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Hi ya Leonardo.

 

To pick the pepper out of the rat turd, so to speak, I'll tell you what we do in aerospace.

Lower bainite cannot, by spec, be identified by metalographs alone. It must go through a scanning electron microscope to accurately differentiate it from martensite. They are so close in structure.

 

Just a little insight. No steel politics intended. Jerry

 

EDIT: A tidbit;

there is a ditinct, transitional structure between lower bainite and martensite. I don't know the name off hand, but can find it. I do know it is VERY difficult to achieve, as a matter of fact. Laboratory stuff.

Actually that isn't quite true Jerry - see the attached picture. Late plates of martensite with red needles of bainite. Good quality metallography and specialized etching technique

I met Tom at a local ASM chapter meeting in Philly. As I recall, he was a student and needed something for a senior project. He made the pattern welded knife - then cut it up (seems a real waste). He then wrote the results up and the professor recommended an article for Advanced Materials and Process. Good stuff.

Hey man,

 

I found that vibrating the quench was the quickest, easiest way to agitate. It doesn't take much. in a pinch, we've done it by holding a palm sander on the tube. The results are remarkably effective. I don't think it helps past the vapor phase, but before that, there is a marked difference in the quantity of smoke produced. vitually zero. I would usually try to slow the cooling rate down once it got past that point anyhow, so it was ideal. Truthfully, I wouldn't do it any other way with this type setup. the anti scale compound I used to use would cake on in a normal oil bath, and flake off with a water quench, and the astounding thing was that it would make the compound flake off like it was water quenched when we vibrated it

 

Tai Goo gave me the idea to try it, and there is an ASM article that was floating around touting vibrations as being superior to conventional agitation protocol, but I can't seem to find it.

The idea of using vibrations is an old one. It was originally thought to be Russian and in one of their Journals - mid 1970s. There are some articles in Heat Treating Progress in the past year or so that describe the process. It works by breaking up a stagnant vapor phase. It works very well and in just the way you observed.

Just be carful to keep a lid on it when you aren't using it to keep out moisture. my old rig(6" pipe 3' tall, basically a gas forge around a tube) ended up getting a significant amount of waterin it, even with a (loose fitting)lid. OIl float on water, and water has a lower boiling point, and really likes to expand when it turns into a gas, so one day while I was heating it up, the water at the bottom started boiling, making my quench tank into makeshift oil cannon/volcano that shot hot oil everywhere, got on the insulation, caught fire and wouldn't go out. I emptied my extinguisher on it to no avail.

 

Now, I would marquench/temper in it, so the temps were pretty high, but still......

I am glad you weren't hurt. Water in oil is DANGEROUS. Any water greater than 0.1% (1000 ppm) is asking for just the thing that Jesse experienced. In addition - water at lower levels can cause spotty hardness, soft spots and cracking.

The Saginaw Steering Plant lost nearly 1/3 of its plant because of 1 gallon of water in a 1000 gallon quench tank. BE VERY VERY CAREFUL!

I think that quenching 1.05%C steel in water is asking for cracking. As a general rule, steels with a carbon equivalent greater than 0.52 are prone to cracking unless special precautions are taken.

What oil did you quench in? I would recommend a very fast oil - but even then the risk is large that the part will crack.

Well, I didn't take a spoonfull. It was just a very small bit of dust from the "salt".

if it were cyanide - it would have killed you.....

Thanks, Scott. I feel like a bit less of an idiot now. Having said that, isn't the autoignition temperature the really key one, in terms of safety? (If I understand correctly, flash point indicates a bit of a flare-up while autoignition equals major eruption.) I ask this because while the flash point of WD-40 is quite low, the autoignition temp isn't too bad.

The flash temperature is what keeps you out of trouble. As a general rule, don't let the maximum temperature exceed 100F below the flash. You will always be safe.

The best way to achieve that, is to maintain the "one pound of parts one gallon of quenchant" rule of thumb.

Thanks Doc.

 

I tried some more techniques, like masking the blade where I did not want extra carbon and packing the whole vessal. I just didn't want to ramble on.

 

I love 4340. I thinks it's the best low alloy, carbon steel, but a little light on the carbon. This technique should make it useful for cutlery.

 

Don't forget to use this during hardening also. Keeps the decarb down and some of the carburized area will diffuse a bit. Don't worry about insulating the edge from the quenchant. 4340 is almost air hardening. It was born to make martensite.

 

Thanks for the tips. How nasty is the stuff with barium in it? The MSDS looks pretty scary.

Very nasty - don't do it, unless you want your yard classified as a superfund site

Is that why when you full quench in oil you get forward curve, but when you edge quench in oil you still get backward curve?

Well - standard metallurgist answer - it depends. By edge quenching, you get the edge to transform properly. It also depends on the speed of the oil. If it is slow oil, you would have a more uniform quench - and likely would transform the edge to martensite - maybe - and the thicker parts might get transformed to martensite. The steel used may have adequate hardenability to transform completely to martensite. The idea is to have a sharp edge of martensite, and the backing edge of pearlite. If all martensite, the thicker part would expand last, and force it to expand last - causing a forward curve.

