Hypereutectoid steel

[cdent]

It still may be preferable to persue the facts. Chances are they can be repeated and confirmed even if there is a risk of misinterpretation.

Can I ask, in general, is it preferable to spheroidize martensite rather than pearlite?

Thanks much for the info and a great thread, Craig

 

[Tai Goo]

It still may be preferable to persue the facts. Chances are they can be repeated and confirmed even if there is a risk of misinterpretation.

Can I ask, in general, is it preferable to spheroidize martensite rather than pearlite?

Thanks much for the info and a great thread, Craig

Let me reapeat myself after editing my last post.... "You must have some facts to work with. That's a given!"

However,... some people can have a zillion facts and still come up with the wrong conclusion, and some need only a few to come up with the right conclusion. That is also a given!

 

[Kevin R. Cashen]

I think that's fine as long as we don't get "lost" in it and lose sight of what we are trying to do, (how we want to do it and why), become more confused or misinterpret the facts and come up with bad recipes or false conclusions. I’m sure you’ve seen that happen as much as I have. It happens...

However, you must have some facts to work with. That's a given!

There needs to be a “pragmatic balance”, between the details and the bigger picture on a more individual and personal basis…

There needs to be that balance for you. Everybody has their own desires and approaches that they can choose. Nobody needs to do anything I have presented here, we are all free do as we please, we can pick and choose any part of this thread we like, we even have the freedom to ignore this thread entirely if it does not suit our tastes.

You see I prefer to just give the basic facts as to how things happen; I am not in the business of telling people what it is that they are trying to do (how they want to do it, or why). I, nor anybody here, is the arbiter of what the big picture should be, I think that is up to each an every individual who decides to make a knife.

 

[Mike Krall]

Yes, heat is the ticket. Low temp normalizing may only make it worse since the carbide networks are already there, the carbon will want to move in and join it as soon a the lower critical is reached. However if you go very high, above Accm or the upper critical temperature, you will then dissolve it and put it back into solution, however this will most likely result in grain growth which will then have to be taken care of with a few subsequent lower temperature cycles.

I remember, as I am sure you do, when normalizing was seldom discussed or taught by bladesmiths, this was back when most of the myths surrounding forging, such as edge packing, were the dogma of the day. When I selected Jim Porter to test under I was happy to find that I had picked a master smith who was happy to hear that not only did I know what normalizing was, it was an integral part of my heat treating regimen. This is all worth mentioning due to the irony of ignoring such a critical procedure while assigning virtues to forging that are really only the result of normalizing effects inadvertently occurring during the forging heats, but many undesirable things can happen while forging that only normalizing can properly fix.

How long a time above Accm to do this?

Mike

 

[Kevin R. Cashen]

Accm is the upper limit, here you are done. Accm is the line between having some carbide left and having none with only saturated austenite remaining, so you wouldn't be to Accm unless you have already obtained this goal, you can look at it as using overwhelming heat to get there regardless of time. If you went there quickly you may keep it there a couple of minutes but if you paced yourself you can consider it done. Remember that since there is nothing but solution there will be nothing to keep the grain boundaries in place and there will be grain growth. Staying there for extended periods will allow the grains to grow to enormous size and require more effort later on to return them to normal.

This is where forging can help. To do this treatment with heat alone and hold it at the temp will result in unhindered grain growth, but if you do it while hammering the strain energy being constantly introduced to the steel from the hammer will drive recrystalization and keep grain growth under control. Proper forging is balancing the rate of deformation with that of the processes occurring within the steel, too little deformation with too much heat and the diffusional processes will get away from you, too much deformation with too little heat and the accumulating effects of strain can get away from you.

I really do want to apologize to any readers who do not have access to a metallurgy text for the use of a term like Accm. I really didn't want to resort to its use but I could not give a specific temperature since it will change with any alloy given. Accm is the designation that applies to this point with any hypereutectoid steel. It is just the temperature where all extra carbon is dissolved, and there are no islands left in the lakes, and no carbide in the grain boundaries.

 

[Kevin R. Cashen]

It still may be preferable to persue the facts. Chances are they can be repeated and confirmed even if there is a risk of misinterpretation.

Can I ask, in general, is it preferable to spheroidize martensite rather than pearlite?

Thanks much for the info and a great thread, Craig

This is truly a great question. Pearlite spheroidizes very differently and much more slowly than martensite, unless it is very fine pearlite. The lamellae of carbide in pearlite will spheroidize like a string of pearls over greater times and the courser the pearlite, the greater the effect will be. So if you made the pearlite by very slow cooling spheroidizing would not be so smooth. Very fine pearlite will produce many more fine spheroids in a shorter time and martensite will produce the finest in the shortest time.

I have many images of spheroidized martensite but none loaded to the net right now, they do not follow lines like this they are instead whole fields of well scattered fine little dots.

