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BossDog
01-03-2011, 08:41 AM
I've seen lot's of photographs of steel structure. How do you do that?

Kevin R. Cashen
01-03-2011, 12:58 PM
It is not as easy at it may seem and I get a lot of makers asking if all they need is the microscope they are looking at buying. I often puzzle them by meeting this question with another, "why on earth do you want a microscope?" Allow me to first explain this. Metallography is a very expensive and time consuming sideline of mine that actually contributes little in a direct way to my making of knives; it certainly won’t save you any time while it eats up all your spare moments. I actually didn’t initially get into metallography to help with my knives but to get answers to questions that I couldn’t get elsewhere about so many of the myths and misconceptions in knifemaking. Instead of relying on trust, faith or assumptions of others about what was happening inside the steel, I asked myself “why not go straight to the source and actually see for myself what is happening inside of the steel?” What I have found has changed the way I approach the craft and make my knives but it actually hasn’t helped to make them in any way, like a power hammer or good grinder could. So unless one is ready to expend a lot of money on a huge time vampire I would go for a new kiln, a new forge or something more practical, but enough of that now on to how cool it can be to seen inside the steel…

Metallography is an art unto itself and a whole subsection of material science. The first consideration is how and where you will be looking based on what you may be looking for. You want a true representation of the internal structure of the steel so most often the best perspective will be perpendicular to the cross section. Just looking at the sides of the blade will tell you almost nothing. So the first thing you will want to do is cross section the steel. The problem is that you want to know you are studying the untouched condition of the steel and must not affect if by the preparation process, so cross sectioning and grinding can be tough since you must generate no heat in the process. Very thin specialized water cooled blades are used to cut the steel, the cheapest are simple abrasives but are VERY fragile and the work must be very rigidly held to avoid blowing up a blade, you can also get more durable diamond blades made specifically for hardened steel but they are incredibly expensive.

Kevin R. Cashen
01-03-2011, 12:59 PM
Anyhow after the piece is cross sectioned and you have a wedge or sliver of material to mount up you are ready to begin preparation. One quick note first- you want the samples as small as possible, for ease of mounting, ease of polishing etc..., I like nothing wider than 1” at its largest dimension, if it is blade shaped and around 10 mm x 10 mm if square. I have a special cabinet I built that holds the resins and moulds for mounting. It has a glass topped vibrating table to work on. The sample is placed in the glass face down and then a mould ring is placed around it. The ring makes all my mounts the exact diameter of the holder on my microscope stage. Next a resin is mixed and poured around the sample and vibrated to remove air bubbles. The bubbles are bad as they leave pits in the front surface that trap abrasives and cross contaminate my polishers (very bad).

The hard resin mounting is important for holding the piece, in polishing, on the microscope and for final storage.

http://www.cashenblades.com/forum/samples.jpg

I have file drawers full of catalogued boxes filled with holes to hold all the 1.25” mounted samples. But the most important reason for the mount is so that you can observe the edges of the sample, without it you would undercut and round the metal edges in polishing and never be able to focus on them with the scope.

After the resin is set, I begin polishing. Polishing starts at 200X, then 400X and 600X (all with water feed) and then I move on to hand lapping on wet paper- 800X, 1500x, 2000X. The mount is then rinsed and I move on to 3000X diamond paste on a leather horizontal power lapping wheel, followed by 8000X and then 14,000X with a thorough rise in xylene or alcohol in between. If the is any cross contamination from one wheel to the next you need trash that wheel and get a new one. I even keep my wheels sealed in a Ziploc inside a cabinet when not in use to keep all dust off from them. Next I go to soft felt wheels to finish at 50,000X or 100,000X grit.

The sample is now put on the scope and examined for defects or scratches; I will most likely be going back to the felt wheels for some touch ups. When all is ready I can now etch.

Kevin R. Cashen
01-03-2011, 01:00 PM
Etching is essential for metallography; just looking at unetched polished steel will only give you a view of total white on white with no details. Every detail you may want to observe will have its own specific etchant you must use to reveal things, and none of them involve ferric chloride. Many make the mistake of thinking they can use FeCl but it will not reveal the microstructure at all under the scope. I mostly use a 2% nital etchant; it is a mixture of pure alcohol and nitric acid.

