Retained austenite vs austenizing temperature

Troop

Troop

Joined
Oct 26, 2006
Messages
2,898
Quick question for you guys. Posted this on Fakebook, but all I'm hearing are crickets. As a general rule, the higher the austenizing temperature (within reason for the steel being used), the less retained austenite? Specifically for A2, but as a general rule of thumb.
- Thanks
 
Troop said:
Quick question for you guys. Posted this on Fakebook, but all I'm hearing are crickets. As a general rule, the higher the austenizing temperature (within reason for the steel being used), the less retained austenite? Specifically for A2, but as a general rule of thumb.
- Thanks
Click to expand...
You have it exactly backwards. Higher austenitizing temperature means more retained austenite.
 
Larrin said:
You have it exactly backwards. Higher austenitizing temperature means more retained austenite.
Click to expand...
Thank you, Larrin. I am trying to figure out why my old HT for A2 from 15 years ago works so well. No cryo or sub-zero treatment involved. It is the absolute WORST way to HT A2, according to everyone. Held at 1800F (yellow orange) in the propane forge for 20 mins, then marquenched at 400F in peanut oil for 10 mins, tempered 3X @400F. The thing cuts almost like D2; not sure why, but it is phenomenal. Something to do with carbide formation? Too large grain size? The edge is stable, though. No chipping or rolling after repeated chopping into seasoned oak firewood. I only lost 2/32" to decarb.
I've treated A2 in the accepted way for years, in the Evenheat kiln, then sub-zero, but when I HT it in the way I described, it out cuts the "accepted" method blade by a mile. Trying to understand why.
By the way, I just picked up a copy of your book; it looks to be unbelievable.
Thanks again for your reply.
 
You’re right, that’s the worst way to heat treat A2.

There is no secret heat treatment that will make a steel perform better than it is designed to. You can maximize the properties but in the end, it is still only A2.

You can’t heat treat A2 to out cut Rex 121or to be tougher than S7, not going to happen.

Heat treated properly, A2 will attain a certain hardness, it will have certain types of carbides and a certain volume of carbides, it will have a certain amount of carbon and alloy in solution, period.

Hoss
 
Thanks for the reply. No secrets here, I told you how I HT'ed the A2 and it came out much better than typical, and by typical, I'm mean the accepted standard industrial treatment according to all the data sheets and engineering specs and consulting with Roman Landes and Joe Szilaski.
This is the point...I KNOW that it is the worst way to treat A2, and yet?
I'm just trying to figure out why; I am perplexed about it, that's why I'm asking questions.
It should not have come out good at all. However, it produced a distinctly noticeable improvement in performance. Toughness was the same, but wear resistance was greatly improved.
I'm looking for answers.
 
Troop Troop
You know, that last post makes me sound more like an a-hole than I intended.
As an explanation let me tell you about my experiences in bow making.

I like long bows, and that's what I tend to make, but I made a brief jaunt into sinew backed short bows, and MAN did they just SPIT thoes arrows out! It blew my mind, for some reason when I shot them, it just seemed like the arrows exploded out of those little bows.
And I just KNEW that they were faster than my long bows. Then I tested them with a Chronograph. The long bows shoot faster, every time. Without exception. Same draw weight, same weight arrows, the long bows ALWAYS shoot faster. It's just simple physics, a long bow has a longer draw length, and therefore has more opportunity to impart energy into the arrow, excellarating it for longer.
The physical laws of the universe don't care about our ideas of what is better.
If something seems too good to be true, it is. There's something else going on that we're missing.
 
A.McPherson said:
Troop Troop
You know, that last post makes me sound more like an a-hole than I intended.
As an explanation let me tell you about my experiences in bow making.

I like long bows, and that's what I tend to make, but I made a brief jaunt into sinew backed short bows, and MAN did they just SPIT thoes arrows out! It blew my mind, for some reason when I shot them, it just seemed like the arrows exploded out of those little bows.
And I just KNEW that they were faster than my long bows. Then I tested them with a Chronograph. The long bows shoot faster, every time. Without exception. Same draw weight, same weight arrows, the long bows ALWAYS shoot faster. It's just simple physics, a long bow has a longer draw length, and therefore has more opportunity to impart energy into the arrow, excellarating it for longer.
The physical laws of the universe don't care about our ideas of what is better.
If something seems too good to be true, it is. There's something else going on that we're missing.
Click to expand...
Thanks again for your reply. You're absolutely right, there's something going on that I'm missing. Guys, please, don't misunderstand the reason why I posted this question. I really don't have a horse in this race....I'm not trying to brag about some super secret HT technique performed facing the North Star during the Blood Moon.
I'm just looking for answers.
OK, please allow me to ask a more direct question...."how would, If I desired to, make A2 have a toothy edge like D2?" What would cause that? Excessive grain size? Etc.
 