That is why a low hardenability steel is used - to force the edge to martensite and the back portion to pearlite.

I recently got some Hydrodur GF made by Durferrit, it's a salt-like powder wich you have to dissolve in water.

 

I have tried it once on a couple of W2 blades and it worked. I put in more then the reccomended 5% so I think it was still a bit slow. This stuff needs more experiments but it looks promising!

 

Oh, and it tastes awfully salt (had to try!).

Check the MSDS. I would be willing to bet that it is a fluoride type salt. It works by breaking up the vapor phase. I wouldn't try tasting salts on a rountine basis. For instance, some of the high temperature salts from Dufferrit contain cyanide. IT WILL KILL YOU!

Anybody ever try WD-40?

 

It's about the same viscosity as Parks 50.

 

RK

Check the flash temperature - it is VERY LOW. It would be dangerous to try that!

Diesel fuel can be used as a quenchant. Gasoline (petrol) cannot. You can toss lit matches into either #1 or #2 diesel fuel all day long without setting it afire. It will catch fire if you get it hot enough, but it takes more than one blade (unless your quench is really too small anyway).

 

The same speed as water, without sori, can be obtained by using water soluble polymer solution with water. It also eliminates the danger of cracking, and is replacing oil in industry here, due to easier cleanup, mostly. I do not know if anyone in the UK sells it, but I have used PEO (polyethyloxazoline) mfd. by Houghton Intl. with great success to produce very cool hamon. It does not produce much sori, and what sori it does make will relax upon tempering in my experience (which I still cannot explain). I would think that PEG (polyethylene glycol) would produce similar results, and it is more widely available here.

 

I have heard it postulated that Park #50 is nothing more than kerosene, though I do not know that to be true or false, having never fooled with it myself. I have quenched in diesel, vegetable oils, and commercial quenching oils, but not that one. I was not trying to produce hamon at the time, however.

For polymers - try Houghton PLC in the UK.

The Park #50 is a mineral oil of very low viscosity. It also has a low flash point.

I would not recommend using kerosene - much too low of a flash temperature. Use a quality quenchant so you can get repeatable results.

Houghton K is THE fastest quenchant out there. It is a premium quench oil. But I am biased

John,

 

If you click the link in my post above, then "Locations" at the top of the page, then "North America" and scroll down, there are tele. #'s and addresses. I contacted Houghton about what I wanted, was then contacted by a sales rep., placed the order, then needed to contact to set up account/payment at a different number. Sounds like a run-around process but it was actually very easy to do... on the money call, I just told them I wanted to pay with a debit card.

 

Houghton sells in small quantity only out of one distribution point and that is somewhere in Penn... I'm not remembering where but I think it was Valley Forge.

 

Mike

It was probably out of Allentown, PA. The Corporate offices are in Valley Forge (where my office is). The main number is 610-666-4000. Ask for customer service. Unfortunately, there is a large up-charge on pails. if you PM me with your location, I can probably find a distributor near you.

Alternatively, you can try Brownnells (it is already pailed off). Or you can try contacting a local heat treater. They probably have a gallon of oil that you can buy from them....if you bring your own pail....

Chris,

 

Do you use this oil and have you gotten any other info on it from McMaster-Carr or the supplier of it (from the MSDS sheet) http://www.motoroilinc.com/? I'm asking because years ago when I looked at these oils I couldn't get info from either McMaster-Carr or Motor Oil, Inc. and I'd love to have the data.

 

It would be lovely if Scott McKenzie saw this thread and were to have some information on these oils.

 

Mike

I have no idea. I have not run into them on an industrial basis. However, if you need a small quantity of quality quench oil - I would suggest Brownells.... http://www.brownells.com/aspx/NS/store/pro...&st=&s=

I know this oil - it is a high quality premium quench oil.

Let me clear up a misunderstanding. The purpose of martempering or marquenching is designed to minimize distortion. It allows the inside temperatures to catch up to the outside temperatures so it transforms to martensite uniformly and at the same time. In this case, the back of the blade and the edge contracted uniformly, but because of the larger mass on the back, the blade bent forward. Both sides grew, but because of the larger mass of the back of the blade it bent because of the shape of the blade. To get a sori you need to quench it to room temperature so the edge cools first and you get differential cooling from the edge to the back.

Nicely done Jerry... You did something called pack carburizing. You can also do something similar with charcoal, cast iron chips, a bit of carbonate. You can also add various stop off compounds - Avion and Condursal are two good ones. They won't spall during carburizing.

Now regarding the etchant, I would suggest nital (2% nitric acid in methanol) - it will show the carburized case if not tempered as white, and the non martensitic areas as a deep gray. Only need about 10 seconds or so, then wash with water. You might also want to use a clamp when polishing so you maintain a sharp edge....

Your estimate of the case depth followed nicely the time at temperature...nice when the science and applied work out together....