The sample is rinsed cleaned with denatured alcohol (being careful to rinse more that rub it clean as even a cotton swab will scratch it at this point.) and then immersed in the nital face up. The nital should be slowly agitated so that nothing can settle on the prepared surface. It normally takes from 30 seconds to a minute for the “bloom” to form when you can see the darkening of the sample from the etch occurring.

It is very easy to under-etch or over-etch, and in either case you will lose the details you are looking for, only practice and intuition will help you judge when you nailed it. The sample must then immediately bet rinsed under clean water. I then place it in alcohol to remove any water and have a hot air dryer ready to dry it off as soon as I take it from the alcohol. If liquid is allowed to sit on the surface it will form a film that will ruin the sample, and you CANNOT touch it now with anything but gentle air.

Kevin R. Cashen
01-03-2011, 01:01 PM
If all went well you are now ready to look at the inside of the steel with a microscope. I have several but my favorite is my Olympus PME metallograph. It has very good inverted stage and was made for taking pictures. Inverted stages are good since they view from below and sort of self level the pieces, if you view from above you need to mount the mount on a slide in such a way that insures the sample is absolutely level, so that one half of the view isn’t always out of focus.

I can view from 50X up to 1500X magnification with my PME and use a good cannon Camera on the camera port to take pictures of stuff I feel is important to document. I did use an A95 point and shoot with very good results for years but had to use special adapters to mount it up. I now have an 18mp T2i EOS that mounts directly with a T-ring but the images are so darned detailed I now need to upgrade many of my microscope objective since the camera can exceed their image quality.

On the PME if I want to take a picture I pull a knob below the eyepieces to open the port and send the light down to the lower unit when another knob will enable a prism to send the image to the cameras image sensor. The image is then seen on my 20” LCD computer monitor and I can refocus and arrange the shot and shoot using the remote interface with the computer. This can be important since touching the camera can result in blurred images due to the slightest movement (it is also a good idea to lock the mirror up for shooting).

http://www.cashenblades.com/forum/pme.jpg
Here is an image of my PME using my laptop before I upgraded to the new computer and better monitor.

That is pretty much all of it, but there is one last thing to mention about microscopes- they must be of the reflected light variety. Of course this requires special optical arrangements that send the light through the body of the scope and through the same objective you are observing with. Steel is opaque so a regular microscope that illuminates from below will not work.

J. Doyle
01-03-2011, 03:19 PM
Kevin, I know you've said before that it was a lot of work. But now that you've explained it some........all I can say is WOW. That sounds very tedious and time consuming indeed.

Just want to say thanks for sharing your findings with us when those of us who do not have the time or equipment ask our questions. It's pretty cool that you will share your educated explanations with us so that all of us can try to approach our craft from the best angle possible.

It would be easy enough for you not to care or bother explaining to us, especially when there are many guys who don't care about the best end result. Fortunately, I do not see many of those folks here. Smaller minded people with your equipment and findings would tell us to 'Get lost'.

Kevin R. Cashen
01-03-2011, 05:04 PM
Well, I really need to be honest that I am no saint and altruism is probably not my motivation, but instead I am insanely stubborn and am incapable of backing down from a challenge. Years ago when I decided to do something as radical as to verify some of the things I have been told were beyond question in knifemaking, I was astonished at how upside down the “traditional wisdom” was in just the few areas I had scratched the surface to see. To be honest I felt a bit betrayed by the “experts” to whom I had blindly listened to for so long, and I vowed then and there to give back to this business by sharing as many facts as I could to help others from being victimized by bad information.

I had no idea, however, how emotionally attached, in a very personal way, so many makers were to their beliefs and assumptions and was not prepared for the venom and animosity they could greet any contradictory facts with. Believe it or not there are people in this world who will hate another human being simply for not supporting the way they heat a piece of steel. I guess this was the wrong approach to take with a guy like me because that type of intimidation only raised my determination to a whole new level, and I built a metallurgical lab onto my shop just to provide me with the data I needed to combat the misinformation. Believe me it wasn’t easy, some like to portray me on the wealthy elitist extreme from their poor man’s approach, but I can assure you they no doubt make many more dollars a year than I do. I built my own shop and took 30 years scraping up and assembling what I have. Like so many others, I started out with a ball peen hammer, a chunk of railroad track and an old sink for a forge, but I just never quit learning or improving what I had.