Troop, I’ve made knives for 43 years. I’ve seen or heard this type of thing hundreds of times, maybe more. There have been makers writing articles about weird heat treatments and their amazing results. In every case, upon closer inspection, they have a poor heat treat.

If you watch FiF you’ll see lots of poorly heat treated knives perform pretty well.

You’ll be better off studying the science and perfecting your heat treating.

Hoss
 
Don't say it...."Use D2", right? Ha ha
DevinT said:
Troop, I’ve made knives for 43 years. I’ve seen or heard this type of thing hundreds of times, maybe more. There have been makers writing articles about weird heat treatments and their amazing results. In every case, upon closer inspection, they have a poor heat treat.

If you watch FiF you’ll see lots of poorly heat treated knives perform pretty well.

You’ll be better off studying the science and perfecting your heat treating.

Hoss
Click to expand...
Are you saying that I don't know how to HT knives? Just because I'm thinking outside the box? You don't know jack squat about me. And, you're being an A-hole, again.
 
Troop said:
Don't say it...."Use D2", right? Ha ha

Are you saying that I don't know how to HT knives? Just because I'm thinking outside the box? You don't know jack squat about me. And, you're being an A-hole, again.
Click to expand...
You are criticizing one of the most knowledgeable people in the history of making and heat treating knives.

I would have said something earlier, about your heat treat but I really don’t feel it is a good use of my time to do so anymore.

a few years back, Larrin Thomas started doing research on what different heat treat does and does not accomplish. I helped by heatr treating many samples of different steels with different protocols. Chuck Bybee at AKS donated most of the steel. A few other smiths including Devin Thomas heat treated and ground out samples. Larrin heat treated a bunch too once he got his kiln set up. In EVERY case, unconventional heat treats decrease performance, other than one tweak on higher alloy steels, which is using cryo as part of the quench, rather than using high temper and cryo after temper, which (the low temper tweak) results in better toughness and corrosion resistance.

The heat treat you described with your A2 would offer no benefit in any parameter I can think of. Maybe you can made some samples with both heat treats, in the sizes needed for impact testing, and edge retention testing. The sizes are listed on the knifesteelnerds website.
 
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Troop said:
Don't say it...."Use D2", right? Ha ha

Are you saying that I don't know how to HT knives? Just because I'm thinking outside the box? You don't know jack squat about me. And, you're being an A-hole, again.
Click to expand...
Why would anyone say use D2? Low toughness, and not especially high edge holding. There are numerous steels that have better edge holding, corrosion resistance, and toughness.
 
Troop said:
Thanks again for your reply. You're absolutely right, there's something going on that I'm missing. Guys, please, don't misunderstand the reason why I posted this question. I really don't have a horse in this race....I'm not trying to brag about some super secret HT technique performed facing the North Star during the Blood Moon.
I'm just looking for answers.
OK, please allow me to ask a more direct question...."how would, If I desired to, make A2 have a toothy edge like D2?" What would cause that? Excessive grain size? Etc.
Click to expand...

Sharpen at 120 grit, and strop. Toothy edge accomplished.
 
Troop said:
Don't say it...."Use D2", right? Ha ha

Are you saying that I don't know how to HT knives? Just because I'm thinking outside the box? You don't know jack squat about me. And, you're being an A-hole, again.
Click to expand...
maybe you have some Steve Austin in your molecules and they're bionic?
 
Troop said:
Don't say it...."Use D2", right? Ha ha

Are you saying that I don't know how to HT knives? Just because I'm thinking outside the box? You don't know jack squat about me. And, you're being an A-hole, again.
Click to expand...
I’m not trying to hurt your feelings, just trying to save you a bunch time, money and frustration. You’re barking up the wrong tree.

BTW, Larrin is my oldest son.

Hoss
 
Maybe I can help here. I see some missing information in the "Old" heat treatment process that is important. After you quench in oil to 400F for 10 minutes do you then let the blades cool to room temperature before tempering? Also, are you heating the oil to make sure it is at 400 or could the oil be colder? This is important because you are essentially oil quenching an air hardening grade. Following the entire temp vs time process from start to finish is critical in mapping what may be going on.
 
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