kb0fhp

OK - I guess I can add my two penies worth.

Attached is the CCT Diagram for 5160. It shows that it takes approximately 75 seconds for the material to cool and completely miss the bainite nose or knee (nose or knee depends where you went to school). The MS temperature is approximately 500 F, or 275C. THis is way too high to use an oil - it will burn up! As an alternative, and what is often done in industry, is to quench the part to a reasonable mar-tempering temperature - say 275 F or 135C, and hold there for a bit of time. Then pull out and air cool. The part is then tempered normally.

Alternatively, industrial practice is to do a "timed-quench", or more properly, and interupted quench. In this case, the part is quenched into a slow oil or polymer quenchant until the desired portion of the part is just below the MS temperature. The part is then removed, and allowed to air cool. Some auto-tempering occurs because of the residual heat - but that is not a big deal. This is common practice in the forging industry, when the parts are huge. It is also applicable to smaller parts.

Either practice will work just fine, and prevent the formation of bainite.

Hope that clarifies things.

Scott

Jen:

The vapor phase is caused by the lack of dirt, salt and other stuff in the water which causes the bubbles to nucleate. If I wanted a long stable vapor phase, I would use simple distilled water. If I wanted a faster quench, I would use a rougher surface, or have a little bit of salt in the water - like normal tap water. Use a lower temperature will make a faster quench.

As I understand it, the goal is to have a fast quench at the edge, and a slower quench opposite the knife edge. This produces the hard martensite at the edge. A more ductile microstructure is desired at the back edge....(I am not sure what you call that part of a knife)... It is these different microstructures that produces the pretty hamon...Using a rougher surface in the clay should produce the faster cooling at the edge.....

Someone correct me if I am wrong....

Scott

the carbon content is .67,not the .067 as posted earlier.

Then it should work fine.....0.067 %C wouldn't have hardened at all....

That is why adding just a small amount of salt makes a big difference in the quench rate - and why agitation is so important.....

i e-mailed the person who did the analysis to double check the percentages. the other question is what do you think of the copper content?

Typical tramp amounts....even in steel scrap that you find or buy nowadays - it is a common tramp element...and the amounts seem a bit high, but not unusual.

Scott

Jen:

I concur with Don. I think that you got a very persistant vapor phase that slowed down the quench. With boiling water, because it has such a stable vapor phase, agitation is extremely important. The purpose of agitation is to wipe the vapor phase from the work so you get proper hardening. I have attached an image that shows the differences between the cooling curves of water and distilled water at various temperatures.

Hope that helps.

Scott

Canola Oil works well.

There are also many quenching oil companies out there - I work for one of them - Houghton International, Valley Forge PA 19482.

Scott

i had an analysis done on a piece of steel and i was wondering what people thought of this metal for knife material. thanks Dan

 

C 0.067

Mn 0.03

P 0.035

S 0.001

Si 0.03

Cu 0.30

Ni 0.01

Cr 0.00

Mo 0.00

Just double checking the carbon content - is it 0.067 or 0.67%? If it is 0.067%C, then it won't harden at all because of the very low carbon content....Just double-check to see that you didn't add another "0" in there.....

Scott

Attached is a paper by Tatsuo INOUE, on the Science of Tatara and Japanese Sword - Traditional Technology viewed from Modern Science, ICBTT 2002. It gives a good explaination from a metallurgist point of view regarding the formation of the sori. I think that this might clarify things a bit.

Scott

International_Conference.pdf

How did you make the ring? I have seen large industrial ring rolling, where they take a billet, pierce it, and expand it while it is rapidly spinning - similar to making a piece of pottery on a pottery wheel...

Vey nice piece of work. I really like the ring.

Scott

A very interesting article .

on page 4 you have a picture of a composit patternwelded swirled blade paterna nd a discription of wootz paterning next to it .is that image soposed to be wootz ?as it is not wootz

Good catch. Actually the caption indicates that it is a Damask Pattern. This picture was obtained from a website of S. Ranganathan, Honorary Professor & Senior Homi Bhabha Fellow, Department of Metallurgy,

Indian Institute of Science, Bangalore 560 012. INDIA.

I have emailed him to verify the source of the picture - whether it is composite pattern welded blade, or something else.

Scott

Jesus:

I loved your website - very excellent. Very nice presentation. I also love the pattern on the knife on your webpage home!

Scott

Attached is the long article on the history of quenching - about 8 pages, with pretty pictures and references.

Let me know what you think.

