multiple quenching, normalizing before quench, etc

[Scott Roush]

some things came up when i was searching the forums on another site.

multiple quenching:  i noticed it being done at the smokey mountain hammer-in.  so... who does it here... and why and when?

normalizing right before quenching: good idea or bad?  it is clear that normalizing right after forging is the right thing to do. but i'm starting to hear whispers that you shouldn't do it right before the quench.  i saw reference to this in kevin's recent post... and also in Cashen's discussion on 1095 heat treat on blade forums.  is there anything to this???

[Scott Roush]

and while we're at it.. how about interrupting quenches?  do folks here do that??

[Ragnarok Forge]

Multiple quenching is redundant in my book.  Interuped quenching is something I am fiddling with right now but do no have figured out fully just yet.  Wiser minds will weigh in shortly I am sure.  I do have to say, I only rarely have a problem hitting the hardness I am looking for with a single quench.  I am using interupted quenching to create multiple hardening lines or hamons in the steel for the visual effect more than anything.  

In my view normalizing is a requirement in my shop.  A lot of stress is created during the forging process and a triple normalization process right after forging reduces / removes all the stresses in the steel. Which prevents blade failure when you quench.  We have all heard that horrible snick sound of a cracking blade. all to often.

I frequently finish my last normalizing step, let the blade cool to air temp, then do a quick grind to remove the scale, plus a  fast surface grind to 150 grit.  Then it is right on to quenching.  I have never noticed any problems or steel failures due to the short time frame.

Others folks may have different experiences or knowledge on this subject.  I can say that tempering right after quencing, as in immediately is always a good idea.

[Scott Roush]

the more i think about it.. i'm wondering if i misunderstood something.  if it completely cools after normalizing why does it matter when it's done as long as it follows forging?  although there was mention of spheroidal annealing (as opposed to lamellar) following the third normalization cycle to remove even more stress and to facilitate grinding and drilling... and then quench. again... this was all in reference to 1095 which apparently remains fairly hard after normalization. i take it that some people normalize again right before the quench?

i take it you must be edge quenching then?

[Lin Rhea]

I do practice normalizing before I quench. I do it because I want to make sure the grain size is reduced as far as I can get it, within reason. This is a standard for me now. The benefits will vary from steel to steel, but as long as I can get a cosistant result, at least I feel like I have brought each blade of a given steel to a standard of condition before proceeding on to the next steps. Whether I normalize after forging or immediately before I quench the ground blade or both is largely up to my availablity of time. Lin

[Ragnarok Forge]

I do both edge quenching and full blade quenching depending on what I want out of the individual blade.  I have recently been working on bringing out a hamon and for that I am doing a full blade quench with a clay coating.  I do not want a sori ( positive curve ) in the blade so I am doing a tip first full blade quench.  It has worked pretty well so far.  

I edge quench the majority of the blades I make right now.  I am finishing up the handles on multiple hunting / skinning knives for the Western States Rondevous and all of them were edge quenched.  

I think we all need to talk Lin into holding a Trad Gang Knife Workshop where all of us backyard knifemaking guys can throw up some cash for Lin's time, take a flight to Arkansas, and spend a weekend / week learning from the master. Throw in some barbeques and maybe a hog hunting day and it would be game on.  

Maybe we can talk him into a little traveling.  I can provide a forge, anvil, etc...  We can set up shop in hunting camp.  I will throw in a Salmon / Steelhead fishing day and some Elk / Blacktail Deer hunting at the Washington coast if Lin wants to come out and visit the West Coast to put on a knife work shop.

[Scott Roush]

i'm in Clay.  i'm tired of sweetwater steelhead!

Lin... how about interrupting quenches and multiple quenches? do you mess with any of that???

