Hypereutectoid steel

NickWheeler said:
...Kevin- I don't totally understand where you're coming from, but I think I do for the most part...
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Feel free to ask me to clarify anything that I am not quite communicating well, believe me you would not be the first to turn to me to ask what the heck I could be talking about:D.
 
Kevin R. Cashen said:
O.K. now that I have scared you to death with all the problems that can arise, I would like to now explain how you can avoid them and how hypereutectoid steels can be our friend and very useful for the right type of knives.

First of all, it should be readily apparent that if one wants to work with hypereutectoid steel they really need good temperature control for total success. If you do not have the tools or skill for this level of control, a eutectoid like1080 or 1084 is a much better choice.

Now what to do with that pesky extra carbon? Obviously we do not want it in the grain boundaries, or of we have alloying we don’t want it making big lunky carbides within the grains either. To avoid this we just have to watch how we cool it from solution, we need to deprive it of the time needed for it to get into mischief. Slow cooling from high temps give it this time, so when working with hypereutectoid you need to forget all those annealing operations that involve wood ash, vermiculite, or stuffing it in forge for the night. Going any slower than a steady air cooling could give you problems, but if it is enough to beat the curve you can trick that extra carbon into sticking around and forming wider carbide bands in the pearlite or many finer alloy carbides. So for these steels normalizing and spheroidal type annealing are what you should stick with. Once you put that carbon in good places, keep it there by staying below non-magnetic in other heating operations until you are ready to harden.

When you harden you have to keep your temperatures lower than with a eutectoid. Ever wonder why the recommended temperature for 1095 is often given at around 1475F but 1084 can be higher at around 1500F? It is because 1084 can take it, because it doesn’t have that extra carbon to cause problems. The recommend temperatures that bladesmiths love to ignore or ridicule because those irrelevant eggheads in industry came up with them were developed through an awful lot of study on exactly what temperature will put just enough carbon into solution to get maximum hardness and leave the rest in the from of very nicely distributed fine carbides to aid in resisting wear.

So when you have a steel well above .8% carbon be certain to normalize well without overly slow cooling, use sub critical anneals by cycling above 1100F but below non-magnetic (not only will the steel love you, your mills and drills will as well), and be careful to keep the temperatures below Accm in hardening. Unfortunately the best way to accomplish that last one is to have a well calibrated heat source. Lower temperatures and longer soaks are much better for hypereutectoid steels.

Many bladesmiths love to use complex steels and then inflate all the ins and outs into a huge mystery they have some special insight into, like the world won’t truly understand these alloys until they blaze the trail with their silly fumbling. These steels were made to do specific tasks and are understood quite well by rest of the industrialized world. Many of these “mysteries” are simply created by smiths unnecessarily complicating matters by blindly stabbing at answers with inadequate knowledge or tools, with knowledge being the most important tool. Many feel their position as a smith relies upon there being a big mystery around these things, so they scoff at this information as being irrelevant, overly technical or perhaps even robbing bladesmithing of its romance and tradition. But isn’t it nice how easily things can be recognized and dealt with by anybody armed with a few facts.
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Kevin in the first part of the thread you have the comment of doing away with the cooling in wood ash, vermiculite, or stuffing in the forge for overnight.
Can we go back to this? AND not for a reciept for spheroidized anneal (well maybe kinda) but an explaination of the two or more methods to get there?
Some who may have read this may be scratching their heads and going what the......
For those with out controlled heat who can't hold just above Ac1 then reduce step the heat. (pg32 HTG.)
For me I have read of heating to the austine region and then quench to martensite and then reheated to just below A1 and went what the......
(pg 32 MoS. Verhoeven):D
Now I read your (what may be prefered) choice is of the thermal cycling at the sub critical anneal heat levels.
Spheriodize ??? door #1 door#2....
And while your on a roll.. explain divorced eutectoid transformation (DET) I might as well go to work tomorrow with a screaming headache.
 
J D Verhoeven - Steel Metallurgy for Non-Metallurgists , p35-37
Google 'divorced eutectoid tranformation' and look through the listings for 'books.google.com. You will be able to get online versions.Just check p 35-37.
Keep a copy and read it 100 times and it might be clear.Of course to do it properly there are a number of conditions to be met.
 
mete said:
J D Verhoeven - Steel Metallurgy for Non-Metallurgists , p35-37
Google 'divorced eutectoid tranformation' and look through the listings for 'books.google.com. You will be able to get online versions.Just check p 35-37.
Keep a copy and read it 100 times and it might be clear.Of course to do it properly there are a number of conditions to be met.
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Still reading.................one moment please, or maybe a day or two.
Thanks for the pages Mete.
 
Here's a question I've been thinking about for a while, but havent been able to find someone who's tried it. When using 1095, what would happen if the quenching temperature were set somewhere around 1375 F? There would be less carbon in solution, more carbides, and lower hardness and hardenability. Would the toughness increase (less carbon and lower hardness and hopefully more lathe martensite) or decrease (possible interconnected network of undisolved carbides)? Would the higher carbide volume mean higher wear resistance, or would the lower hardness negate them, like rocks in mud. In general, I guess what I'm asking is why are the lower hardening temps set where they are?
 
