Toughness values of 10xx steels?

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Tin.Man

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Curious if anyone has any toughness numbers of 1075 or 80crv2 or 1084 or 4340 compares to tool steels like s7 and a2 or o1 etc

Appreciate it
 
I know that the old tool steels books have unnotched charpy tests for simple carbon, L6, Cr-V steels, F2, and a few Si steels all tested by Bethlehem. I don’t think they compared to any major tool steels, though. Click on full text view and then search for unnotched charpy Bethlehem: https://catalog.hathitrust.org/Record/001045298
 
I dug into that. Interesting. They aren't AISI steels of course, but the analog to 1080, quenched from 1450F and tempered at 400F was 25 ft lb, and the 1095/W1 analog with the same heat was 18 or 19 ft lb based on the graph. That seems low to me.

Whats really interesting is the next steel they test, at .5% C, 1.3% Cr and .2% V, and that steel jumps up to 120 ft lb. Interesting because while there are no Charpy numbers for it, if you read the whole chapter on "Type 20" steels they have what's nearly an identical alloy to 80CRV2. What's old is new. 80CRV2 is the 6.5 Creedmore of steel :D
 
Ah, also of interest is this:

upload_2018-3-22_21-51-21.png

This is essentially what I was taught in tool and die. It wasn't until I got into knifemaking that I ever heard of quenching after the temper. I've probably had it explained to me before, but is this something to do with RA? More when slow cooled vs water quenched?
 
It is interesting, but unfortunately they don't report the reason why.
RA could be an explanation
 
The Tool Steels books are fascinating time capsules of metallurgy knowledge. The Hathi Trust website I linked to has the 2nd ed (1944) and 3rd ed (1962). The 1st edition is not available to view online, which was released in 1934. However, I have scanned my copy of the 1st ed and will eventually write an article about it for the website and link to it there.
 
Larrin Larrin Do you feel it's necessary or beneficial to water quench from a typical 400F temper? Is the answer variable based on the chemistry of the steel in question?

I've been doing it but would prefer to avoid it, as I have much better luck correcting warp in my tempering jig on the first try when slow cooled in still air.
 
kuraki said:
Larrin Larrin Do you feel it's necessary or beneficial to water quench from a typical 400F temper? Is the answer variable based on the chemistry of the steel in question?

I've been doing it but would prefer to avoid it, as I have much better luck correcting warp in my tempering jig on the first try when slow cooled in still air.
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I am not aware of any reasons to recommend doing so.
 
Stacy E. Apelt - Bladesmith said:
Larrin, I may have said it wrong.
What I was told by a well respected PHD knifemaker was that the transformation from retained austenite to new martensite happened upon cooling between 400F and 200F. If it cooled too slowly, the RA could resist transformation and become stabilized RA. The faster cooling sort of forced it into conversion. He said the amount of RA was generally small to start with, and the amount between the two cooling rates would require a good lab to detect.
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There are a few things that can happen to retained austenite during tempering, including:
1) Transformation to bainite (or other ferrite+carbide phases)
2) Stabilization, such as through diffusion of carbon into the austenite lowering its Ms temperature
3) Destabilization, so that it transforms to martensite during cooling
I can't think of any reason why any of these effects would occur more strongly while cooling slowly from 400 to 200°F than they would during a 1h+ hold at 400°F. After destabilization the martensite forms regardless of cooling rate.
He also explained that the rapid cooling from 900F to ambient in annealing and such was to keep the pearlite as coarse pearlite, and to not allow the formation of fine pearlite. He said coarse pearlite works and drill better.
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I'm not really following this, for the following reasons:
1) If the steel has fully transformed from austenite to pearlite then more pearlite will not be forming, fine or not.
2) More rapid cooling rates leads to fine pearlite, while slower cooling rates lead to coarse pearlite.
3) If the austenite did not fully transform to pearlite then a water quench will ensure that the remaining austenite transforms to martensite rather than the potentially softer bainite which could improve grinability.
He also said that very slow cooling from 1400F to 1000F would make spheroidite, which was the best structure of all for workability. He recommended water cooling once below 900F.
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Most of the datasheets I am familiar with will say that the cooling rate doesn't matter below a certain temperature, not that a rapid cooling is recommended. I am not familiar with that type of recommendation.
Does those sound more accurate?
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Slightly
I learned this a good many years ago, and techniques and understanding may have changed. Heck, I still talk about Troosite in a hamon.
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I don't think water quenches after low temperature tempering have ever been recommended.
 
Interesting. Ive been water cooling between tempers as recommended via this forum. With those low of temps and thin cross section it wouldnt have as much as an effect
 
Same here. Been water quenching between tempers. Always had, even in the beginning, because I didn't think there was any sort of metallurgical change that could happen once the blade had cooled down to room temp (or below with tool steels/cryo) and then was tempered. But I'm always learning, and may modify my practice after reading Larrin's post, which suggests there is "internal stress" that creeps up on you when quenching from ~300-450f tempering temps. But, it also said "slightly lower" unnotched values. I wonder how slight, and how important that really is to what I am trying to achieve with the kind of blades I usually make (high hardness hunters and kitchen knives).
 
Larrin, Thanks. I may have gotten his information wrong ... or he was not giving good info. I will change the post.

I have done water quenches between tempers for many years, too. I never found any issues. The predominant reason is time, as it takes only 60 seconds to cool a batch of blades and get them back in the temper oven. Do you see any reason it should not be done between tempers.
 
Hardness and grain size are the most important factors which affect the toughness of steel. In practice, a simple 10xx carbon steel can be as tough as any tool steel if you achieve small enough grain size. However, it is easier to achieve small grain size with alloyed tool steels (particularly thanks for vanadium) than unalloyed carbon steels; therefore, tool steel are usually tougher. I have toughness tested all steels in your list (1075 or 80crv2 or 1084 or 4340 compares to tool steels like s7 and a2 or o1). With similar hardness and grain size they are equal. Please, read my article about grain size https://www.bladeforums.com/threads/carbon-steel-blades-and-grain-size.1503062/ My fovourite steel is 80CrV2 because it easily gives high hardness and great toughness.
 
in more or less plain carbon steels, do longer soak times lead to
lower MS/MF points..? and if so, increased benefits of sub-zero
treatment as a continuation of quenching...?
 
Juha Perttula said:
Hardness and grain size are the most important factors which affect the toughness of steel. In practice, a simple 10xx carbon steel can be as tough as any tool steel if you achieve small enough grain size. However, it is easier to achieve small grain size with alloyed tool steels (particularly thanks for vanadium) than unalloyed carbon steels; therefore, tool steel are usually tougher. I have toughness tested all steels in your list (1075 or 80crv2 or 1084 or 4340 compares to tool steels like s7 and a2 or o1). With similar hardness and grain size they are equal. Please, read my article about grain size https://www.bladeforums.com/threads/carbon-steel-blades-and-grain-size.1503062/ My fovourite steel is 80CrV2 because it easily gives high hardness and great toughness.
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The results of the toughness tests on those steels are not in the link you provided.
 
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