Scott

The_History_of_Quenching_Revised.pdf

OK - A couple of things that stand out:

The volume in the furnace is approximately 0.25 m3 or about 10 cubic feet. As a general rule, most furnace manufacturers recommend 3-5 volume changes per hour, so the flow rate to the furnace should be 0.75 to 1.15 ubic meters of gas per hour. You indicated 5 Nm3 - this sounds like pressure*volume. Perhaps I misunderstood your units. If no leaks inside the furnace, I would expect a pressure of about 0.1" Hg to 0.5" Hg inside your furnace - this would obviously increase during quenching. The positive pressure inside the furnace is designed to keep oxygen out of the furnace - particularly immediately after quenching, and helps to prevent the outer door from blowing off.

If you don't have the proper positive pressure inside the furnace, you could have trouble with air entrainment, with resulting decarburization.

The en8 grade of steel is similar to AISI 1040 steel. Your carbon potential is too high - I would expect you to have a carbon potential at the furnace of approximately 0.42%C. Although, that makes sense if you are trying to overcome decarburization.

The air/natural gas ratio at the endo generator is WAY off for natural gas. It should be around 3.1:1 air to natural gas. If you are using propane, then the ratio should be about 8:1. You may want to verify that you are using natural gas or propane.

Typical endogas generators produce an atmosphere of approximately 20% carbon monoxide, 0.2% carbon dioxide, 40% hydrogen and 40% nitrogen. I would check to make sure that you are getting the proper mixture. If this mixture is off, even the slightest bit, then your oxygen probe at the generator, and at the furnace would provide completely bogus numbers. If you are using propane, at the prioper air/propane ratio, then the amount of CO would be about 23%, with all other numbers about the same. Checking the atmosphere with a dewpointer, I would expect the exit gas of the generator to be approximately 40F (4C) to prevent sooting in the generator. Using the dewpointer doesn't tell the whole story - you need to know the CO and CO2 ratio to set up the oxygen probe correctly. Use an infrared analyser (Siemens makes some good ones) to verify and set your CO/CO2 ratio.

Lastly - check the furnace tightness. You could be sucking in air from around the heating element terminations through the shell, from the radiant tubes, or around the door seals.

One good practical check between the oxygen probe and the actual carbon content of the furnace atmosphere, is to use some low carbon shim stock. Use thin (2 mm or so - thinner is better) shims and hang off your furnace rack. Allow to soak for about 1-2 hours. Remove the shims and measure the carbon content on a Leco carbon analyser or equivilent. With this thin shim stock, the shims will gain the carbon in the furnace atmosphere, and will give you an excellent measure of the actual carbon potential of the furnace. I used an infrared analyser to get me close, then used shims to get the carbon potential to tweak the carbon potential to be exactly where I wanted it.

Do you see a difference in decarburization from the first load in the week, to the last load of the week? If so, then perhaps there is excess air inside the furnace refractory that is causing the decarburization. In my shop, I always allowed the endothermic atmosphere to "sweeten" the refractory for about 8 hours or so prior to introducing my first load. This allowed the atmosphere to displace any entrained air in the refractory and replace it with endothermic atmosphere.

As a first thing to try, I would check, verify and recheck the endo generator, and make sure that you are getting the proper mixture, and the proper atmospere cracking.

I would also look at the furnace, and make sure it is nice and tight. Once the generator is producing good gas at the proper CO/CO2 ratio, I would make sure the flow is good, and that you have a good solid burnoff of gas at the exit end. When you open the outer door, you should have a substantial flame curtain that reaches above the top of the outer door. This will prevent oxygen from entering the furnace, and prevent blowing the door off immediately after quenching. It should take very little time - no more than a couple of minutes - to establish a proper burnoff at the burnoff pipe. This is important from a safety point of view, but also from a process control standpoint. If this doesn't occur, increase the gas flow until you do have a solid burnoff.

Lastly, I would also try using some shim stock to verify your oxygen probe settings.

I hope that helps. If you have questions, you can email me at work at smackenzie@houghtonintl.com.

Scott

I do not disagree at all, but the one puzzle remains, even if the hypothesis (that it is mechanical, and not metallurgical) is correct. Why does the sori relax upon tempering ?

It is both a mechanical and metallurgical issue. At the edge, the microstructure is martensite, and at the backside, it is predominately pearlite. There is a volume expansion of about 4% due to martensite transformation. This causes some residual stresses. As the martensite tempers, some of the carbides precipitate out, resulting in a relaxation of the stresses, and a change in the volume. Hence the sori relaxes.

