Quenching: Water or Oil?

[30cal_Fun]

Hi,

I have been making blades for some years and I try to get as close to the Japanese way of making knives and swords as possible.
I differentially harden my blades to get a Hamon, and so far have always used water.

However, I read a lot about people quenching in other liquids like oil and even brine. I know that some steels quench-harden better in oil, but I never really understood why. Does it have to do with heat distribution when the hot blade meets the liquid, the chemical composition of the liquid, the viscosity, or even how fast the temperature of the liquid itself rises???

So; which factors make up the choice for the appropriate liquid? will water-quenching give a better Hamon on steels like 1075 or 5160?

Let me know what you think,
Louis

[Frank Turley]

Yes, no, maybe, and I don't know.

I spent a few days with Yataiki, a Japanese saw and tool maker, and he stirred the water with a red hot rod and hand tested the temperature before quenching. I'm not sure about the hamon, but I assume that all blades with hamon are quenched in such water.

There is an old story about the Japanese apprentice who continuously questioned the blade master about the proper temperature of the water for quenching. The apprentice was becoming pestiferous regarding the subject. One time when the master was preparing to quench a blade, the apprentice could contain himself no longer and dipped his hand in the water. The old man cut off his hand.

Yataiki knew that story, and I asked through an interpreter if I could test the water without getting my hand cut off. We all had a big laugh, and Yataiki said that I could put my hand in the water. The water was tepid.

As regards other quenchants, we do whatever the metallurgist says to do for a particular steel. I'm not concerned with hamon, so on 1075, a plain carbon steel, a metallurgist would say to quench "thin sections in oil." To me, that means a knife. When you look up the specs for 5160, it is oil hardening because of the silicon, manganese, and chromium alloying.

In terms of speed, in a small shop situation, brine is the fastest quench, because it throws scale allowing the liquid to contact bare metal right away. Water is next fastest for somewhat the same reason, though not all scale may be thrown off of the workpiece. A steam vapor blanket is formed around a hot piece when it is submerged in liquid. It is momentary, but with oil, it is prolonged compared with the water quenchants. The vapor acts as a brief insulator, thus slowing the quench a bit. With thin cross-sections like a blade, oil is recommended by metallurgists over water, even though the steel is sold as water hardening, such a W1 or W2. With oil, there is less chance of warpage, and you still get hardening. Ambient temperature brine or water may be too severe for thin sections, thus causing cracks, breaks, or warpage. Of course, air hardening steel has the slowest type of hardening.

If you are purchasing tool steel, you should get the heat treating specifications that go with the tool steel.

Some tools are agitated under the liquid to help shake off the vapor blanket and to allow a fresh supply of quenchant to hit the piece from all angles. I'm fairly certain that Japanese blades are not agitated. The tepid water and the vapor blanket duration are proper for their quenched blades without agitation.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[30cal_Fun]

Thanks for your input, any experience is welcome to me.

I like old stories like this, they have a pinch of humor in them, but always some valuable lessen too.
Japanese smiths always quench in water, even master smiths use regular tap water of ambient temperature. And with great success for over 1200 years.

However, I can see your point, steels of the 10xx series are well suited for water quenching. If the blade edge is left about 2mm thick before quenching, the blade won't crack that easily. 1070/1075 steel is probable the simplest and closest equivalent we have to the Tamahagane Japanese smiths use.
5160, because it is a spring steel has very different properties because of it's chemical composition. If I am not mistaking, throwing of scale isn't what I want because the blade is coated with a layer of clay. Since I am going for a Hamon, wouldn't it be best in my case to go for a fast hardening quenchent? I am not familiar with brine, so I will stick with plain water first and see what happens. If all my blades crack, I can still turn to oil.
What would be a good (and easy to get) oil to use for quenching?

one last question: what do you mean with "Some tools are agitated under the liquid"? I do not understand exactly what you mean with agitated.

Louis

[AmiRasco]

I'm not an expert on the subject, but as far as I know, oil, even cooking oil would do a better job than water because of the boiling point.
When you dunk hot metal into water, the water "flash" boils which creates pockets of steam between the water and your blade, bubbles running around on it and such which could very much give you an uneven quench. That's not to say that water dosn't work, the Japaneses have been using water for the worlds most revierd blades we know.

So if you're gonna use water, use a relatively large quenching tub so you can keep your blade in motion while inside the water so you get constant contact between your blade and the water.

http://www.youtube.com/watch?v=oijgODuKzeo&playnext_from=TL&videos=F1HqH1-K_IY

This guy is quite informative in his vid's, maybe he'll be of some help.

Enjoy,
Ami.

