Caught a 'trailer' on a RFD channel horse show. It showed a blacksmith, (Dave Kramer) making a 'bow pin' out of 1/4" round stock. A bow pin is used to hold the bow on an oxen yoke up in place. More or less a heavy clip like sometimes used to hold pins in cheap clevis'. The quench gave the mild steel pin springyness so it kepts its shape. . . . Recipe. . .(soap solution quench)
5 gal water
5 lbs salt
32 oz Dawn Dishwashing Liquid (blue)
8 oz Shaklee Basic 'I' wettting agent. . . . . .Quench at 1550 F, (light red) . . . . .Expect a Rockweld 43 to 45C, on 1018 mild steel.
Gday Charles, I made this one up. The Shaklee Basic, is a rinse aid for the dishwasher (not you or the wife...;-) I just got the homebrand rinse aid instead. It seems to work great.
I remember seeing an explaination of what each does, but can't remember where I saw it. sorry. If I find it I'll post it for you.
I use detergent on the farm as wetting agent when spraying.
Why in the world would anyone use lye as a quenchant? That's a new one on me. Sodium carbonate (washing soda) in solution has about the same chemical properties but isn't caustic. Did people really use lye?
BTW there are a few minor but potentially important errors on that page. Fryer oil is almost always soybean oil and not peanut oil. Chinese cooks make great use of coconut oil in addition to peanut oil (I get mine from a chinese food wholesaler) so you gotta be careful. Stuff like that.
One thing I'm not sure about. It mentions adding Vitamin E to oil to preserve its life. The life extension chemical we use in restaurants contains Vitamin C. The MSDS says that it's in there primary to induce foaming which helps the primary ingredient (pumice) contact and trap the polymer chains that cause the gelatinous crud in fryer oil.
The best thing that one can do to extend the life of veggie oil is to occasionally heat it to about 300-350 degrees to drive out all the moisture. This stops rancidity in its tracks. I have a small vat of fryer oil that is >10 years old and is still rancid-free. I have an air-tight lid that fits the vat that keeps air and moisture out when the vat is not being used. My use pattern could be called "infrequent", as I currently 'smith only when needed for other work.
One other comment. Turbine oil as is used in steam turbines is practically non-flammable and fairly inexpensive. It was totally inflammable before the PCB hysteria. It is about the same viscosity as ATF and so should make a good quenchant. John
-- John De Armond See my website for my current email address
I suspect the lye was a 'reducer'. Hot oxides abound on metal out of a fire or oven - the lye likely steals the oxide or the Oxygen and reduces the oxides back to metal or flakes it off.
Mart> Why in the world would anyone use lye as a quenchant? That's a new one on me. Sodium
All those chemicals are in there to speed the quench process, ie: cool the metal faster. Water is about the fastest thing there is in the quneching world, but when it forms steam at the interface between itself and the part, the cooling rate is negatively affected. So, the addition of chemicals which inhibit the steaming can help.
Google "ttt curve" (time/temperature/transformation curve) to see graphs of how different steels react to differing cooling rates. The point is that for plain carbon tool steels, the faster you quench (from the transformation temp down below 800 or so degrees F), the harder it gets, up to its max hardness. If you want more, google as follows: +"super quench" +"rob gunter" You'll get about 2 dozen hits. Look at several of them to get both sides of the issue. In case you miss it, super quenching won't do you much good for things that are going to get hot, like power hammer dies, chisels for hot work, etc..
In general, oil is a slower quench than water. Plain carbon steels need the water quench to get fully hard except for VERY small sections. But sometimes you will see plain carbon steels oil quenched to minimize distortion and cracking. This, however, limits the final hardness of the part.
The salt makes the water able to hold a lot more heat and thus have a higher temperature before boiling off.
If you cook pasta, one fills a pot and add some salt. The salt makes the water 230 or so degrees F at boiling and not 210. More salt and the temp rises. See what the temp for molten salt is - that is the max.
The soap is a water wetter and makes it conform to smaller places on the object to cool.
Martin
Mart> So what's to stop you quenching in pure detergent? I mean the super
We used to boil our pasta in water and salt the pasta later. We now salt the water, I just thought it was for flavour. You learn something new everyday :-)
So we have the salt added to increase the boiling point of the water(which in effect would reduce steam), and detergent also reducing steam. The water allows rapid cooling.
Why not use a liquid that doesn't produce steam at all, and still allows rapid cooling?
