Effect of triple quench

May be a dumb question but I'm new to this. When you say triple quenched do you mean you brought the steel back up above critical held it and then quenched and then repeated two more times? Is it supposd to refine the grain structure?
 
Before anybody becomes too awestruck by multiple quenchings ability to refine grain, I would suggest also trying the same experiment with good old fashioned normalizing, which is the treatment designed for this sort of thing.

I put these results of another experiment up about 2 years ago to illustrate the slightly different temperatures required to normalize L6 versus 1084, but they will show this concept quite well also:

L6norm.jpg


1084norm.jpg


The top image image is of L6 overheated and normalized improperly in 1 and 2 but done properly in 3 and 4. The next image is 1084 overheated and then the normalized twice with an image after each one. These photos very clearly illustrate the power of grain refinement whenever the steel is taken properly through recrystallization. The changes made in grain size were from one simple air cooling. Quenching can get it done dramatically as well, but before we get too caught up in the PR of multiple quenching doing things nothing else can we should perhaps check out if there is anything else. Kind of demystifies things doesn't it?:)
 
You always take the mystery out of it, Kevin.

I normalize as a standard part of the forging process.

One is done after the forging and twice more just before the heat treat.

I started doubling up, on the normalizing, when some of my long knives kept warping on me, when they were quenched.

If you make it one of your basic steps, in forging, the rest of the processes are easy.
Thanks for the photos, Kevin.

Fred
 
kevin, are you saying that if I normalize correctly prior to quenching that the benefit of multiple quenches is minimal? I've never tried to inentionally overheat steel to see what the grain size was like. Of the knives I've broken, the difference in grain size didn't seem much different whether I quenched once or 3 times. I always figured it was just inexperience in telling the difference, which is a factor for me regardless.
 
tito said:
kevin, are you saying that if I normalize correctly prior to quenching that the benefit of multiple quenches is minimal? I've never tried to inentionally overheat steel to see what the grain size was like. Of the knives I've broken, the difference in grain size didn't seem much different whether I quenched once or 3 times. I always figured it was just inexperience in telling the difference, which is a factor for me regardless.
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You only need to quench once, if all the other procedures have been done correctly.
When you bring a carbon steel up to critical and let it cool back down, you reduce the size of the grain. [Normalizing]
You cannot over normalize but you can overheat the steel and increase the grain size.
This is why it is important to have good temperature control.

Fred
 
tito said:
kevin, are you saying that if I normalize correctly prior to quenching that the benefit of multiple quenches is minimal? I've never tried to inentionally overheat steel to see what the grain size was like. Of the knives I've broken, the difference in grain size didn't seem much different whether I quenched once or 3 times. I always figured it was just inexperience in telling the difference, which is a factor for me regardless.
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As I understand it, "triple quenching"--as in triple hardening--just induces unnecessary stresses as the austenite converts to martensite.

Quenching just to black or a little below, say 800 degrees F, doesn't do any harm and is basically just a faster way of refining the grain. Normalizing accomplishes the same thing. I use Parks 50 for my quenchant, and I don't want to mess it up any more than necessary, so I just normalize.

Josh
 
tito said:
kevin, are you saying that if I normalize correctly prior to quenching that the benefit of multiple quenches is minimal? I've never tried to inentionally overheat steel to see what the grain size was like. Of the knives I've broken, the difference in grain size didn't seem much different whether I quenched once or 3 times. I always figured it was just inexperience in telling the difference, which is a factor for me regardless.
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There will be grain size range that any steel will be best at due to its chemistry, if you do everything right things will just sort of work and I would suspect this is what you ahve been experiencing, so be happy:thumbup::). There are many things that can happen when you cycle steel in different ways and much of it can be (and is) misinterpreted as fantastic gains when it is most likely only a correction back to normal from an unrecognized undesireable condition that could have been avoided or corrected with routine but properly done heat treating. The least impressive thing any cleaver heat treatment can do is refine grain as it is quite elementary once you understand the process and mechanisms. Both the bladesmiths that obsessively worry about grain growth and the ones that puff themselves up over their ability to control it are really revealing a lack of understading of these same simple processes (this is not a referrence to you at all mstephen, this is the first time I have seen your input on the topic and I applaud your experimentation and desire to see what happens). You can do anything you like to grain size and, as long as you know the alloy and can put the carbon where you want it, correct it in a couple of well controlled heats. Grain size control is one of the first skills a beginner bladesmith should get under his belt before moving on to serious heat treating.
 