 

[mete]

He keeps showing the same picture ! But it's a good example.
To clarify - grain growth occurs by a grain absorbing an adjoining grain.Therefore the grain boundary must move.Elements like vanadium collect in the grain boundaries and slow the movement of the grain boundary. Vanadium then doesn't 'refine' the grain. Grain boundaries have larger space for things to happen , good and bad .Such as collecting vanadium or collecting carbides .There also is higher energy in the boundaries so reactions can start there such as the martensite transformation. More grains => more grain boundaries => more initiation points for transformation. Smaller grains gives better toughness.
Another point about carbide size .Comparing 154CM and CPM154 - they have the same chemistry so basically differ only in carbide size. The CPM has smalller and more uniformly distributed carbides. Both makers and users like that. Easier to grind,polish, sharpen. Keener edge and better wear resistance.
That's why the dicussion often comes to smaller carbides and smaller grains !!

 

[mete]

http://www-g.eng.cam.ac.uk/mmg/teaching/typd/
Here are a few pages of explaination of the iron carbon diagram and the eutectoid reaction from those nice guys at Cambridge !

 

[Tai Goo]

There needs to be that balance for you. Everybody has their own desires and approaches that they can choose. Nobody needs to do anything I have presented here, we are all free do as we please, we can pick and choose any part of this thread we like, we even have the freedom to ignore this thread entirely if it does not suit our tastes.

You see I prefer to just give the basic facts as to how things happen; I am not in the business of telling people what it is that they are trying to do (how they want to do it, or why). I, nor anybody here, is the arbiter of what the big picture should be, I think that is up to each an every individual who decides to make a knife.

I agree, and that's exactly right!

However, there are all different kinds of facts from different states and perspectives,... but I don't think we all need a scientific explanation for how the lint got in our belly buttons etc., as interesting as that may be!

Don't get me wrong though... I enjoy reading it. Keep it coming!

 

[fitzo]

...However, there are all different kinds of facts from different states and perspectives,... but I don't think we all need a scientific explanation for how the lint got in our belly buttons etc., as interesting as that may be! ....

No one seems to be forcing it down anyones throat. Not everyone may be interested in what is being discussed in this thread; that is fine for them. But there ARE plenty of particpants who obviously DO have that interest, which is the audience Kevin is addressing. They have as much right to learn as those who prefer a different way.

Let them do that, Tai. You want to promote something else, do like I said last time...start your own thread.

 

[Kevin R. Cashen]

He keeps showing the same picture ! But it's a good example...

That is so true! But to put new images up I need to resize them in photoshop, re-archive them in my home files, run them through the FTP program to cashenblades.com, use up the required space at cashenblades.com, and then get the appropriate link into my posts...
I am just too lazy to go through it all anymore. Also I have many images reserved for inclusion into published material, the stuff I have already put on the net is not as fresh so can be re-used again and again.

 

[Kevin R. Cashen]

...Let them do that, Tai. You want to promote something else, do like I said last time...start your own thread.

And if I am not mistaken Fitzo, not single one of the metallurgical minded guys interfered with or disrupted the thread Tai started, they were happy to let him do his own thing.

 

[69_knives]

I agree, and that's exactly right!

However, there are all different kinds of facts from different states and perspectives,... but I don't think we all need a scientific explanation for how the lint got in our belly buttons etc., as interesting as that may be!

Don't get me wrong though... I enjoy reading it. Keep it coming!

Carpenters instructions for hardening O1: heat it, soak it, quench it.

 

[Kevin R. Cashen]

...However, there are all different kinds of facts from different states and perspectives,...

"Everyone is entitled to his own opinion, but not to his own facts", and that is a fact.

 

[delbert ealy]

However, there are all different kinds of facts

A person who does not believe in absolutes!

 

[Tai Goo]

Do you really want me to explain what's wrong with this thread?...

If I thought it were strictly about metallurgy and facts, it would be a different story. If Kevin could really just stick to the facts, like Mete does so well,… I would like it much better. It’s the mixing of science with personal opinion, agenda, pet peeves, false assumptions, personal disclaimers, little digs etc., etc., etc., … that bothers me.

There is a lot of good information on this thread from Kevin, but weeding through some of the nonsense degrades it and takes a lot of the fun out of it. It's almost like it's more about what's wrong with everyone who's approach is different than Kevin's, than it is about hypereutectiod steel...

 

[cdent]

Hey Tai,
Help us out with the 'real' facts and let the forum members decide. Tell us about your process and let the reader decide. An opinion about what's wrong with the thread doesn't advance the learning of the facts, though the opinion is just as valid as any other.

Pure opinion here, take care, Craig

 

[Tai Goo]

Hey Tai,
Help us out with the 'real' facts and let the forum members decide. Tell us about your process and let the reader decide. An opinion about what's wrong with the thread doesn't advance the learning of the facts, though the opinion is just as valid as any other.

Pure opinion here, take care, Craig

What kind of "real" facts are you looking for?

LOL

...I guess you'll just have to weed through my nonsense and pet peeves, and pick them out too!

 

[cdent]

Thanks for revisiting Tai. I should have typed me instead of us. I'll dig around in the shed for the old weeder, and by the way, I like the link on your site for the great Phals.

Take care, Craig

 

[Kevin R. Cashen]

Edit- This thread was made in the spirit of sharing constructive information, I have edited this post so that this thread could reflect that spirit, instead of giving in to the divisive influence of intolerance. My all who read this thread learn to make knives from it, instead of how much we may disagree. – edit.