Water vapor is very decarburizing because it releases hydrogen and oxygen. The oxygen reacts with the carbon on the surface making CO. That is the reason why you want a low dew point in your atmosphere. That is one reason why people tend to add a small amount of natural gas to the furnace atmosphere - to scavenge the dissociated water....

Lead is still used for wire patenting applications - but they have a real time meeting EPA/OSHA regulations with the stuff.

The "super-quench" would be a fast quench and probably faster than water. The table salt causes the vapor phase to break up faster and initiate nucleate boiling at a higher temperature. The rest is surfactants to cause better wetting of the quenchant on the steel. It would work fine for very low hardenability steels.

Tin could be used, but it may cause liquid metal embrittlement (it depends on the steel composition). Indium and bismuth also cause liquid metal embrittlement. Salts are commonly used for martempering or austempering applications.

Thanks Don

A good rule of thumb is one hour per inch of thickness, 2 hour minimum. The second temper I would do at the same temperature or slightly lower - say 25F. The third temper is the same sort of thing.

Scott,

 

Make video, put it on DVD, and sell it -- along with any accompanying handouts and similar materials. (Or tell the ASM to do so.)

 

I don't know how it works in the heat treating industry, but in my profession that's done all the time for continuing education.

I am not sure if they will - but it would be excellent. I know the quenching forum will be truly hard core technical. It will be a lot of fun!

Here is a thing I found interesting...

 

Part 1

 

Part 2

Mike - those are decent articles by Dan Herring. Interestingly, Dan, and the people that he referenced (George Totten, Jan Bodin, Soren and Gajin), are friends of mine, and all serve on the Quenching and Cooling committee of ASM.

For those that are interested, there will be a course taught in Milwaukee in September on Heat Treating for the Non-Metallurgist. I will be the instructor. There will also be an EXCELLENT symposium on quenching following the course.

Links:

http://www.asminternational.org/heattreatedgears08/

http://www.asminternational.org/heattreatedgears08/edu.htm

The course will be a lot of fun - and you will learn a lot about the basic metallurgy, and how the "big boys" do it. /end of ad

Brian,

 

You might be able to find chemistry for a brand of ATF/brake fluid through MSDS sheets.

 

The canola oil you mention, is it the scavenged "old french fry oil" you described in your first post?

 

Besides Park and Houghton Int. and Chervron (who now owns Texaco and offers at least some of their quenchants), I don't know of other manufacturers. I know MSC has a "fast" and "slow" oil but they obviously don't manufacture it and I've not had any luck with them in finding either how fast/slow it is, or the original manufacturer. There are a number of outfits out there who simply repackage... like my under standing Brownell's "Tough Quench" is rebranded Houghto-quench "G" from Houghton International. My luck getting hard information for rebranded quenchants from their sellers is poor and hearing from a sales rep., "Yeah, that should work for that", isn't particularly informative.

 

Scott,

 

Are there a lot of other manufacturers of quenchants in America besides the three I listed, or manufacturers who sell their quenchants here?

 

Mike

The heat treat industry is very fragmented. But Chevron has ceased production of QuenchTex A and QuenchTex B. They may have stopped production on others too. I would suggest that you contact a local oil distributor. Exxon Mobil produces some, and there are many foreign companies too - like Elf-Fina. They may have a house brand. You are correct about Brownell's. If it were me, and had to quench my work, I would stick to the major players, and ones that will provide some decent information up front. At least a data sheet that describes speed (GMQS), viscosity, and flash point. Cooling curves are also nice, but you have to take them with a grain of salt. There are many different ways to do a cooling curve. It is best if they are compared in the same lab at the same time. GMQS is a decent quantitative method of comparing oils.

Just remember, I may not be able to devote a lot of attention other than the time that I spend here. I am often dealing with orders of 1000 gallons and a lot more - like coordinating a 10,000 gallon order. I will also try and answer everyones email - but I also get about 300 a day from all over the world. It just may take me 24 hours or so.

Scott,

 

Seems to me driving the water off would be running the veg. oil above the local temp. for boiling water. Is there something about this I'm not understanding?

 

Mike

That is correct - but do it slowly by raising the temperature slowly. Hold at 180 for a while - if there are bubbles then hold there til it goes away. Raise it again a bit higher and repeat. Eventually raise to 220 or so and allow to hold. Allow to stop bubbling. then cover, and allow to cool.

Scott, is there any way you could rank the relative quench speed of vegetable oils like olive, canola, and peanut compared to the others on this chart? How about mineral oil, ATF or DOT3 hydraulic brake fluid?

 

 

Thanks,

Brian

Brian:

It would be hard to classify the ATF or brake fluid. If it is assumed that it is a straight mineral oil (and that would be the worst case), then I would expect it to be a slow oil (17-20 GMQS), and similar to machine oil. I would put the vegetable oils close to cottonseed oil. But that is an estimate only. Personally, I really don't like the use of ATF or brake fluid. It contains some additives, such as zinc that is good for lubricity, but is not appropriate for quenching. The use of an oil suited for quenching is best, and will provide the best results. To some extent, this would include the vegetable oils, as long as the water is driven off from the oil.