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Roger
12-15-2010, 12:36 PM
New guy dumb questions....

Quenching W1 in water brine? Just water with salt? Ratio? Iodized or not, rock or sea? Temperature of the water?

Air hardening. Just room temperature air, hang it in the corner till cool?

Thanks.

Kevin R. Cashen
12-15-2010, 08:50 PM
While W1 is designated "water hardening" that is for much larger sections than knife blades and water based quenchants can actually be overkill, resulting in distortion or cracking. There are those who will tell you that they have ways of quenching in water without any of these problems but these methods almost always involve under soaking to avoid the stresses of full hardening. In sections under 1/4" you should do fine with a fast oil, find a very low viscosity oil that is nice and clean and heat it to around 130F. The best would be an actual quenching oil, but I will assume you are not ready for that level of commitment in supplies so if you must do with an alternative canola oil may get you by for now. if you would still like to go with brine, the proper concentration is around a 9% solution in room temperature water, some will tell you to heat it but that will only increase the problematic vapor jacket, all you really want is to avoid it being too cold. Rock salt should work just fine.

W1 is not an air hardening steel and will not respond well to that treatment, however if you have some "A" series or stainless alloys that you were thinking of trying it on, still room temperature air is the standard.

rob45
12-16-2010, 01:22 AM
if you would still like to go with brine, the proper concentration is around a 9% solution in room temperature water, some will tell you to heat it but that will only increase the problematic vapor jacket, all you really want is to avoid it being too cold. Rock salt should work just fine.

I'm still new to this, too.

Why would one want to brine quench?
I have heard it is more severe than water. Or is it faster than water but not as severe?
And when a 9% solution is mentioned, is that percentage based upon volume?

Thanks,
Rob

Kevin R. Cashen
12-16-2010, 07:38 AM
I'm still new to this, too.

Why would one want to brine quench?
I have heard it is more severe than water. Or is it faster than water but not as severe?

Water based quenchants (water, brine, hydroxide etc...) all suffer from two issues, an extraction rate approaching 4000F/second and, but more problematic, perhaps the largest vapor jacket of any quenchant (212F is a pretty low vapor point). The two combined makes for a treacherous cocktail, when that vapor jacket begins its collapse. Imagine one area of the blade totally shielded from cooling by the Leidenfrost effect, while one small section,within it or beside it, suddenly gets exposed to a 4000F/second cooling. If you have full solution and can achieve full martensite, any part cooled out of sync with the rest will expand on orders of magnitude much more than the surrounding metal, somethings gotta give.

Adding brine, or other solutes, to the water will cause instant crystallization on the blade surface which will destabilize the vapor jacket in a more even fashion. This solution would be fine for parts with symmetrical or even cross sections but knives by their very nature have thin parts and thick parts, when one hardens and expands totally out of sync with the other you get distortion or cracking (that is exactly how Japanese swords get their curvature). You can compensate for that by undercutting the soak and not putting enough carbon into solution and limit the expansion... but also the maximum hardness. Or you can find a quench medium that will allow you to have it all.


And when a 9% solution is mentioned, is that percentage based upon volume?
To do it by weight would be quite skewed to the water.

Roger
12-16-2010, 08:51 AM
I've been reading a section that deals with quenching oils and some stuff from McMaster Carr is mentioned. I can easily get some from there but how much is actually required? I'll be using a container large enough to dunk to just the tang. Will that offer enough cooling quickly enough or will the oil tend to get hot and not work well with only that much volumn?

rob45
12-16-2010, 10:06 AM
Water based quenchants (water, brine, hydroxide etc...) all suffer from two issues, an extraction rate approaching 4000F/second and, but more problematic, perhaps the largest vapor jacket of any quenchant (212F is a pretty low vapor point).

Adding brine, or other solutes, to the water will cause instant crystallization on the blade surface which will destabilize the vapor jacket in a more even fashion. This solution would be fine for parts with symmetrical or even cross sections but knives by their very nature have thin parts and thick parts, when one hardens and expands totally out of sync with the other you get distortion or cracking (that is exactly how Japanese swords get their curvature). You can compensate for that by undercutting the soak and not putting enough carbon into solution and limit the expansion... but also the maximum hardness. Or you can find a quench medium that will allow you to have it all.

Kevin,

Thank you for the detailed response. I sincerely appreciate it, as I know you're very busy.

Here is how I interpret the information thus far (PLEASE correct me if I'm in error):

1. If using a water-based quenchant, brine is less likely to result in distortion/cracking than plain water.

2. Water-based quenchants are fine for, say, hammers and anvil faces, etc., but not so ideal for items with edges due to reasons you mentioned.

3. Concerning the example of Japanese swords, my belief until now was that the differential hardening process through use of clay coating was what created the sori (curvature). Inferring from above, it is not only the insulating properties of the clay, but just as importantly (maybe even more so) the quench medium being used
I believe the primary goal was to have a hard edge with a tough (soft) spine, and the curvature was simply a byproduct of the process being used.
Now, the curvature is desired for aesthetic reasons, not merely a byproduct of obtaining function. Is this why the swordsmiths continue to water quench, or is it merely "clinging to tradition"?

4. I do intend to obtain specified quenching oil as I advance in this craft, but I also want to learn as much as possible about heat treating and quenching during that advancement.


I do not intend to hijack Roger's thread; matter of fact, I believe this is good knowledge to anyone.

Thanks,
Rob

rob45
12-16-2010, 10:18 AM
I've been reading a section that deals with quenching oils and some stuff from McMaster Carr is mentioned. I can easily get some from there but how much is actually required? I'll be using a container large enough to dunk to just the tang. Will that offer enough cooling quickly enough or will the oil tend to get hot and not work well with only that much volumn?