Somewhere along the line changing my profession/craft for the better with solid information became my main goal, and if there were people who would see me as an enemy for that, then so be it that is between them and their creator, and, despite how heavily the loss of their friendship weighs on me, I can’t help them.

But there are so many others who have been as kind and encouraging with their words as you Mr. Doyle and them I can help, and will, whenever possible. The people who violently deny facts to preserve their own world view don’t need to “get lost” since they already are, but on the other hand folks such as yourself don’t need to build a metallurgical lab if I can share whatever knowledge mine produces.

Kevin R. Cashen
01-03-2011, 05:29 PM
More about metallography

In this logo banner are just a couple of the things you can see after following the steps outlined above:

http://hypefreeblades.com/forum/styles/proFormell/theme/images/header_wide.gif

The first image (after the logo) is coarse pearlite that you will find in 1095 if it is heated above critical and cooled very slowly. The next is our necessary friend, austenite, the phase you get when you heat the steel until is glowing red and very soft. Third is or very best friend and the goal of our efforts, martensite, the hardened phase of steel (what happens if you cool the second image fast enough to avoid the first image;). Next is what you get if you have a lot of carbon, overheat it and then cool it, a bit of a troublesome mixture, at very high magnification (over 1000X) . And lastly, an image of steel that doesn't have enough carbon to make martensite or pearlite without big blobs of unused iron (ferrite) left over.

BossDog
01-03-2011, 08:12 PM
wow...I had no idea the surface preparation was so detailed. I am impressed and amazed. Thanks for the recap. You have just shared knowledge (again) that maybe no one else in our industry has or least that I've never seen. Thanks Kevin.

clancy
01-03-2011, 08:19 PM
The sample prep is standard analytical lab work but the difficult thing is interpreting the photos. You can throw a lot of money at getting samples prepared and not understand what it all means.

As for people spouting nonsense, You are 100% right! Last summer I went to the ABS meet in Auburn, Maine. It was very difficult to listen to big name "experts" say things that I know to be wrong. If only they knew a little chemistry!

ernie

Kevin R. Cashen
01-03-2011, 10:09 PM
It is indeed standard, and I only make it sound so Herculean because I have had to build much of my own equipment to do it and improvise ways to accomplish what guys do in no time with the proper tools in labs every day. The aggravating thing to me is the number of characters that have foisted an impressive line on a public that isn't familiar with the process. Like your experience at the ABS hammer-in, I have to bite my tongue all the time when I read and hear well known “experts” say they know their grain size, microstructure or other features from “lab testing” but don’t seem to have access to or know anything about these procedures. Etching and looking at the outside of the blade doesn’t tell one anything many are led to believe. I work hard to get to the truth while others just sort of pull their own truth from thin air, that can be aggravating.

As for the ABS, I used to be a very big critic of much of what they taught, but how they won me over was how they received my information. Instead of shutting me out, shouting me down or going after me, they did a very rare and noble thing, they gave me a platform from which to speak and teach. Many are quick to give lip service to free speech, but how many groups will give a stage to opposing viewpoints? I have taught metallurgy to mastersmiths eager to learn, I have spoken freely at hammer-ins, and the ABS now offers many of my lectures on DVD. I know the group’s history and its faults, as well as the damage to knowledge many of it‘s smiths have done, but the group has my undying respect for how it handled my “heresy”.

clancy/ernie this is not to say that I don’t know exactly what you are talking about, believe me I have dealt with it for years, there are many smiths who hold a rating with the ABS that still need to be reached, and some who won’t be reached, but I welcome their time in the podium as much as mine, so long as there is a level playing field and the people have an opportunity to weigh all the facts and sort reason from hype.

Folks I must apologize for all this preachy talk on my part, but I started the New Year by having to deal with yet another rather vicious personal attack at another web site for simply suggesting that each steel could benefit from its own specific heat treatment for its unique chemistry. As always it effects me and dominates my thoughts even in other conversations, forgive my preoccupation with the trying politics of our business, but as I mentioned earlier, I tend to deal with such things by intensifying my sharing of information and thus this thread was most welcome.

Dan Pierson
01-04-2011, 08:35 AM
Thanks for the details about how you do all this Kevin. I'm sure it's standard prep to those
who understand these things but it's new to many of us.

Now, how did you get a picture of austenite?

Kevin R. Cashen
01-04-2011, 09:33 AM
Thanks for the details about how you do all this Kevin. I'm sure it's standard prep to those
who understand these things but it's new to many of us.