[ThomasPowers]

Actually 1050 is much closer to traditional japanese sword steels than 1075.

gotta watch out for "tradition" Traditionally smiths used real wrought iron for about 2000 years before the Bessemer converter and mild steel came along less than 200 years ago. Real wrought iron is often worked at a lemon yellow to white heat. Work your modern steels at those temps and watch the sparklers!

[thecelticforge]

What are you using to coat the blade with before you quench it?
Do your blades have an iron core?
I would try experimenting with a few blanks first.
So far it looks like Frank and Thomas are offering the soundest advice.

[30cal_Fun]

For the past years I have mainly been shaping by stock removal. I have been using simple steel that you can get everywhere here in DIY stores, it has a black coating on it and comes in 2 meter strips of various shapes and sizes.
I have absolutely no idea what steel this is, but from spark tests I think it is a low to medium carbon steel, I differentially harden it and it gets hard enough for files to have trouble with the hardened part, my guess would be around 0,30%-0,40% carbon content. This might seems very low for blade making, but it is the experience that counts for me, and I have been able to get some reasonable Hamons out of it.

Since I want to get more serious I have been trying to get better steel. I can get O-2 steel here, but getting old car springs (I think they're 1095 for coils and 5160 for leaf) would be much cheaper, so I will try these first

For blade coating I have been using 2/3part fireclay and 1/3part powdered charcoal. I then mix it with water till I get the viscosity to my liking.
However, I am planning to experiment using refractory mortar, since I hear a lot of people using this with great success.

As for the oil; Can I just use cooking oil like sunflower- or other vegetable oil?

Thanks for all the replies,
Louis

[CTBlacksmith]

You can use whatever oil you prefer. I use motor oil simply because it is what i have on hand. You can certainly use vegetable or sunflower oil and it will be much cleaner than the motor oil. I have been meaning to go to a fast food or Chinese food place and ask if i can take some of their used cooking oil.

[Steve Sells]

If you really want to learn more, try reading in the blade section of this forum for many posts on this, including blade steels, and heat treating of blades.

[doc]

I'd try canola oil. It's easily available at the grocery store and when we used it here in a class with Don Fogg at Peters Valley it's harding qualities riviled those of water.

Doc

[30cal_Fun]

Sounds great! I learned a lot from reading other threads as well.
But I was wondering: Will using oil for differential hardening make the Hamon less visible?, will it look differently? or will it be just as bright?

Louis

[Max and Kate]

I also heard about using sand to treat the metal but why I don't really know, just bury the blade in sand to cool it. Has anyone heard of this method? I suppose it depends on the type of steel used.

[Frank Turley]

There is a lot of "good ol' boy horse hockey" about heat treatment. I would say that burying in sand is one of those things. I met a couple of old horseshoers who buried their pritchel ends in dirt. Another crock.

Agitating means to move the hot steel rapidly under the quenchant to remove the steam vapor and to allow fresh quenchant to hit the metal. The vapor acts as a brief insulator, and on many tools, it is desirable to get rid of it by agitation. Sometimes, the quenchant is stirred up before quenching for the same reason.

I did a little homework. In "The Craft of the Japanese Sword" by Kapp & Yoshihara, the bladesmith, Yoshindo, quenches the blade in tap water. The average temperature of tap water is 54ºF. The authors say that water at 40ºC (104ºF) begins to retard the hamon formation. I haven't done any personal temperature measurements, but I understand that most folks cannot stand skin contact with a temperature of 150ºF and above. Therefore, I'm sticking to what I said earlier on this thread, that tepid water would be OK, as Yataiki demonstrated. The water was warmed to tepid before quenching, but not enough to retard the hamon formation.

Yoshindo also tempers the blade in the hot charcoal after hardening by heating to 160ºC (320ºF). I am not at all sure how he controls this, because if you think of the "heat rainbow" for tempering, the first surface color seen upon heating is pale straw (428ºF). Yoshindo can temper more than once taking care not to overheat, as overheating might ruin the hamon.

Getting away from blades for a moment, a thicker high carbon tool is often quenched in water, sometimes brine, and both quenchants are kept below 60ºF. If the tool has a complicated shape, oil may be called for.

Quenching oil may be available from McMaster-Carr [?]. Quenching oil is a petroleum product which is created to have a high flash point, less chance of it catching on fire. It also abstracts heat from the hot material at the proper rate. In my small shop situation, I use Quenchtex A, a Texaco product, but I had to buy 55 gallons from a distributor. Fortunately, I was able to sell most of it in order to regain some of the cost.

References:
> "The Craft of the Japanese Sword" by Kapp & Yoshihara, Kodansha, 1987.
> "Heat Treatment and Properties of Iron and Steel" by Digges et al., National Bureau of Standards Monograph 88, 1966.
> "Metals for Engineering Craftsmen" Rural Industries Bureau, London, 1964.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[MattBower]

Frank is giving you good advice, but let me recommend that you do some serious reading on the bladesmithing forums (here and at other sites -- there are some outstanding ones out there). The nature of your questions suggests you don't have much background in this, and frankly no one's going to take the time to fill in all the background info you need in order to completely understand the answers to your direct questions.