I've wondered about that, too.
A gallon per pound of steel? Or what? Surely there's a "rule of thumb".
Certainly the container needs to be large enough to allow moving the blade (agitation).
I would think that moving the blade through the quenchant is important, so not only "how much oil for how much steel", but also shape of container. In other words, the container large enough to hold the blade and move it through the quench may hold more oil than what is "theoretically" needed.

Roger
12-16-2010, 12:07 PM
I do not intend to hijack Roger's thread; matter of fact, I believe this is good knowledge to anyone.
Thanks,
Rob

Don't worry about that. knowledge means a better knife. Thanks Kevin & Rob.

Kevin R. Cashen
12-17-2010, 08:25 AM
...1. If using a water-based quenchant, brine is less likely to result in distortion/cracking than plain water.

Theoretically, yes, but it doesn't always work out that way for us due to the size and shape of our steel.


...2. Water-based quenchants are fine for, say, hammers and anvil faces, etc., but not so ideal for items with edges due to reasons you mentioned.

Water is cleaner, easier and cheaper than almost anything and yet almost all industry has abandoned it for expensive, messy, and more hazardous mediums. BUt in the long run it is cheaper to keep all your parts instead of sacrificing a percentage to distortion and cracking. Typically industry has handled this by developing the alloy around the problem and not the quench medium, first they developed oil hardening steels and the "W" and 10xx series were phased out, now, tiring of the liquid hassle altogether they are opting for air hardening alloys and steels like O-1 are being replaced. Even the very skilled guys doing Japanese style blades in water will admit that they lose as much as 1/3 of their blades to the perils of water, I personally can't make a living doing that, and I also have tools to allow me to see inside the steel that "appears" to have survived the water only see the micro-defects from it.



...3. Concerning the example of Japanese swords, my belief until now was that the differential hardening process through use of clay coating was what created the sori (curvature). Inferring from above, it is not only the insulating properties of the clay, but just as importantly (maybe even more so) the quench medium being used...

Absolutely, quench such a blade in oil and it starts to curve in the opposite direction, reverse sori is a big aggravation for many smiths when they first make the transition to oils for such blades.


...
I believe the primary goal was to have a hard edge with a tough (soft) spine, and the curvature was simply a byproduct of the process being used.
Now, the curvature is desired for aesthetic reasons, not merely a byproduct of obtaining function. Is this why the swordsmiths continue to water quench, or is it merely "clinging to tradition"?

Several things going on here, different parts of the tamahagane bloom with different carbon levels were often combined in the blade to overcome brittleness as well as the differential hardening. The curvature may or may not have been unintentional at some point in antiquity, but it is much less aesthetic than essential to function on a single edged blade like the katana, the cutting action is greatly enhanced in the style of cut with that type of sword.

Now as for tradition or necessity of water, here comes the one crucial point that most people overlook when thinking of water quenching because of tradition. Ancient steels, like bloomery steel and tamahagane had no intentional alloying whatsoever, they were simple iron carbon systems, and thus they were incredibly shallow hardening even when compared to W1 or 1095. W1 or 1095 has extra things in it, whether listed or not, and would not survive many of the same treatments that a piece of bloomery steel could. The downside to this is that those simple iron-carbon steels did not have the same impact toughness that modern steels do (trust me they don't, I work with them a lot these days) and so all you could do is adjust the hardness levels in order to gain toughness. Thus you went with a lower Rockwell all around, differentially hardened, or welded together different hardness levels. Making swrods today you can quench an alloy in oil and temper it back to 58 HRC and get 3 times the toughness of those old steels at a much higher hardness. So the tradition is not so much in the water, but in using the ancient steels.

Roger
12-17-2010, 10:40 AM
I can understand what Kevin is saying when talking about steels being phased out as better one's are developed for workability and ease of quench. I have been researching steels and it seems to me that for a person just starting out why not begin with W2? From what I can tell it's reasonably easy to work and hardens well. I actually got a bar from Carr and plan on spending the weekend carving on it. Since it hardens in air is air hardening like quenching in other mediums. Is there a certain temperature air to harden it in? Do you cool it slowly or just draw it out of the oven and hang it in a corner till it cools? Can the air be to cold or to hot? Should it be hardened more than once?

Kevin R. Cashen
12-17-2010, 02:47 PM
... Since it hardens in air is air hardening like quenching in other mediums. Is there a certain temperature air to harden it in? Do you cool it slowly or just draw it out of the oven and hang it in a corner till it cools? Can the air be to cold or to hot? Should it be hardened more than once?

:31: Are you sure you mean W2? W2 or W1 are definitely not air hardening, in fact of any steel they are the most opposite extreme from air hardening. Air cooling W2 is called "normalizing" and won't get you anything more than pearlite (soft stuff), perhaps 40 HRC if you are lucky.

Roger
12-17-2010, 02:57 PM
My bad, it was a typo A-2 was what I meant....and another question. Should A-2 be normalized a few times prior to hardening?

LRB
12-17-2010, 03:56 PM
Depends on if you are forging or grinding. If grinding, no. All the A2 I get is spheroidized annealled, and ready to harden when you get it. You do have to give it a long pre-heat stress relief before bringing to quench temp. I stress relieve at 1350 for 45 minutes, then it goes up to 1775 for 45 minutes. I quench by holding in front of a box fan on high speed. Temps and times will vary according to whose tables you read, and who you ask, but this works well for me.

Roger
12-17-2010, 04:42 PM
That helps a lot, thanks.