I suspect that the super quench wouldn't be very effective with high carbon steels, where the addition of carbon of benefit.
So are the limits of super quench for water hardening steels and mild steel?
Would replacing the water with motor oil, in the super quench recipe, be of benefit, or work for that matter?
Regards Charles
Mart> The salt makes the water able to hold a lot more heat and thus
The boiling point elevation from the salt is so slight that it doesn't make any difference. I'm not sure what function the brine actually performs. Perhaps salt crystals plate out on the hot metal and help form steam bubble nucleation sites or something. Salt water is more dense than pure water so the static head down in the tank would be a bit higher and THIS will raise the boiling point a bit. Or maybe the salt is in the formula because brine's always been used :-)
Because the latent heat of vaporization of a liquid is many times it specific heat. It takes one BTU to raise the temperature of a pound of water 1 deg F but it takes
970 BTU to vaporize that same pound of water. If we take water from 70 deg to
212 degrees then we input 142 BTU. To convert that pound of water at 212 deg into a pound of steam at 212 requires 970 BTU.
This holds true for any substance that has a liquid phase. Water has one of the highest latent heat of vaporization of any common liquid so it's an ideal coolant in addition to being common and cheap.
The problem is to get the heat to the water. The film of steam that forms on very hot metal is a very poor conductor of heat so once the steam film forms, heat transfer slows dramatically. These various chemicals are evidently designed to help the water stay in contact with the hot metal and reduce film boiling.
The effect is small, if any, as evidenced by the steel cooling about as fast without them. The major effect will be in the low temperature region where the steel is still hot enough to boil the water but not hot enough to form a resilient steam film.
No, no benefit. Oil has almost no surface tension to begin with so a wetting agent isn't needed. It also has a very high (relative to water) boiling temperature so no boiling point elevation is necessary.
The main difference between oil and water, and the reason oil is slower, is that both it's specific heat (btu per degree rise) and its latent heat of vaporization (btu necessary to boil it) are much lower than water. I don't have numbers handy but as a general rule, oil has from about a third to a quarter the specific heat of water. The latent heat difference is probably in the same range.
If you want a really fast quench, much faster than water, then try a liquid metal. If chemophobia doesn't paralyze ya, mercury would be lightning fast. If you can't get past that mercuriphobia then one of the very low melting point alloys would work. Say, Wood's metal. One of the varieties will melt in your hand. Of course, the price of a few gallons of Wood's metal will make your wallet shrivel up and float away :-)
It might be interesting to see how one of the low melting point solders would work. Something that melts in the 300 deg range.
John
-- John De Armond See my website for my current email address
An earlier poster on this topic said something about trying super quench with high carbon steel and see what happens, but wear safety glasses, etc. What he meant by that was that the higher carbon steels are very likely to crack, maybe with disasterous results. The super quench, from my experience, would be toooo effective, especially if the parts had any rapid changes in cross section.
On last (for me) comment on the utility of salt in the quench: I read, some time ago, that the reason for adding salt (a LOT of salt) to the quench water is that it DOES speed up the cooling rate, but only over a narrow range of temperature, right in the upper end of the transformation range, then it is actually slower from there on down. So, you have to know the shape of the TTT curve for the job at hand and then test the system to make sure it works anyway.
George Dixon, a well known blacksmith from Swannanoa, NC who taught many of us tool making, showed us how to harden one of his favorite tool steels, S1, with salt water, even though it is listed as an oil quneching steel in "the book". The reason for doing this is to take advantage of S1's somewhat strange TTT curve. By doing this, we get a few extra points Rc in the body while actually over hardening the cutting edge of chisels designed to be used hot and cold. Sometimes, that chisel edge breaks off in first use, but grinding it back a bit gets past the VERY brittle edge and to the point where it works, hot or cold, for a long, long time. I say all this just to point out that you can start with the theory, but you need to check things out in practice and adjust as needed to get a useful end result.
Anybody still around here with a copy of Dell K. Allen's "Metallurgy Theory and Practice"?
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54c (but with $3.99 shipping) is it too much? ;)
Page 205, Fig.7-26A shows the salt cystals formed (NaOH or NaCl) at first plunge.
It's been said that when "water" is mentioned that they really mean "brine" or something based on water since pure water is such a crummy quenchant. ??
Anyway...