Quenchant choice first and foremost depends on the steel you're using. I don't off the top of my head know any bladesmiths who use water for quenching anything other than 10XX and W-series steels. Even with those, water hardening is riskier; you'll lose more blades, though people who really know what they're doing do seem to have pretty good success with water on the 10XX and W- steel. I don't think I know of anyone who quenches 5160, O1, or other deeper hardening in water. (I've heard of using water for heavier cross sections of deep hardening steels, but I'm just talking about blades.) 5160 is designed to be fairly deep hardening; there's no reason you'd need to water quench it, especially in blade cross-sections. Doing so vastly increases your chances of quench cracks, and I know of no advantage.

5160 also is not a steel you'd choose if you're looking for a nice hamon. It is too deep hardening. The martensite will creep up under the clay lines and wash out the visual effect to a certain extent. People do manage to get hamons with 5160, but they're nothing like the ones you can get get from shallower hardening steels.

Not all oils are created equal for quenching. Some are fast, some are slow, some are in the middle. Ideally you'd like to marry your choice of oil to the steel you're using: fast oils for shallow hardening steels, slower oils for deep hardening steels, medium oils for medium steels. Fast commercial oils include Park/Heathbath 50 and Houghto-Quench K. Warm canola is also quite fast. Some folks get pretty spectatular hamons in shallow hardening steels using these fast quenchants. You can quench some deeper hardening steels in these fast oils, but it's probably a little risky. McMaster-Carr's 11 second oil is roughly a medium hardening oil. So are Brownell's Tough-Quench (Houghto-Quench G) and Park AAA. McMaster's 28 second oil is fairly slow. The medium oils would probably do great for 5160 and most of your other deeper hardening steels. They might not be quite fast enough for 10XX and W-series steels, but if you Google you can probably find some specific discussions on that. I don't think I'd bother with the slower stuff like Mcmaster's 28 second oil for blades. It would probably harden a lot of the deeper hardening stuff -- I suspect one reason 5160 has been so popular with bladesmiths for so long is that it's sufficiently deep hardening that you can quench it in all kinds of junk and still get a decent result. But it might be too slow for some, and it certainly would be too slow for the shallower hardening steels.

As for your many junkyard oil concoctions -- your guess is as good as mine.

[Edited for rotten grammar!]

[30cal_Fun]

Frank and Matt,

I appreciate you both taking the time to answer my questions. I know there is a lot of knowledge around and is just waiting to be read, but I just wanted a starter on oil quenching. I have read a lot of posts here and on other forums about water and oil quenching, but I have always used water so far, and I know the Japanese have done so and are still doing so with great success, so all the things I read where confusing me as to which extent water could, and oil should, be used for hardening.

In the two posts above there is for now all the information I wanted of the whole oil vs. water thing. And like you both explained; the rest is up to me to fill in all the background info.

Thanks for all the tips and info, I have a good picture now about how to go at oil quenching. I have found some coil springs, which should be 1095 of the likes, and with some luck I will have a lot of leaf springs too in a week or so. The coming time I am just going to experiment a whole lot with quenching these steel and work from there.

Louis

[MattBower]

A couple extra points about water quenching.

(1) Don Fogg has an excellent discussion here by Randal Graham, who apparently can successfully water quench just about anything.

(2) A thin clay coat very likely increases the speed of the quench (counterintuitive, I know), but also probably makes it somewhat less severe than water on bare steel in terms of uneven cooling and risk of cracks. In other words, the clay coat may actually help improve survivability in a water quench. I always thought it seemed really odd that the Japanese apply the clay coat even on the edge they want to harden; seemed to me like it'd insulate the edge and reduce hardening. Apparently, though, it may have just the opposite effect.

BTW, where'd you get your coil springs? The auto coil springs I've had analyzed were 5160.

[30cal_Fun]

Hi Matt,

(1) I have that one saved, it was a good read but this is also one of the articles that got me confused in the first place.

(2) Nope, not counterintuitive at all. I do know a lot about these kind of things, and your right. The purpose of the thin clay layer is twofold: it makes a bigger surface for the water to contact so that the heat transfer of the steel to the water is quicker, thus improving hardening. And the clay makes for a less abrupt change from water to steel, so that the steel does not contact the water directly. The results: less chance of cracking, more controllable and improved hardening.

The coil springs are from a car, does that mean they're 5160? as far as I know car coil springs are usually 1095.

