Hypereutectoid steel

bambright said:
Kevin,

..Between grain refining vs carbon distribution, which one we should do first and why?..
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Easy- get the carbon where it needs to be first. Grain refinement is a very quick an easy fix if you know what you are doing.

bambright said:
To complete the picture, I know you have been sharing this before but I would like to ask you again to provide the example of your O-1 heat treatment along with this thread for both with spheroidized and non-spheroidized so we are clear exactly what, how, and why.

Thanks, bambright
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http://www.cashenblades.com/Info/Steel/O1.html
 
I'm about to forge O1 for the first time today so I'm paying attention very closely. Thanks for all the input and sharing with the community.

Carpenters HT spec for O1 says once at temp for hardening, soak for 5 minutes per inch of thickness and your O1 pages says soak for 10 to 30 minutes. Could you explain the difference in suggested soak times and the reasons?

Thanks again.
 
Greg Obach said:
...question...
since i'm not equipped for controlled subcritical anneal.. .. i'm curious... because once or twice i've drilled some steel barstock that was suppose to have been annealed... and the drillbit chattered alot... ..which is excactly what i expect from the crucible steel barstock ( i'm vary familiar with that )... but this was from the factory... huh...
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Very common, particularly in 1095 these days. A lot of the 10XX series steels I have cross sectioned for under the microscope have a segregated stringer of concentrated carbide running right up the center, often this will include grain boudary cementite so heavy that it can be seen macroscopically. This is why proper normalization is so important and why forging too low to move this stuff around is not improving anything and can even make it worse.


Greg Obach said:
...can the subcritical anneal produce carbides that coarse if the process wasn't watched closely.... what are the limits to the process... or can they run the size of this up to what i'm used to seeing?
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What you see in the crucible steel are more the overall effect of carbide networks, very much like the segregated stringers I described in the center of the 10XX series. Spheroidizing can form individual spheroidal carbides that arrange themselves within these networks. If one goes above Ac1 and then cools slow enough to really tap into what is known as the divorced eutectoid reaction you can really gather the carbon together to make very widely spaced and large spheroidal carbides. This will make the softest possible steel for working on but will require an appropriately longer soak time to put back into play.

Greg Obach said:
...
another thing... with the popularity of hyperetectoid steels in knifemaking.. why hasn't there been more discussion on the " what to do with the extra carbon "... ... is it just superfluous to the modern knife... ! maybe our expectation of carbon steel is lower due to the popularity of stainless steel.
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I feel it is lowered expectations do to the oversimplified views of steel and its treatments. "Cashen you are full of &^%, I heat treat 1095 the same as any steel and when it comes out of the goo quench it skates a file just fine!" Our penchant for relying on one simplistic test as definitive allows us the luxury of ingorance as to all the differences in steel. It cuts rope, it bends in a vice, then it must be perfect, and in no need of fixing.

Greg Obach said:
...
another question... what about tempering carbides.. i know there small but can they be a problem.. .. pending on temp and where they are?
( sorry bout my ignorance but i don't know much about this at the moment )

G
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Tempering carbides don't really come into play until you go to 400F or better. Then enough carbon as gatherd together to form a superfine carbide. These intial carbides are often reffered to as epsilon and other Greek letters and are not even visible under an optical microsope but their overall effect can be seen as a darkening of the martensite. By this intial nature they are very fine a very widely dispersed so are often much friendlier to our purposes than the previously discussed primary carbides. As you continue to go hotter in tempering the carbides will get courser until they do become visible under the microscope. Tehn by the time you apporaao 900F you are begging make large spheroidal cementite particles and we should start calling it spheroidizing instead of tempering. When the fine carbides are not friendly is when they form sheets between the martensite lates or plates resulting in TME or tempered martensite embrittlment. This is the cause for that annoying dip in impact toughness in tempering from 450F-550F in steels with certain alloying, moly being just one of the culprits.
 
Subcritical anneal should be explained in some more detail .There are two types.
If we start out with pearlite as would be the case with a low hardenability steel that is normalized, that's case #1. This structure ,sometimes found in the 'annealed' condition is very difficult to machine.If we heat to ~ 1200-1300 F the carbide layers in the pearlite slowly form spheres .The longer the time the larger the spheres .A coarse structure.
The case # 2 is when we normalize a high hardenability steel and get martensite. Heating this will precipitate fine carbides as Kevin has explained.As the time increases the carbides gather more carbon and get larger. This is the mechanism for any precipitation in metals.The earlier stages produce stronger structure as the particles have coherency with the matrix.
Case #1 produces the highest machinability but is not as good for further HT as the spheres require more work to dissolve and diffuse.
Case #2 has finer carbides ,easier to further HT an end up with finer carbides which makes a better blade....So Q&T to anneal ? Sure .
 