I'm dealing with a hypereutectoid steel. It is W1 with 1.2% carbon (has been tested, also has 0.37%Mn). I've got a reasonable understanding of the processes needed to optimize it from this thread but I don't have specific references for normalizing or austenitizing temperatures for a steel with this amount of carbon.

What I have is this:

1995 Heat Treaters Guide ~ W1 data

Nomalizing ~ 1.10%C to 1.50%C 1600F to 1695F
Hardening ~ Heat slowly to 1400F to 1555F, using the upper end of the temperature range for low carbon contents and lower end of the temperature range for high carbon contents. The range being 0.70%C to 1.50%C

Is it reasonable to extrapolate the normalizing and hardening temperatures from the ranges?

Doing that, I get a normalizing temp. of 1624F and a hardening temperature of 1491F. Seems like the hardening temp. is higher than it needs to be. I understand I will get slightly higher hardenibility with a higher hardening temp. but I don't know if I will get into trouble, too.

What I'm intending to do is normalize 3x's with a quench on #3 and then spheroidize.

Mike
 
Another bump. So no guesses on how underhardened 1095, or underhardened steel in general, would work?
 
Now that I am back at home, respond to which question? I am not certain which ones have been addressed to your satisfaction and which are still burning at us.
 
me2 said:
Here's a question I've been thinking about for a while, but havent been able to find someone who's tried it. When using 1095, what would happen if the quenching temperature were set somewhere around 1375 F? There would be less carbon in solution, more carbides, and lower hardness and hardenability. Would the toughness increase (less carbon and lower hardness and hopefully more lathe martensite) or decrease (possible interconnected network of undisolved carbides)? Would the higher carbide volume mean higher wear resistance, or would the lower hardness negate them, like rocks in mud. In general, I guess what I'm asking is why are the lower hardening temps set where they are?
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For such a short question one can cover a VERY wide landscape with it. [[[[[[[[[[[[[ Accm to then spread back out again.

In carbon 0000000..short of maximum hardness and thus the greatest strength potential. It is all a balancing act and ongoing compromise between strength and toughness. For most knife applications if you get the treatments right things work better leaning more toward strength. So many techniques used by makers with simpler equipment lead to “issues” that we have been erring in the directi
 
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Talonite is a good example of the chunky style peanut butter system. Matrix in the low 50s with very wear resistant particles.
With 1095 you can play the games but you'll never get the best properties.
 
Mike Krall said:
I'm dealing with a hypereutectoid steel. It is W1 with 1.2% carbon (has been tested, also has 0.37%Mn). I've got a reasonable understanding of the processes needed to optimize it from this thread but I don't have specific references for normalizing or austenitizing temperatures for a steel with this amount of carbon.

What I have is this:

1995 Heat Treaters Guide ~ W1 data

Nomalizing ~ 1.10%C to 1.50%C 1600F to 1695F
Hardening ~ Heat slowly to 1400F to 1555F, using the upper end of the temperature range for low carbon contents and lower end of the temperature range for high carbon contents. The range being 0.70%C to 1.50%C

Is it reasonable to extrapolate the normalizing and hardening temperatures from the ranges?

Doing that, I get a normalizing temp. of 1624F and a hardening temperature of 1491F. Seems like the hardening temp. is higher than it needs to be. I understand I will get slightly higher hardenibility with a higher hardening temp. but I don't know if I will get into trouble, too.

What I'm intending to do is normalize 3x's with a quench on #3 and then spheroidize.

Mike
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It sounds like you have a good grasp of what would work well.
 
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Kevin R. Cashen said:
For spheroidizing, do several cycles in the 1300F range. In austenitizing for the quench you then want enough heat to get the desired hardness and no more. Around 1450F to 1475F may be fine.
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"The book" would spheroidize 1200F to 1250F, minimum 1 hour. What is happening with "several cycles in the 1300F range" that is different than that? (I'm assuming you mean with air cools between... and so you know, Sarah says, "Several can be more than two and often is more than three, but not many, in any case.".)...

My usual is to stress relieve (1200F-1250F, min. one hour) before heating to quench temp., soaking, and quenching. I feel doing that makes even bigger spheroids and makes them further apart. In this instance, that seems wrong-headed... that I want the softness of spheroidizing but want the spheroides to be as small as possible and not clumped up... to go back into solution, well dispursed, easily. Am I getting it, Kevin?

Mike
 
I was reading that when the term "water" is used as the quench medium for 1095, what is meant is actually brine.

Does it matter what 'salt' is used? Like can epsom salts be used?

What is everybody's faborite recipe; dissolve salt till an egg will float?
 
I was kind of taking the "austenizing temperature controls cabide volume and carbon in solution" idea to an extreme. I figure if toughness were needed and 1095, for whatever reason, were the only steel around, higher tempering temperatures would be the best way to go.
 
me2, yes !
69_knives, the most effective brine is a 9 % solution of NaCl in water.The water should be at room temperature. Other salts could be used but NaCl is very available.
 
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