talk about in books. Again send the two blades to someone else without telling them what happend to each blade. and let them see if they can spot any differences.
 
Not intending to be facetious, but my favorite blade test is to take it elk hunting and see if it will still cut after field dressing, skinning and quartering an elk. Tough hide, hair, cartilage, meat and some bone will be the acid test in my mind.
 
For what it's worth, I have been doing some testing with a friend and fellow bladesmith with 52100 and different heat treats. We sent two samples to a lab in Ca. to get a grain size. Sample one was normalzed three times, then soaked at critical temp. for 5 mins. before quenching. Sample two was normalized one time, heated to critical then quenched in water followed with two more quenches in oil. The grain size of both pieces was 13. The test pieces were half inch square and 3 inches long. Maybe if they had both been thinner sections, the grain size would have been smaller. Sample two had no retained austenite, better carbide distribution. Sample one had smaller carbides.

For me, the bottom line is test, test, test to determine how I can make the best knives I can in my shop, with my equipment.
 
shgeo said:
Not intending to be facetious, but my favorite blade test is to take it elk hunting and see if it will still cut after field dressing, skinning and quartering an elk. Tough hide, hair, cartilage, meat and some bone will be the acid test in my mind.
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I am with you completely on that one. Most of my testing is for tweaking the heat treating, I leave the assement of the quality of my blades to the folks using them. Around deer season I enjoy talking to anybody local who has my blades . It can be incredibly subjective, but so much about why we like a particular knife is. Many folks are probably also commmenting on the ergonomics and handle design as much as whats happening at the microscopic level, when they say a knife cuts well.

For pure torture testing, I also believe that dropping a knife off in a busy kitchen for a while, is actually asking more of it than what most camp knives should have to endure. The kitchen environment has to be one of the most destructive on knives, in my opinion.
 
working on my new knife tonight. Finished on the buffer. was very happy with this one. could not wait to show it to my wife.

turned off the light, reached for my knife in the dark. bumped it, heard it hit the cement floor of my shop.

Now it was still dark in the room, I had no idea where my knife had come to a rest, But there is one thing I know 100% for sure....

I know when it hit the cement that it landed on the point.....

(They always do)
 
DaQo'tah Forge said:
working on my new knife tonight. Finished on the buffer. was very happy with this one. could not wait to show it to my wife.

turned off the light, reached for my knife in the dark. bumped it, heard it hit the cement floor of my shop.

Now it was still dark in the room, I had no idea where my knife had come to a rest, But there is one thing I know 100% for sure....

I know when it hit the cement that it landed on the point.....

(They always do)
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well ... did it brake or stand that tesT? :)
 
Mete or anyone else.

Tonight I did a bit of work in the forge.

I hammered down a 1& 1/2 inch Load Shaft into a blade. The blade is still connected to the shaft and while I was working down the tang, I decided to try that cold-oil quench this time as an experiment.

I heated to non magnetic near the finishing of the tang, then heated it a bit hotter, then ran outside to the 6inch wide/ 3 foot long pipe I have filled with mineral oil and jammed the blade/shaft down into it.
There were tons of smoke, but no fire this time.
I did this same thing 3 more times as I finished the tang.
I then normalized, then placed the heated blade in Vermiculite to anneal over night.

Comments?

I still have to cut the blade free of the rest of the shaft in the morning, and there will be a bit more with the forge and hammer. Here is my question.

I have a clear idea now, based on what you experts tell me about the very importance of the last heat treatment before the actual heat-treatment and quench to make the blade edge hard.
I wish to do this next to last heat treatment the correct manner so as to set my self up later better.

QUESTION: What do you suggest is the best way to do the heat treatment that comes just before the real hardening of the blade treatments?

Also, to heat the steel when I quench to harden the blade I use my forge. I heat to non-magnetic, then race to quench before it can cool at all.
But I also hear much talk about allowing the steel to sit for a few moments at the right temp.

My last question,
QUESTION: , do I have to wait with the final heating of the blade before the last quench, or can I just heat to non-magnetic and quench right away?
 
Is that 6" dia pipe your normal quench tank ? if so it doesn't give you much room to agitate the blade...Considering the steel, 5160, you shouldn't need anything more than a normalize before hardening......When you are hardening the blade, heating to non-magnetic transforms the ferrite to austenite but you also want to dissolve the carbides and diffuse the carbon. This takes some time and is called soaking. 10 minutes will be fine.
 
mete should the same thing work good for 1095? normalize then heat and soak, then quench 1 time. if so how long should i soak it for 3/16" 1095? if i soak too long will the grain begin to grow? i know if i over heat it it will right? what would be the best temp to soak it at?
 
how long at that temp (1525 degree's Fahrenheit is 829.44 degree's Celsius) would it be before the grain would start growing? or is the grain growth more prone to higher temps?
 
Mete.

Thank you so much for taking the time to help us new guys out.

After reading your post, I went back to my post and saw how much I have not wrote what I was really seeking to ask you about.

I try again.

First, I talked about cold-oil quenching during the forging down of the tang area of the future knife.

I made a 6-inch wide pipe into a vertical quench tank due to one very important reason. FIRE! When I tried a few times to jam my red-hot blade into my normal quench tank that I built (Just like Ed Fowlers) I had a monster fire to deal with. As this fire happens inside my shop I had to come up with a new idea. The 6-inch by 3-foot deep pipe that I have filled with oil allows me to run out side to where I have it positioned, and then just drop the red-hot blade into the oil and back away from all the smoke. The depth of the blade in the oil keeps the chance of fire low.

Based on what I have read in this forum from you and Kevin, I sure thought that a quench-while-still-forging the blade was helpful for some reason.