MT&P page 203 to 204... "The salt addition materially decreases the duration of the vapor film stage. It has been shown that crystals of salt are precipitated momentarily on the steel surface and then explosively thrown off during the intial stages of brine quenching. (Fig.7-26A) [real nice photo of that action on page 205 along with oil's reaction in photo Fig.7-26B] This causes a continuous disruption of the vapor film with improved wetting of the steel and increased heat removal. Brine quenching, because of its vigorous action, removes heat treat scale from specimens much more readily than when a water quench is used."
Pure water can leave soft spots in plain carbon steel because of the bubbles formed and so is seldom used by those that know what they are doing. ;) So naturally I've BTDT! :/
A little Mo or Cr or a little extra Mn can fix that. A little W or V -by themselves- can make it worse.
Also I've gotten better results from quenching oil, made for the purpose, for (thin) knife blades (even when quenching 1095) than I got from pure water or brine. Less warping for one. My blades and springs have been hardness tested and are right on the money too, according to the tables and graphs for each type of steel. So why not use "real" quenching oil in that case? :) YMMV
"A 3-5 percent sodium hydroxide quenching bath has also been found to be a good medium for [straight] carbon steels. This bath cools even faster than the sodium chloride bath; however, more caution must be exercised..."
"Table 7-5 Quenching severity for common media with various degrees of agitation. Still water is 1.0."
BTW, on the metallurgy newsgroup no one has ever come up with a better metallurgy book than Allen's 1969 MT&P for teaching yourself metallurgy. :)
The few books that were mentioned I didn't already own I found at the UofA's library. Funny how a couple suggested were just plain crap. ;) My metallurgy class text is crap too (Neely/Bertone).
I'll buy your copy of MT&P if you don't like it. :)
Cool stuff there John. :) And Pete's stuff too. :)
Hg is mentioned for quenching carbon steel taps, in Brownell's Gunsmith Kinks books "to make them harder than factory". Not sure of the real-world benefits tho.
Cool idea but at those sorts of expenses, O1, 4340 or other alloyed steels would be cheaper and better both?
Using scrap/unknowns is about cheap, I understand "cheap". ;)
There is some new stuff (that I don't know anything about) called "polymer quenchants".
Alvin in AZ ps- Pine for email, Tin & Pico for NGs and SSH to access both :) pps- Ubuntu is perfect for this dumb ol'doze-hatin' Dos 3.3 guy :)
Some metals are water - require a fast fixing. Some metals are oil - require a slower fixing. Some exotic metals are in exotic quenches and might have half a dozen dips in and out of the bath or a certain short time... Shell work not total.
I suspect there are masters that can do multiple zonal using all sorts of exotic tricks of cooling and re-heating.
Water happens to be one of the very best liquids that absorb heat. Exotic chemicals HydroFloro types are like water but are like gold.
Hey, that was a pretty good SWAG on my part, huh? :-) I'm just an amateur, neophyte, beginning noob 'smith but I'm also a retired engineer with many years of utility (translate: steam) experience. I was thinking out loud from a thermodynamics and high pressure steam perspective.
Hmm. NaOH in solution is fairly quickly neutralized to sodium carbonate by the CO2 in the air. That's a problem even for concentrated solutions. I was one of the engineers who designed the first production line for the Combos stuffed pretzel snack product. The pretzels are given their color and outer skin by being immersed in a bath of boiling concentrated lye. Yum! CO2 neutralization was a persistent problem until we inerted the space over the bath with nitrogen.
I suspect that the NaOH/NaCOH bath is faster than NaCl because the crystals are softer but more dense, helping hold water tighter to the metal. Just my SWAG.
I thought I had a scanned copy of MT&P on my computer but I can't seem to find it. Oh well.
Take a look at "Metallurgy of Steel for Bladesmiths & Others Who Heat Treat and Forge Steel" John D. Verhoeven, Emeritus Professor, Iowa State University. It looks very good to me. He addresses quenchants starting on page 125 including polymer quenchant.
This book may not be quit up to Allen's standard but it has one very important feature - Prof Vernhoeven released it to the public domain. I don't recall where I got my copy but I'm hosting it on my Literature and Ebook page on my website:
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Eight mb PDF.
I have a superb old metallurgy book published by Combustion Engineering. Oriented toward boiler steel metallurgy, of course, but it's still an excellent text. In my Round Tuit pile of books to scan.
John
-- John De Armond See my website for my current email address
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