How much martensite?

[kbaknife]

Another way of looking at how successful your austenizing and quenching went is to NOT think about how much martensite you made, but, rather, how much pearlite you avoided.
I'm just sayin'.   :cool:

[Lin Rhea]

I look forward to this one. Good subject.

[kbaknife]

Sometimes it just helps me to either look at things in reverse, or in extremes, to get a better grip on what's happening.
If that idea I gave can help anyone further understand what we're trying to accomplish when hardening a blade, then that's a good thing.
What we're trying to do is AVOID reverting to pearlite by letting the blade cool too slowly from the condition of austenite.
We need to extract the heat - during the quench - to render this possibility nill.
This forces the steel to make something else - martensite!

[kansas stik man]

well put karl, ive yet to buy some books to explain more the complicated parts of knife making but have not found any at local book store so ill have to order one on line.

[kbaknife]

Don't over-think it.
For the steels MOST makers - like us - normally use, you just need to connect a couple REALLY IMPORTANT DOTS!!! After that, there are no secrets.
It's just getting out of denial and thinking that what you're doing is ok, or sufficient, and acknowledging the fact that you're either not using steel that suits your capabilities, or you're not using the right oil, etc.
It's pretty simple - SOME steels - low alloy, shallow hardening - revert to that condition of pearlite FASTER than some steels, so we need an oil capable of sucking out the heat fast enough so those steels don't revert to pearlite!
Other higher allow, deep hardening steels take looooooonger to revert to pearlite because of all the alloy in the "way", and these steels require a slooooooower oil so as to NOT induce stresses by sucking out the heat too fast for THAT type steel.  
The steel USES the heat that's in the hot blade as energy to revert to pearlite. (It takes energy for steel to create some other type of phase of "being", just like anything else in this universe)If we suck the heat - the energy -  out FAST enough for that steel type, then it can't revert to pearlite and is forced to make something else - martensite!

[kansas stik man]

that i understand, a simple heat and time ratio right?  im curious is there a chart or book that gives or sugests what steels need which oils and temps to which you quench and temper?  what interesting to me is that for a long time working with steel and iron was understood by the blacksmiths as in what needed to take place to make a good knife  blade but was not worded in such ways that we understand it now.  metalergy is a CRAZY  thing if ya ask me.  but fun to learn all the time. not very many days that i get on here and dont read something that i didnt know.  its nice to have experianced people such as you and lin and others that are more than willing to help pass on the skills of the trade.

[kbaknife]

Not necessarily a "chart" per se, but each steel has a TTT diagram showing the phases it goes through over a given period of time at a given temp. It's our responsibility to match the correct oil to the steel.
It's really pretty simple.
For what we use - 1084, 1095, W1, W2 = fast oil.
Those are shallow hardening, low alloy steel.
They will revert to pearlite, very quickly from the condition of austenite, and need to get the heat sucked out quickly, so a FAST oil is recommended.
 Deeper hardening, high alloy steels like O1, L6, 5160 and 52100 have more alloy which require a longer time to revert to pearlite, so a slower oil is required so as to not induce any unwanted stresses from cooling to fast. For these steels, warm mineral oil or even canola CAN be effective if the maker has his ducks in a row.
Keep in mind that those steel also require a longer soak at austenizing temp. Some guys heat treat 5160 in their forge, and that just doesn't cut it in my book. 5160 really needs about a 15 minutes soak at 1525 degrees to get the most out of it. So does O1. For these reasons, the shallower hardening steels work well for the beginner, providing he supplies himself with the correct quenchants.
At the upper end of the extreme, the really, really HIGH alloy steels like stainless 440 and the other well known steels have soooooooooooo much alloy that they don't even need to be quenched in oil! They can cool fast enough in still air to avoid converting to pearlite.
Keep in mind, the higher the alloy, the longer the accurate soak time at prescribed temps to get all of the alloy dissolved into solution.

There are fantastic tutorials on many of the knife making forums that will keep you up well into the night if you want them.