Now, how did you get a picture of austenite?

:biggrin: Great! Somebody asked the question I was hoping for:biggrin:, I am not surprised it was you that caught that Dan!

Indeed how does one micrograph a phase that is only stable above 1335F? Once again there would not be a story if I simply had access to the best labs where they actually have the ability to look at very hot things, but I had to get much more "creative".

I was writing an article for the ABS about austenite an realized that I really needed some images of the phase. Obviously I couldn't go to austenite at 1500F and do all the polishing handling and prep, or have my equipment survive, so I made austenite come to me!

With more and more alloying the stable temperature of austenite gets lower and lower, until you have things like "austenitic stainless steels" which are nonmagnetic at room temperature.

Now this may sound like the problem was solved as soon as I sectioned of a sample of 304, but it was not that easy. The stuff is stainless so nital etchant won't touch it:2:.

I have more than a couple metallography books setting around so I looked up the appropriate etchant for austenite and stainless steel. Remember I mentioned that you needed to choose your etchant according to what you wanted to look at, well there are literally entire books devoted to all the combinations of chemicals to make different etches containing everything from potentially explosive compounds to potentially lethal gasses. In the later half the 20th century a man by the name of Beraha added a whole new level of sophistication to the types of color contrasting etches, so it is really a science unto itself.

I did find one electrolytic recipe for stainless that used items that were both safe and obtainable, but where could I find oxalic acid?? I looked at my wifes rhubarb patch and the mounds of oxalis growing near my house but thought that would be way too much work (don't laugh I once produced a potassium based mix I needed from nettle ashes). Something chewed a the back of my brain that I should go to the lumber yard, and when I was there it clicked... WOOD BLEACH! (pure oxalic acid).

I brought it home, made a solution and then stripped the wires on the end of a little AC/DC adapter I had and voila! I could see austenite with my own eyes for the first time! All these years I could make it and feel it under my hammer I knew it was there but to see it with my own eyes was pretty cool!

Wayne Coe
01-04-2011, 12:03 PM
Thanks, I have seen similar pictures but did not know how they got there. This is information that I will probabaly never use but interesting to be exposed to. Again thanks and you have just convinced me that If I need to know about the interior of the steel I need to check with you and not start trying to do it myself.

Doug Lester
01-04-2011, 02:04 PM
Ya, I know the type. In the health care field they are the one's who go by what their gandmothers, who didn't even finish high school, said over what someone with an M.D. and a passle full of contunuing education credits says. They're the same ones who claim that you can't weld in a gas forge and the only people who do hollow grinds are those who don't know how to use a grinder (little gems that I ran across when I was researching knifesmithing) even though people weld in gas forges all the time and that hollow grinding goes back around a thousand years. It all falls under the heading of you can't cure stupid.

That said, thanks for the info, it explains why its hard to find someone to do this for you and that you'd probably not be able to afford it if you did.

Doug Lester

James Terrio
01-04-2011, 03:18 PM
I'm one of those curious/cantankerous sorts who hears the conventional wisdom and says, "Ok, but why? Can you show me?" Not as a challenge, simply because I really do want to know. It's fascinating stuff! I very much appreciate how much some makers do to encourage reasonable questions and look for real answers. Thank you Kevin!

BossDog
01-04-2011, 06:28 PM
I was wondering how you got that austenite picture but I thought I'd already worn out my welcome..:biggrin:

Mike Carter
01-04-2011, 07:48 PM
What? Do you mean packing the edge of a blade by pounding it under a full moon with the tip pointed north doesn't really make a superior blade?!!!!

Seriously, I too appreciate the information you share and the efforts you put into your research. I never really thought much about the process of what you do but I had no idea it was so complicated.

Sean Cochran
01-04-2011, 08:19 PM
Well, I really need to be honest that I am no saint and altruism is probably not my motivation, but instead I am insanely stubborn and am incapable of backing down from a challenge. Years ago when I decided to do something as radical as to verify some of the things I have been told were beyond question in knifemaking, I was astonished at how upside down the “traditional wisdom” was in just the few areas I had scratched the surface to see. To be honest I felt a bit betrayed by the “experts” to whom I had blindly listened to for so long, and I vowed then and there to give back to this business by sharing as many facts as I could to help others from being victimized by bad information.