Hope that helps.

Scott

Motor oil is not a good quenchant - for a lot of reasons. It contains a lot of nasty stuff in it that is toxic and difficult to dispose of. Second, the cooling curves are poor.

If you use a quality quench oil, the results will be excellent and consistent. Use a medium speed oil, so that the thin sections harden, and the thick sections do not harden....depending on the hardenability of the steel, a fast oil would also work.

I can help you select if you PM me...

Scott

 

I really like the aqueous polymer PEO, but it had it's own set of issues to deal with. But for making hamon, oh Baby is that stuff neat! And it washes up with water too.

Howard - where are you located? Where did you get your PEO - I assume it is Aqua-Quench 3600. What sort of concentration do you use?

Thanks

Scott

The article is attached in the other post.

Thank you for you patience. I just was able to read it after it published tonight. Sorry for the double post.

Scott

It has been my experience, and well documented, that 4340 also suffers from segregation and banding, but due to Cr. It can appear from incomplete homogenization at the mill, inproper rolling temperatures, and also excessive normalization temperatures.

Scott

Ok - I can help with this...

As I understand this, it is a intergral quench type furnace, using endothermic gas, with a dew point of 3F.

What is the size of the furnace (intererior dimensions) - you can also tell me the brand and designation.

What is the endo flow rate into the furnace?

What is the dew point measured at the furnace?

How are you measuring dewpoint?

What is the material being heat treated?

Do you have an oxygen or carbon probe in the furnace? If so - what is the carbon potential of the furnace?

What is the natural gas/air ratio at the endo generator?

What is the alloy and temperature?

How long of a soak time?

This should give me a good start on helping you.

Scott

ASM Advanced Materials and Process just published a short paper I wrote on the history of quenching. The article was cut by approximately 70%. If you can find it on the web (I haven't seen it yet) - let me know what you think. I appreciate all the help everyone provided!

I found the article. You download a copy requires a membership in ASM - which a really recommend. I have attached a copy.

Scott

Quenching_History.pdf

I would be interested in finding out more information - it is not too far from me in Valley Forge. I would love to see how it is done....

Scott

I am going to offer something different.....

The post indicated that the 1045 die was used annealed, and was satisfactory. Even a little bit of hardening would be a bit help increasing the die life.

First I would stress relieve it - 650-700F for a couple of hours. Then I would slowly bring it up to heat to about 1500F and hold for about 1 hour per 25mm thickness (cross section). I would then quench in a fast oil - canola would work, with the oil heated to about 150F. Strong agitation at the beginning, then very little toward the end of the quench. Then temper at a reasonable temperature like 350F to get the maximum hardness.

I would use cast iron chips, with a bit of carbon and calcium carbonate mixed in to provide a protective atmosphere. about an inch on the bottom of the box, then the part, then more cast iron chips piled on top, and then put the box in the furnace. Heat to temperature, take off the lid, then quench.

Remember, he is using the tool at about HRC 20 - anything would be better....

Scott

You have them as PDF? I paid $1000 for mine....I got them as a graduation gift to myself....Cool - download the 58Mb zipped file in less than 1 minute......Thanks!

Yeah, but it is in French. Later this week I will translate the calculation part and send you the *.xls file to be seen with Excel. But the first thing to do is to read the article by Lucke & Detert. Can you have it? If not, I will try to digitalize it for you.

 

I have not found the books you've mentioned in the electronic form. However, I have the full collection of Cahn (3 volumes) as PDF. The link is just below

 

h**p://rapidshare.de/files/21073121/CAHN__R._W.__1996_._Physical_Metallurgy__4th_ed.___3_vols._.rar.html

 

--> copy-paste the link in your web browser-->a new page will open--->click on the Free button at the bottom of the page-->wait a few seconds--->type the words that will appear on the screen and hit OK for download.

 

Cheers,

Maleck

You may want to check out the book Dislocations by Hull - excellent text, and it will help you calculate the break-away forces. Also, look at the expensive 3 volume set of Physical Metallurgy by Cahn et al, and Dislocation THeory by Weerzmann.....I would be real curious to see how you make out. I can help check it if you want....

http://www.scielo.br/scielo.php?pid=S1516-...ipt=sci_arttext

Paper with references on diffusion of Cr in steel as a functon of grain size.....

I don't have any idea if Shewmon had any ebooks - I really doubt it. He was a lousy instructor, but his books were excellent!.....Let me check out my books....

You can use the flux and divide it via the area of interest to get the velocity.....

Hope that helps

Scott