[kbaknife]

I will also go out on a limb here and challenge you about the older blacksmiths knowing things we don't or are unable to understand.
They made tons and trainloads of mistakes and threw away one knife for every one they kept.
Their steel selection was minimal and undependable.
They didn't know one thing we don't know today or are not able to understand.
Go up to a metallurgist that works for Crucible steel and try telling him that the old time blacksmiths knew things that he would not be able to understand.
Things could get messy.

[Lin Rhea]

One misconception about metalurgy is that it cant be understood. That it is a mystery. While it is true that most dont understand it, some actually have a good understanding of it, but remain willing to learn even more.

The seemingly untangible nature of steel, I believe, is because the stuff we're wanting to know and "see" are inside the steel and mostly microscopic in size. Thus, it's easy to just view it as a mysterious elusive secret.

I have tried to make it a policy to view this in as simple terms as possible often comparing it to other areas or things in life. I do this so I can understand it and manipulate the process from either end of the maker's field of view. In other words, I want to skin the varmint from either end, but still make a clean job out of it.

Each steel has it's prefered recipe and when people insist on using mystery steels without adjusting the forging and treatment of the steel, well it just reinforces misinformation regarding the ability to understand it.

[Kevin Evans]

I read your guys stuff and think back when I was learning ,I found it hard to understand what seemed like big words.
After going too school and one of the first things you learned was The instructer heated a piece of steel to orange color(non magnitic)  ,put it in water and laughed and said its hard.He was correct and put it in a vice gave it a quick tug and it broke!
What was to be learned??? He then did the same thing with the steel and this time quenched in the correct oil and said its hard.Put it in a vice gave a quick tug and it sprung back in his hand.    WEll wait a minute ,he grabed it again pulled real hard and it didn't break.Acted more like a spring.
Yes then we examined and learned more about the structer of the steel.
Whats all this about well for beginners (like myself) untill you watch whats really happening you can't understand.(martinsite& pearlite,grain structure and the such)
If your making knives that means you have a forge,water, oil (maybe different kinds of oil and I know you can turn the heat up and down) get out there and play.You will be amazed at what you can learn.
This is important we are ALL learning to CONTROL the steel,some are more advanced,but believe me they are still learning ,and they are learning by exsperementing (with many failures included, just like the beginers)
Jerod its great that you want to learn ,don't be intemidated just go have fun.
OK Karl ,I know your laughing you can have some fun with my words,I don't mind.

[gudspelr]

Kevin, I tend to agree with some of your points-go out and have some fun   .  I have greatly appreciated makers like Lin and Karl who have deepened my knowledge base significantly and there is a lot to learn when chasing "perfection" in a knife.

That being said, an extremely basic knowledge level can get any guy going in this.  I am now of the school of thought like Karl said-how much martensite can I get?  I'm learning the value of maximum martensite, the different quenchants for different steels and the processes for them.  But again, a pan of "goop" after the steel's hot can make a first knife (at least it did mine).  Thankfully, because of guys like Lin and Karl and organizations like the ABS, secrets are far fewer and all a guy really needs to do is have the desire to learn.

Jeremy

[kbaknife]

Not laughing at all, Kevin.
I'm lucky to find the shop door on most days.
I've just found it easier to acknowledge to myself that I don't know something than to continue using procedures that just barely get me by.
A newer maker can can just spend an afternoon doing some reading, asking and learning, and improve a lifetime of knife making if he will just LET himself do it.
In my post above there was nothing beyond the learning ability of anyone here.
It was all just basics, and there is little more than basics needed to make a killer knife!
If I can do it, most 6th graders can pull it off.
Ya' just got to admit that you don't know and that there's room for much improvement.

[Kevin Evans]

Karl ,I would like you to talk a little about the proper hardness of a knife.You can use rothwell scale or you can just say as hard as I can get it.
Really what I'm asking is what is, the proper hardness in a hunting knife?
One that stays sharp a little longer in the field.(That you can't sharpen in the field,because its so hard)
Or one thats a little less hard and you can give a few strokes and she's ready to go again???

I know Tippet says his friends test a lot of knives but I never here what they like in the hardness ?