Thank you for that.
Please dont take this as sarcasm (I hate typed language, no inflection at all and things are often taken the wrong way). For a guy like me to get info from you is like a model rocketeer getting to talk to Dr. Von Braun. Not that you are a saint or anything like that, but I appreciate the years of work you have put into your craft and the fact that you so unselfishly give what you have learned. I hope I dont sound like Im placing an offering at the alter of Cashen. :) Just wanted to say thanks. My learning curve has been greatly reduced thanks to reading your work.

Sean

Kevin R. Cashen
01-06-2011, 08:30 AM
Thanks, I have seen similar pictures but did not know how they got there. This is information that I will probabaly never use but interesting to be exposed to. Again thanks and you have just convinced me that If I need to know about the interior of the steel I need to check with you and not start trying to do it myself.

I am not trying to discourage anybody from doing whatever they can to increase their own personal knowledge, I just always like to make it clear that if somebody just wants to make nice knives a metallographs is extreme overkill and not at all necessary. Also, as has been mentioned, what is revealed in the microscope eyepeice still needs interpretation by somebody who knows what they are looking at and what they are looking for. Kind of like even if you gave me a X-ray of somebody with internal problems despite having a picture of everything inside I would still not be able to diagnose a thing.

Kevin R. Cashen
01-06-2011, 09:28 AM
I'm one of those curious/cantankerous sorts who hears the conventional wisdom and says, "Ok, but why? Can you show me?" Not as a challenge, simply because I really do want to know. It's fascinating stuff! I very much appreciate how much some makers do to encourage reasonable questions and look for real answers. Thank you Kevin!

I have noticed that about you James, and I like it. I am pretty much the same, My friend Roman Landes like to stress the importance of the word "why?" if we were all like annoying children with that word, continually asking for clarification and verification, what wonderful filtration would occur in information and much grain would immediately be separated from chaff.

James Terrio
01-06-2011, 09:53 PM
That's encouraging Kevin, thanks. Sometimes I have asked the right questions of the wrong people and ending up with both of us looking like stubborn mules. I'm learning to pick my battles a bit better ;)

Kevin R. Cashen
01-07-2011, 08:14 AM
Metallography is just one more method of analysis in getting what I often refer to as the big picture. What we are doing with all the thermal and mechanical treatments on our steel leave it in a certain condition, trying to determine the exact nature of that condition is like assembling a jigsaw puzzle to make out the details of this picture it represents. If all you want to do is make a reliable knife then you don’t need every puzzle piece to get an idea of where you are at. But if you want to really get into every property you are messing with in the steel you need more and more pieces of the puzzle to make out more of the picture.

The more variables you have to contend with, the more pieces of the puzzle you need. Many people feel that digital controllers and using known steels with exact chemistry are for geeks like me who insist on most of the puzzle, but in fact it is the guys who work with only portions of the puzzle that need tighter controls with less variables; I can handle quite a few more variables and mysteries by being able to see more of them.

In experimenting I often get odd Rockwell readings. That test only gives me a number for a specific property (just one piece of the puzzle) but it can’t tell me why I got that number; the microscope can then fill in a large chunk of the puzzle and help explain the numbers. But all of them will remain unrelated bits if you don’t have the most powerful puzzle solving tool of all- the knowledge to interpret all the results.

Interpretation of the results is the key to it all. One of the biggest pitfalls and the source of the vast majority of misinformation in our business is misinterpretation of the results, and tests that give us very small pieces are easy to misinterpret. And, of course, when pieces that don’t even go to our puzzle get mixed in misinterpretation is inevitable.


That's encouraging Kevin, thanks. Sometimes I have asked the right questions of the wrong people and ending up with both of us looking like stubborn mules. I'm learning to pick my battles a bit better ;)

As it probably quite evident, I love questions of all kinds. Well all kinds except one, I don’t appreciate insincere questions, the ones people ask when they already have the only answer they want and will dismiss any information that doesn’t fit that template. Indeed the only thing learned in that situation is how stubborn we can be.

Denny Eller
01-27-2011, 01:31 PM
Why are the intelligent so uncertain and the ignorant so cocksure?

jwstarr
03-09-2011, 11:10 PM
Hay Kevin thanks for all input. After thirty years of knifemaking and reading every thing I can about what takes place in the hardening tempering forging ect. I thing that I still dont understand but a small percent of it but I am still learning thanks to people like you . Keep it coming!!!!

jw