DELETED dumb wordplay.It has been a long day.

GOOD stuff, Kevin!

I appreciate all the one and two syllable words.

Helps me when I am looking them up in the dictionary!

Shutting up now.

Shane
 
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69_knives said:
I'm about to forge O1 for the first time today so I'm paying attention very closely. Thanks for all the input and sharing with the community.

Carpenters HT spec for O1 says once at temp for hardening, soak for 5 minutes per inch of thickness and your O1 pages says soak for 10 to 30 minutes. Could you explain the difference in suggested soak times and the reasons?

Thanks again.
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perhaps
 
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Gotcha.

As a somewhat relevant tip, I picked up a $9.00 multimeter with a temp guage and have it stuck in my forge right now, I'm not sure how high it will read, poor documentation but it is reading over 1000 deg C, so with a really cheap tool one can ahve fairly accurate forge temps for HT.
 
Thanks Kevin: I have tried to absorb this info before from other sources and soon my eyes glazed over and the fog got thicker. You have helped clear some of that fog.
 
haha... Kevin has that vulcan mind meld ability... to get past our primitive emotions and communicate with us... ;););) ... ( just teasin bros )

i got it now... i'm in better shape about the sub-critical... and the message did get through about carbides... its funny but just the word carbide is usually a positive ! ...

eg..

" oh ya,,,, sniff... that steels got... extra carbides...." ( said with a Ralph Furley like confidence !)

now less confidence and more questions are raised such as to where they are ?

i have to say that it is abit familiar... i must have casually read it or really glossed over it but this never sunk in... .. i see it now... and i see how it could be a big time problem...

thanks guys for taking the time
Greg
 
Good info Kevin. :)

I have a question though... (purely hypothetical), Lets say you were working with a "hypererectiod" steel with a simple blacksmith type shop set up, and you couldn't nail the subcritical annealing. So,... you slow cooled it from above critical, slowly enough to soften it for stock reduction. What would be the best way to fix it, (if any), before quenching? Could you simply run a series of say three normalizing (air cooling) cycles from progressively lower temperatures with the final cycle being just slightly above non magnetic or something of that nature?
 
Excellent info! Thanks again Kevin. Now on to my question. :)

So, what can be expected when a hypereutectoid steel (let's say 1095) is used in damascus with another high carbon steel (let's say, 15n20)? Let's assume about 66% 1095 and 33% 15n20 (since this works out about right for the common mix of 3/16" 1095 w/ .058" 15n20 from Kelly Cupples...I like to keep things grounded in the practical, as well as what I have in my shop ;) )

What could one expect to see after welding but prior to any other work? The drop in carbon from the mix will bring me close to being a eutectoid steel, but I'm wondering if there are any hidden "gotchas" because I started with a hypereutectoid steel.

Thanks,

-d
 
The science is interesting, but I guess what I'm trying to get at is, (without getting into a debate over the "idealistic" nature of science versus the "pragmatistic" nature of smithing),... are there some simple rules of thumb in terms of processing the steel, that we can observe regardless of the type of set ups we have... or how to get the most out of what we have rather than a debate over which is better or best,... without being accused of over simplification?…

Couldn't we say something along the lines of,... Avoid slow cooling hypereutectiod steel from above critical except as a last resort, in which case normalize it real good before quenching it?
 
Tai Goo said:
Good info Kevin. :)

I have a question though... (purely hypothetical), Lets say you were working with a "hypererectiod" steel with a simple blacksmith type shop set up, and you couldn't nail the subcritical annealing. So,... you slow cooled it from above critical, slowly enough to soften it for stock reduction. What would be the best way to fix it, (if any), before quenching? Could you simply run a series of say three normalizing (air cooling) cycles from progressively lower temperatures with the final cycle being just slightly above non magnetic or something of that nature?
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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.
 
deker said:
Excellent info! Thanks again Kevin. Now on to my question. :)

So, what can be expected when a hypereutectoid steel (let's say 1095) is used in damascus with another high carbon steel (let's say, 15n20)? Let's assume about 66% 1095 and 33% 15n20 (since this works out about right for the common mix of 3/16" 1095 w/ .058" 15n20 from Kelly Cupples...I like to keep things grounded in the practical, as well as what I have in my shop ;) )

What could one expect to see after welding but prior to any other work? The drop in carbon from the mix will bring me close to being a eutectoid steel, but I'm wondering if there are any hidden "gotchas" because I started with a hypereutectoid steel.

Thanks,

-d
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You pretty much have it figured out, diffusion will take care of things quite well. Since steel phases will always prefer equilibrium if you have a lower carbon steel next to hypereutctoid material, the carbon will head for that o#08-[[[[[[[[[[[[

In any case, a good series of normalizations with reducing heats o the billet are always a good idea with damascus, before stopping for the day.
 