[kbaknife]

That's the way I like them - just hard enough to cut well and sharpen easy.
Not so hard that they're "chippy" and not so soft that they're worthless.
That sort of comes with time spent in the forge really learning your equipment I guess.
I've come to learn just how much line pressure to come in from my tank, how many turns of the needle valve and how much air to get my forge running right at the temp I want to use for my austenizing of 1095, W1 and W2.
That said, getting the right hardness is one thing, added to the right tempering time and temperature, but now we need to digress back to grain refinement!!
Similar hardness in two different blades of the same steel with dissimilar control of grain refinement will result in different sharpening and cutting characteristics.
If you don't get your grain pinned where you want it, your hardening, tempering, finish grinding and sharpening will result in poor edge retention.
We've spoken a lot about this in the past on many  threads, but without proper grain control, the rest is irrelevant.

Once again I quote Roman Landes who says, "Geometry cuts - heat treatment determines how long."

I actually like my knives so I can sharpen them on the top edge of my truck window.

[kansas stik man]

this question goes to all the experianced makers,  how long before you came across the quench hardness, temper hardness grain size and all around expections of yours knives that you build?   karl said he likes to be able to sharpen on a truck window, i too like this amount of hardness.  but how long did it take you to forge and heat treat and temper before you found the perfect results, the results you try to strive for every time now?

[kbaknife]

Originally posted by kansas stik man:
this question goes to all the experianced makers,  how long before you came across the quench hardness, temper hardness grain size and all around expections of yours knives that you build?   karl said he likes to be able to sharpen on a truck window, i too like this amount of hardness.  but how long did it take you to forge and heat treat and temper before you found the perfect results, the results you try to strive for every time now?

I still haven't found the "perfect" results, but I've gotten pretty consistent with my results.
I was doing ok after 3-4 years, but consider that at that time I didn't even own a computer or a cell phone. If I wanted to learn something I got in my truck or on my motorcycle and drove cross-country.
I drove my motorcycle from Illinois to Texas, to Wyoming, to New York, etc. just to learn from
other makers who were teaching what they knew. There was no other way!
Today, with all of the available information on the internet, forums, hammer-ins, schools, seminars, instructional DVDs, and the endless availability of high quality supplies and steel, to only mention a few, if a person TRULY!! wanted to learn enough to make a very serviceable and dependable knife that 3-4 years could be reduced to 3-4 months if the person set aside a little quality time.

[Kevin Evans]

"Geometry cuts - heat treatment determines how long.

Never heard that ,but I like it!

[akaboomer]

This is what the kind of stuff I was trying to get in the testing thread. I think all of us learn from these things, but some are further along in the learning. I have been testing alot on grain control and have begun having the results I have wanted consitantly. I am convinced it is invaluable to get the "inside" of the blade right or its waisted effort to make it pretty or perfect. An ugly knife heat treated correctly can't help but out perform a pretty knife thats a mess on the inside. I now have a substantial scarp pile of steel I have tested on but I know the knives I will finnish later won't see the scrap pile. Learning and testing have become my main focus for now.

So what kind of real world testing would you do to determine amounts of pearlite or martinsite you end up with?

Chris

[Lin Rhea]

Chris,
         In the real world, this is all manfest in the knife's performance under tough conditions.

There is two ways to know whats going on inside your blade. Seeing it (the grain size) with your own eyes and looking at evidence.  You have to correlate the two. If the evidence says "this is a tough enduring knife" it's good to be able to see why with your eyes so you can make it more "real" to yourself. So, you should do what you are doing, heat treat some blades in different ways, adjusting technique, and figure out for yourself why all of the suggested techniques work and how the steel looks on the inside. The more you do that, the fewer blades you will need to break, because you will know what techniques work and how it will affect the performance.

All of this testing should be a foregone conclusion well before the knives get out into the field. It's still good to send a knife to the field for that kind of testing, sure. But, by and large, you want any failures to happen under your control and your eyes.

One thing is always true, if there is a failure, there is a reason why. Figuring out "why' is part of trouble shooting. This is when a person starts really understanding.