JoshEarl said:
As I understand it, "triple quenching"--as in triple hardening--just induces unnecessary stresses as the austenite converts to martensite...
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Yes, but it is those extra stresses that increases the rate of recrystallization, thus it may be possible to get a grain size in one heat that way which may take two with air cooling. so I guess one needs to ask if they want to rush it with the added stress or just take the time to do a good normalization. One also needs to remember that every steel will have a different reaction to these treatments, and each will also have its own temps to work with.

look at the difference in grain refinement in one heat of the L6 versus the 1084 in two! When you have alloying and carbides in the mix everything changes.
 
Fred.Rowe said:
...You cannot over normalize but you can overheat the steel and increase the grain size...
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Actaully with steels like 10XX series and W series you can make it harder on yourself in the final hardening by too much normalizing. With shallow hardening steels increasingly finer grain could lower hardenability to the point that only water or brine will get you there. Also improper cycling will increase segregation and carbide coarsening which will also lower hardenability and have profound affects on the final product.
 
Kevin R. Cashen said:
Actaully with steels like 10XX series and W series you can make it harder on yourself in the final hardening by too much normalizing. With shallow hardening steels increasingly finer grain could lower hardenability to the point that only water or brine will get you there. Also improper cycling will increase segregation and carbide coarsening which will also lower hardenability and have profound affects on the final product.
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I started using the triple normalizing after chatting with Don Hanson.
My long knives [over 10" ]were warping during quenching. After I started using the triple normalizing that stopped happening.
Why do you think this happened?
Maybe the direction I pointed my hammer:D

Fred
 
Fred, for what it is worth I am with you. All my normalizing consists of at least three cycles. It all depends on what you hoping to do. I do feel it is VERY important to have at least one of your normalizations at industry recommended temperatures and then go from there. For so long we have been fed this line of fantastic things from low temp working and how any heat can result in deadly grain growth, that bladesmiths tend to underheat thus often we require more cycles to accomplish many of the desired effects. I can understand it though, spark that steel just once and the higher temps seem pretty intimidating. I used to see it all the time in my intro to bladesmithing classes, the students would burn some steel on the first day and I would spend the rest of the week walking around the forges saying "Get it hotter! Gotta get it hotter!":)
 
Sam Salvati said:
Now I understand when some say "add vanadium to help grain refinement".
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It does work the same way but vanadium is also a very tenacious carbide that will set in the grain boundaries and stabilize them. So it helps with making smaller grains but it also helps keep them from growing in the first place.

This topic is quite fun and stimulating, but I am adjusting to another time zone for a business trip and I need sleep now. I will chat a bit more very early tomorrow morning.
 
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Hi Kevin,
Is the grain size determined on the way up in heat and not on cooling? If I understand that right, does the quench cooling thermal cycling introduce unwanted stress?

Thanks much for any comment, Craig
 
I was simply showing how i reduce grain structure.I didnt realize i was being at all mystical.I started quenching to reduce grain size after talking with al pendray and watching howard clark quench cycling on a seminar dvd.After getting a copy of verhoevens book it was pretty clear why "ultra fine grain structures were obtained".But i guess thats mystical to some.
 
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Kevin, so instead of using a large hammer to break the steel molecules along the cutting edge into smaller molecules I can merely normalize to refine the grain? ;)
 
Ditto exactly wht Don said, mstephen I would implore you to read all of my posts, and will even repost some that obviously got by you:

...(this is not a referrence to you at all mstephen, this is the first time I have seen your input on the topic and I applaud your experimentation and desire to see what happens)....
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You didn't label your posts or thread "grain reduction", you went with the more controversial catchphrase of "triple quenching", due to propaganda surrounding one they are not the same thing and my point was to show that. Some pretty tall tales have been attached to the latter with no attempt at explanations and accurate proof of cause and effect instead of poetic sales pitches and vague references. Normalizing and thermal cycling on the other hand are very straight forward operations that are quite easily explained, I know Mr. Pendray, and Mr. Clark, and I have read Verhoeven's books (yes he has more than one) and I am confident that they would very much agree with me on this point.

Once again, I didn't say you were being mystical, but in the future if you want to avoid that confusion you may want to avoid using the words of the mystics.
 
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