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Anyone heat treating A8 Mod?

S

Scaniaman

Joined
Jun 15, 2012
Messages
1,432
Hi,

I have a project coming up, a larger outdoor knife, and I thought I'd give A8 Mod a try.

What are your experiences heat treating it? I actually read in a couple of places that pre heating it was a good thing even for the thin stuff we use.

Any general or specific advise on working with this steel?

I use an electronically controlled kiln.
 
Which A8 Mod do you have? There is a version being sold by AKS as "A8 Mod" which has 5% Cr but traditionally it is 8% Cr steel which is called A8 Mod. In heat treating of the normal 8% Cr version I used 1900°F for 30 minutes, plate quench, cryo, and tempered twice at 400°F. That gave about 59 Rc and high toughness. I did not use a preheat.
 
Larrin said:
Which A8 Mod do you have? There is a version being sold by AKS as "A8 Mod" which has 5% Cr but traditionally it is 8% Cr steel which is called A8 Mod. In heat treating of the normal 8% Cr version I used 1900°F for 30 minutes, plate quench, cryo, and tempered twice at 400°F. That gave about 59 Rc and high toughness. I did not use a preheat.
Click to expand...

Thanks. I was thinking 1900F/1040C and 350-400F/175-200C temper 2x2 hrs, but was unsure about the pre heat so thanks for your reply. I don't have cryo, but use a -40C freezer. I'll run a few coupons first to dial things in.

It is the 8% Cr one, I am getting it here:

https://www.nordisches-handwerk.de/...chen/stahl-nicht-rostfrei/1.2360-x50crmov8-1/
 
Larrin said:
Which A8 Mod do you have? There is a version being sold by AKS as "A8 Mod" which has 5% Cr but traditionally it is 8% Cr steel which is called A8 Mod. In heat treating of the normal 8% Cr version I used 1900°F for 30 minutes, plate quench, cryo, and tempered twice at 400°F. That gave about 59 Rc and high toughness. I did not use a preheat.
Click to expand...

I ran two coupons 4.4 mm thickness. One got aust temp 1030 C (1886 F) and the other 1038 C (1900 F), no pre-heat. Both soaked for 30 min--> plate quench and freeze -41 C (-42 F) x1 hr. Then 1x2 hrs temper at 170 C (338 F).

I checked my hardness tester with a calibration block and then tested each coupon 8 times.

1030 C coupon: average 60.5 Hrc

1038 C coupon: average 55 Hrc

I am a little surprised by both the values and their difference. I'm gonna go with 1030 C of course, but up the temper a little maybe.
 
That sounds like a crazy difference for 8° C difference. Could there have been a slight decarb or sth else?
 
We can think up a bunch of things you might check. Or you could just do it over again. You messed up somewhere.
 
Larrin said:
Which A8 Mod do you have? There is a version being sold by AKS as "A8 Mod" which has 5% Cr but traditionally it is 8% Cr steel which is called A8 Mod. In heat treating of the normal 8% Cr version I used 1900°F for 30 minutes, plate quench, cryo, and tempered twice at 400°F. That gave about 59 Rc and high toughness. I did not use a preheat.
Click to expand...
Hi Larrin, are you tool wrapping your A8MOD?

Been doing some experimentation with it and was finding I could get a higher hardness when tool wrapped? Interested in your thoughts.

Thanks a lot, Francis
 
So just a question here guys, So I've seen 2 different recipes for A8 Mod.
1900°F +300°F = 61-62 HRC
1900°F +400°F = 58-60 HRC
To my understanding at the 300° temper is for edge retention and the 400° temper is for toughness. Am I understanding this correctly? A8 Mod is all new to me.
 
I would go with the 1900F, quench, cryo or, at least, -70C for half an hour, then two 400F degrees temper. But please ask Ryan Rodriguez (can't remember his name here at the forum right now, sorry), Larrin Larrin or Fredrik Haakonsen. You can find Fredrik on Facebook, haakonsenknives.
 
D.Gray said:
So just a question here guys, So I've seen 2 different recipes for A8 Mod.
1900°F +300°F = 61-62 HRC
1900°F +400°F = 58-60 HRC
To my understanding at the 300° temper is for edge retention and the 400° temper is for toughness. Am I understanding this correctly? A8 Mod is all new to me.
Click to expand...
Selecting a tempering temperature for hardness-toughness balance is not unique to A8 mod. You should read up on tempering: https://knifesteelnerds.com/2018/04/23/what-happens-during-tempering-of-steel/
 
hugofeynman said:
I would go with the 1900F, quench, cryo or, at least, -70C for half an hour, then two 400F degrees temper. But please ask Ryan Rodriguez (can't remember his name here at the forum right now, sorry), Larrin Larrin or Fredrik Haakonsen. You can find Fredrik on Facebook, haakonsenknives.
Click to expand...

It's been awhile since he's posted here
I follow him on IG

S Seedy Lot might be able to help, too?
I have a couple blanks of it from him
 
All I can add is I have experienced different heat treat response from different steel providers. I was trying to hit 61 Rc from A8M from a French source and only reached 59-60 Rc while a blank in that batch from AKS hit a solid 62 Rc.

If I wanted tough with more edgewear I would choose a different steel instead of trying to eke out a little more performance by increasing hardness on A8M.
 
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