Louis

[Frank Turley]

You're really guessing at tomcats, if you think junkyard coil springs are 1095. I recommend that you go to www.anvilfire.com. Use NAVIGATE MENU and go to FAQs; then scroll to Junkyard Steel and read. One reason NOT to use junkyard steel; you don't know what you have. Another reason is that if you make and sell a knife and the guy likes it, he may come back three years later and want one just like it. Unless you've kept job cards, you won't have a clue. Many, but not all auto springs from 15 years ago and more, were 5160. As an example, I will give you a list of spring steels from the 1966 Forging Industry Handbook, Cleveland, Ohio: AISI/SAE numbers 5155; 5160; 6150; 9254; 9255; 9260; 51-B-60; 1050; 4161. And that was in 1966!

I am not a superb bladesmith, but I have made servicable knives of W1 drill rod. It has about 0.95% to 1% carbon and comes in 3' lengths which are easy to ship. I get mine from Travers Tool which has an online catalog. Other suppliers are McMaster-Carr and MSC. Using a known steel should give uniform results.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

[MattBower]

Frank's absolutely right. When it comes to scrap steel there is no "usually." Not in the sense that you can reliably know what sort of steel you have just by the type of item you have. I've had a dozen or so scrap steels tested with a spectrometer, mainly to prove the point that these scrap steel charts and the like don't necessarily correspond to reality. For example, demolition hammer bits? The charts will tell you S- series steel. Hah! The one I had tested was 1045. I've had two large auto coil springs tested, and both were basically 5160 (though one had some vanadium). But that doesn't mean your coil springs are 5160. I've not heard of 1095 being used in coil springs as a routine thing, though.

[30cal_Fun]

I stand corrected.
I knew that (coil) springs where and are made from various materials, but I didn't know that it could be this many.
However, the steels you both mention and the steels that are on Anvilfires website all have enough carbon to be hardened successfully. Besides, but correct me if I am wrong on this one, spring steel in general should have enough carbon to be properly hardened.
So whether it is 5160 or even 1095, with experimentation I think I can figure out what hardening method and temperatures work for this steel.

I am buying an old trailer, a small one with a loading area of about 1x1,5 meter, It has some good leaf springs on it that are both about 8 stacks thick. I am going to use the leaf springs as blade making material. I can't find much information about leaf springs though.
As far as I know in leaf springs; 5160 is the most common. Is this correct or are other steels also used often for leaf springs? If you can give me a few options of what I could be dealing with, I would be grateful.

Louis

[Mainely,Bob]

I am buying an old trailer, a small one with a loading area of about 1x1,5 meter, It has some good leaf springs on it that are both about 8 stacks thick. I am going to use the leaf springs as blade making material. I can't find much information about leaf springs though.
As far as I know in leaf springs; 5160 is the most common. Is this correct or are other steels also used often for leaf springs? If you can give me a few options of what I could be dealing with, I would be grateful.

Louis

[30cal_Fun]

I think I made it sound better and easier than it is.

First of all, here are some pictures of the trailer. trailer.bmptrailer 2.bmp As you can see, the structure itself is badly rusted, and restoring it would cost more than buying a new one. But the owner send me extra pictures of the springs, and except for some surface rust, they are fine.
Second, there is no "spring shop" around the corner here. And IF you can find it, it is either already under a car, or you pay 30 Dollars for 50cm (20 inches) of steel, you don't even have to try getting leftovers.
I went to the only scrapyard in the area last Thursday, there were some underneath a boxcar, but they didn't want to take apart the whole car just so I could get the springs.
Living in a country where you can get things brand new is nice, except when you are trying to get leftovers from factories, scrap steel or other stuff thats almost unaffordable when bought new. In these kind of situations, it would be much easier in the USA.

Louis

[MattBower]

Yes, I've often said that, as a rule of thumb, a steel that'll make a good spring will probably also make a decent blade. But it may take some experimentation.

Leaf springs do have a reputation for being 5160. I took a set from the dumpster at my local spring shop (with permission) and had a piece analyzed. It actually was 5160. But that doesn't guarantee anything. I really can't say what other steels might be used even in the U.S., let alone in another country!

[30cal_Fun]

Leaf springs do have a reputation for being 5160.

Oke, thanks, that's what I wanted to know.

Louis

[30cal_Fun]

About the oil mix,
The oils you mention earlier I have not seen anywhere here. But then again, we don't have stores like Brownell's here.
I have a couple of liters of sunflower oil at hand. Someone on another forum said to use a mix of 50% sunflower oil and 50% mineral oil. Why the mineral oil? or would simple sunflower oil be fine?
I have seen different grades of viscosity, I think this goes for mineral oils as well. would it be better to use to use an oil with a low (like 5W-30) or high (like 15W-50) viscosity, or doesn't viscosity matter with mineral oil? Or would it be better to use mineral oil entirely?

Here I go with all my questions again But the whole mineral oil / viscosity thing got me thinking now.

Louis