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Tai Goo said:
Good info Kevin. :)

I have a question though... (purely hypothetical), Lets say you were working with a "hypererectiod" steel with a simple blacksmith type shop set up, and you couldn't nail the subcritical annealing. So,... you slow cooled it from above critical, slowly enough to soften it for stock reduction. What would be the best way to fix it, (if any), before quenching? Could you simply run a series of say three normalizing (air cooling) cycles from progressively lower temperatures with the final cycle being just slightly above non magnetic or something of that nature?
Click to expand...

You may remember. Silly me, I have succeeded to do that for D2 in a temp controlled kiln. Mete and Kevin came with that solution... : http://www.bladeforums.com/forums/showthread.php?t=602818
 
Kevin R. Cashen said:
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.
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O.K. Kevin, thanks. That's what I thought. :)

However, the "modern edge packing myth" must have had more to do with starting forging from higher temperatures and working through lower temperatures, heating and cooling rates etc,... as the blade became closer to the finished dimensions. This seems only natural in the finishing and straightening heats to avoid or minimize scale and decarb etc. The "old packing myth" probably had more to do with working slag inclusions out and/or work hardening the edge. However, I'm not really sure how all that started.
 
galadduin said:
You may remember. Silly me, I have succeeded to do that for D2 in a temp controlled kiln. Mete and Kevin came with that solution... : http://www.bladeforums.com/forums/showthread.php?t=602818
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I remeber that! :)

In essence, as far as I know,... there isn't much that it won't fix aside from existing factures, porosity, inclusions, impurities, decarb, scale or contaminations of any kind...

When in doubt,... normalize it with a series of progressively lower temperatures using as few heats as possible, or practical, before quenching it... :)
 
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Tai Goo said:
The science is interesting, but I guess what I'm trying to get at is, (without getting into a debate over the "idealistic" nature of science versus the "pragmatistic" nature of smithing),... are there some simple rules of thumb in terms of processing the steel, that we can observe regardless of the type of set ups we have... or how to get the most out of what we have rather than a debate over which is better or best,... without being accused of over simplification?…

Couldn't we say something along the lines of,... Avoid slow cooling hypereutectiod steel from above critical except as a last resort, in which case normalize it real good before quenching it?
Click to expand...

Much of my point in this thread is that problems can arise by approaching so many variables and possibilities with any type of one size fits all treatments. If we want to narrow it down to very simple approaches we need to then limit our focus to just one issue at a time. If all we want to worry about is annealing then we can say it is as simple as avoiding slow cooling from a high heat. But a whole new set of issues will arise in normalizing, hardening, and forging. The best way to be able to handle all of these situations is to take up the approach of learning the underlying causes and effects in the steel itself so that you can apply that knowledge in any situation. When I am being instructed on something, i.e. “never press that button!”, “why not?”, "you don’t need to know that all you need to do is never press that button!”, but what happens if somebody else presses it by mistake? I really feel it is better fro me to know what will happen and how I can deal with the consequences! Heck I may even be able to rework the system to make the red button less problematic. Thus I am never comfortable with being told "never do this" or always do it just like that" because it only tells me how to follow a recipe exactly. Should anything unexpected happen I am not armed with the information I need to adapt to it. Thus despite the number of times I am often requested to just give a recipe to follow I will try to avoid doing so. If we break the process down and teach how and why it happens we give the tools for people to write their own recipes, that may actually work.
 
 
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Kevin R. Cashen said:
Much of my point in this thread is that problems can arise by approaching so many variables and possibilities with any type of one size fits all treatments. If we want to narrow it down to very simple approaches we need to then limit our focus to just one issue at a time. If all we want to worry about is annealing then we can say it is as simple as avoiding slow cooling from a high heat. But a whole new set of issues will arise in normalizing, hardening, and forging. The best way to be able to handle all of these situations is to take up the approach of learning the underlying causes and effects in the steel itself so that you can apply that knowledge in any situation. When I am being instructed on something, i.e. “never press that button!”, “why not?”, "you don’t need to know that all you need to do is never press that button!”, but what happens if somebody else presses it by mistake? I really feel it is better fro me to know what will happen and how I can deal with the consequences! Heck I may even be able to rework the system to make the red button less problematic. Thus I am never comfortable with being told "never do this" or always do it just like that" because it only tells me how to follow a recipe exactly. Should anything unexpected happen I am not armed with the information I need to adapt to it. Thus despite the number of times I am often requested to just give a recipe to follow I will try to avoid doing so. If we break the process down and teach how and why it happens we give the tools for people to write their own recipes, that may actually work.
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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… :)
 
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