QUESTION; based on what you read now, is my use of this type of pre-hardening quench, Pointless?

Second: You guys keep saying that the success of that final heat-treatment, (where I make my blade hard along the cutting edge), all depends on the type of heat treatment that happened just before that one. Well the last thing I do now before I start to use my belt grinder is to ANNEAL by heating to non-magnetic and then burry in Vermiculite overnight. That's it! The only thing I do later is to actually heat and quench to harden the blade for the last time. (After I finish the belt grinding)

QUESTION: What do I do as the last heat-treatment before I start to use the belt grinder? How to I set things up so that later when I do the final heating and quench, that things are all set-up correctly?



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Just to make sure you understand,,,I use two different types of quench tanks.

The 6 inch pipe is just for doing the cold-oil quench while still working on the blade.

and a normal quench tank with a little table in the oil that I make go up and down to only quench about 1/2 my blade in the oil on. (Just like Ed Fowler shows in his video). and I use this quench tank to do the final edge hardening quench.
 
Terry...

Just to make sure I understand your post....I have to ask....

Are you heating a first time and allowing to cool fully and this is what you call "Normalize"?

Then are you heating a 2nd time, (perhaps hours if not days later) and seting the blade in the forge for 10 min and this is what you call the "soak"?

and then, (here is the important part)
and then do you mean you waite until the blade is cool? and then later, perhaps hours if not days later, you heat again and quench to make the blade hard?
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My problem is understanding this word "soak"....is it going on just before you quench?,,,or is it going on way before you heat for the last time? (like hours if not days later?)...and the your blade cools after the soak?
 
DaQo'tah i normalize by heating the blade to 855 degrees celcius (1575 degrees farenheight) and letting it sit in the forge at that temp (soaking it) for about 30 seconds (i did not know i needed to soak longer than that at that temp) then air cooling til room temp. (when it is in the forge soaking i am constantly moving it back and forth to even the heat in it. i have been doing this 3 times. for quenching i had been heating to 800 degrees Celcius (1480 degrees farenheight), soaking it about 30 seconds and immediately quenching it in vegtable oil i have in an ammo box at an angle to my forge (less that 2 feet away). i use the ammo box becaus it is water and air tight. if it was to catch on fire i could close the lid to put it out. i have not had it catch on fire yet that i had to do that, sometimes if i edge quench it will flame a little but i just push the blade on down and it goes out. also not a lot of smoke, and what little smoke there is smells like frech fries or something.

mete does that sound like it will make for a nice grain or would soaking it for 10 minutes make it better?
 
Terry,

I have some numbers for 1080 steel. (From the 'book' I posted.)

It appears that in 2 seconds at 1450 you get .5% Austenite. In 8 you get 99.5% However to completely desolve the carbides you need about 2 minutes. For a completely homogenous structure you need more like a hour and half.

What is best for a knife, I don't know.


Still I find it interesting to see the effects of soak times. Temp swings of 100 degrees makes a huge difference too.

I'm beginning to see why personal experiments are sooo important. It isn't that steel is different at your house than mine or the metallurgy is inexact. It's just there are sooo many factors it's tough to predict anything.

Steve

FWIW, I made a 5160 blade yesterday. 10 minute soak at 1580, quench in 140 degree fast quench oil. Made a real nice blade - still testing.
 
First safety - one of the advantages of using proper quenching oil is that they have a high flash point and therefore less likely to ignite. You should have a metal cover for your quench tank which you drop immediately on the tank in case of fire such as Terry's ammo box. A large CO2 extinguisher is necessary too........Terry , grain growth is a time and temperature dependent thing though more sensitive to temperature. Within reasonable times and temperatures ( ~ 1525F and ~10 min) there will be no problem. We need the soak time to thoroughly dissolve carbides and diffuse the carbon throughout the matrix .If that is not done the martensite will not be homogenious nor as strong as it should be......D F, I am always frustrated when I see people do complex heat treatments to 5160 because the steel is certainly what would be called simple and 'forgiving' to heat treat.I could see maybe one quench during forging and normalizing ,not annealing as the last step before hardening. But you should always experiment. Treat samples in different ways then check hardness ,then break the sample to compare grain size.
 
METE....dont I have to anneal before I use the belt grinder to first work the blade into shape for the final Heat-treatments?
If the steel is hard at all, wont it burn out my sanding belts?

How about this order..

1 - forge shaft into a rough blade shape.
2 - as I forge tang, quench one time in cold oil
3- normalize
4 - Anneal so steel is soft on my belts
5 - use the belt grinder to work the blade close to final shape,

6? - normalize one more time

7 - heat and edge quench
8 - temper in kitchen oven for 2 hours at 325-350
9 - temper again
10 - finish blade with belt grinder and buff
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Mete, are there any problems with this so far?

this would be more simple ...anything left off my list?...something un-needed?

I do try to test my blades against a common file...thats why I could not find support for a 3-quench heat treatment.

I have on the other hand found some support with my file for switching from the O/A torch to the forge to do the heating of the blade for the last important quench. The forge-heated blades seemed to get harder.
 
Hi, first time posting here though I've been reading here for a while and post on a few other bladesmith boards...

DaQo'tah, I noticed one thing when you described your process that I think could be a problem, and that's the "running outside" part. Most steels need to be brought down to 400 degrees from critical in 2-5 seconds or so. I have my quench right next to my forge and sometimes just the time it takes to check it with a magnet ruins the quench, running outside with the moving air (actually the knife is moving, but same effect) cooling the blade as you go makes it likely to make a good quench impossible.
 
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