[kbaknife]

The purpose of the interrupted quench is to stabilize temps throughout the blade's varying dimensions before hitting Mf (martensite) finish.
You want to get the steel's temp below about 900-1000 degress so it won't revert to pearlite, but you want, as well, to stay ABOVE 400, or the steel will miss a fair amount of martensite.
As long as the steel temp remains above about 400 degrees, it will also be quite soft allowing for straightening before re-entering the quench media and taking the steel temp on down and the steel can cool evenly.
In this thread - so far - you have tossed around a LOT of terminology without discussing steel types, and/or austenizing methods.
The higher alloy types, like 5160 and 52100, WILL benefit from the multiple quench so as to reduce retained austenite, which can be a problem with steels normally requiring long soak times.
If you have taken a hyper-eutechtoid steel (above 0.84%C) to ABOVE non-magnetic and then slow cooled, it may very well be annealed to the point where it is capable of being drilled and tapped and threaded, but that steel now needs a MUCH longer soak time at austenizing temp to get every thing back into solution.
That another good reason for having a heat treating oven in that you can do a sub-critical spherodizing anneal where all of the carbon is pooled into small spheres (hence the name "spherodizing" anneal) allowing for easy workability, but then the carbon is in such a position that it doesn't need a long soak to immediately go into making martensite.
I spherodize every single steel I forge, after post-forging thermal cycles and reducing heat quenches to first create martensite and to then reduce grain size.
Lin mentioned an important subject about reducing grain size "within reason" since the smaller the grain size the more you reduce hardenability.
As well, make sure you are saying what you mean when you mention "normalizing". Normalizing refers to taking the steel way above the austenizing temp for that steel and then cooling back to room temp.
"Thermal cycling" is best done in reducing heat steps, first to well above austenizing temp, then to just above non-mag and then right to non-mag, and only cooling back to a black heat (1000) between cycles.
Kevin Cashen's dissertations on all of this are really worth reading, as long as you define the words within and really get an idea what he is saying.
I'll bet I find myself re-reading them about every 3-4 months.

[Lin Rhea]

Karl,
       Kevin Cashen's theories are interesting reading and I humbly take his word for it. Although I do have to slow down to a mere crawl reading it to allow time for the big words to soak in.
       I went back and read the thread that Scott mentioned in his first post. The one on bladeforums. What I read helped me to understand something that has been happening to me. You just mentioned it. When I thermocycle 5160, I find it does need more time at critical. If I just come up to temp and quench, it wont fully harden. It will harden, but not like I want it.
      In this case, I always re heat and quench again. This might take three times, but it will eventually get fully hardened. This verifies what Kevin was saying. Lin

[Ragnarok Forge]

I have been working with simple high carbon steels, specifically 1080 and 1084 for the knives I have been making and have had good success with achieving the hardness levels I am looking for with a single quench.  I was just thinking about branching out into 5160.  It sounds like I need to buy that knife kiln I have been thinking about to get the steel set up for proper hardening.  Right now I do not have my forge set up properly to allow true consistency in temperature over a fairly long soak time.

kbaknife,  You and I are refering to the same thing when I was discussing normalizing.  Do you have a good link to Kevin's dissertation?  I would be very interested to read it thru.

[Scott Roush]

karl.... this all started by my investigation into heat treating 1095.  i believe that all of cashen's discussion was mainly referring to this steel as well (which i mentioned above).  but some of the things discussed (like multiple and interrupted quenching) got me to wondering about the general applicability to those techniques.. especially after i saw the fellas in the 'battle of the bladesmiths' doing multiple quenches.  however... i don't know what steel they were using. i wondered at the time if it had something to do with the size of the gigantic blades they were working on... or if they were simply correcting warpage.

now that you mention it... cashen was making reference to the soak time above critical required by 1095.

i was using 'normalization' in regards to reducing grain size through cycles of 'decreased heats' as you say.

thanks a bunch karl.... i know i have a habit of getting into things a bit over my head... but, i'm learning from it!

btw... in cashen's discussion, he provides a method for doing the spherodizing anneal with a forge.. for those without heat treat ovens. although i assume it is only appicable to 1095...

[Lin Rhea]

Kevin was talking about 1095, but you can bet every high carbon steel we would make into a knife can be done in a forge. An oven is better in some cases where control is lacking in the forge, but there have been a lot of good knives made by folks who know their steel and done it in a forge. Oven or forge, you have to know your steel. Lin

[kbaknife]

It's all right here:
"The Process and Principles of Quenching"
 http://www.bladeforums.com/forums/showthread.php?t=639019

and
"Working the three steel types"
 http://www.bladeforums.com/forums/showthread.php?t=673173

(Hope I don't get in trouble!)

[Jeremy]

Originally posted by kbaknife:

Hope I don't get in trouble!

I won't tell if you don't  

Good info in those threads!

[Ragnarok Forge]

Thanks for posting those. I will be reading thru them this weekend.