How to Heat Treat 52100

shqxk said:
Lets see if I can make sample pieces and ship it to you since I dont have milling and surface grinding machine to finish up the piece to exact size. I also have some interesting steel which would be nice to test, it is Daido's GO5. This steel is close to 80crv2 in composition and its seems to tougher than 5155 with higher wear resistance than 52100 (noticeable harder to hand sanding).
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I don’t have a surface grinder myself. You can ship it to me, and i’ll Include it in one of my batches, or another grinder can volunteer to grind it for you. My e-mail is in my profile. E-mail me and I can send you my address if no one else volunteers to grind it.
 
Working on some right now. Curious about cycling for finer grains but still using the DET and high Austenizing.

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shqxk said:
Yes! if marquenching and soak it long enough we will get some bainite structure.

But I only quench and lets it equalize for 2 minute to avoid bainite as much as possible.

I have tried austempering in 450F salt for 4 hours and have it tested at 60hrc but it doesn't seems to hold an edge very well compare to regular heat treat.
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Ok. Should be interesting if you made a coupon for Larrin to test that austempered 52100.

One guy here in Europe let it in the salt pot only half an hour and he claims to have a mixed microstructure of bainite and martensite, giving a 15-20% toughness increase (his words). He has access to industrial heat treatment facility, in Sheffield, UK, so he knows what he’s doing. I have a Karambit made in collaboration between him (laser cut the blank and heat treatment) and Doberman Knives (design and finish product), but haven’t properly tested yet, it’s more a collectors piece, but fully functional.
 
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This question is for Larrin specifically. I have been thinking about the 8th figure in your article, which is the plot of toughness (Y-axis) against tempering temperature (X-axis). Please forgive my limited understanding of your testing protocol. As I understand it during a Charpy test the material can deform one of two ways: brittle deformation (where the material bends to a certain degree then shears or breaks) or plastic/ductile deformation (where the material just bends). Did you see just one type of deformation during this testing, or both? If you saw them both it would be very interesting (to me at least) when this transition occurred relative to the tempering temperature. I assume that all the samples tested in figure #4 (full hardness?) underwent brittle deformation. Thank you.
 
Almost all of the knife steels I have tested have been all, or primarily, brittle fracture. There can be mixtures of both. And sample size matters. The thin samples we use are more difficult to interpret because the shear zone is most or all of the specimen.
 
shqxk said:
Pre-quencing combined with this technique get me 64-65HRC after 30 minute 360F tempering in salt baht (quenched in fast oil).

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What Hardness tester is that? Phase 2 digital with load cell?
 
DeadboxHero said:
This is Larrin's DET protocol
It made the best 52100 knife so far.

66rc after tempering, very stable and cut longer than the other protocols I've done on rope.
I'm very happy with the Performance compared to other protocols I've used and tested.

Have you tested? Give it a try.

Cleaned up nice too.

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Do you use foil wraps for 52100?
 
DaveDM said:
Do you use foil wraps for 52100?
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the samples needed for charpy require tight tolerances to 2.5mm so I need some wiggle room with this piece steel being a little over 3mm, I cant afford to loose .020" each side to decarb with normalizing and cycling so I wrapped it. That way it's only exposed for Austenizing.

For the blades nah, I'm grinding it away anyways since I'm doing full thickness. 52100 is a breeze to grind so I'm not concerned.
 
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samuraistuart said:
My thoughts on the annealing procedure for stock removal guys....The divorced eutectoid transformation (DET) is usually done at the mill. Or maybe better stated, "should" be done at the mill. From Verhoeven's "Metallurgy of Steel" concerning the DET anneal, "It requires no quenching and is therefore used in industry to produce the spheroidized structures of cementite + ferrite in which these steels are supplied from the steel mill." For stock removal guys, there should be no need to perform this procedure. And to that point, there should be no need to normalize or cycle it, either.
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Bumping an old thread because it seems appropriate to put this comment together with the original content.

First, I just want to say, Thank you Larrin for writing these articles.... Amazing.

Second, I'd also like to follow up on the comment above about how if you're doing stock removal, this DET anneal *should* be done already at the mill. This seems too risky assume, given that the experimentation shows it makes a big difference in the final result.

For example, Alpha Knife Supply's 52100 payge says the following: "This alloy and all our alloys have been properly annealed. You do not have to do any non-standard wasteful processes to harden the steel. Follow the heat treat recipe and the steel will get hard."

But I called them and asked what the process is, and their reply was "I'm not sure, it's whatever they do at the factory.. but it's the proper process"

Is there a way to buy 52100 and know what you are buying?
 
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There are two basic types of annealing, sub-critical and cycle annealing.

Most mills use a cycle anneal. Annealing requires heating to slightly above A3 and slow cooling. The faster it cools, the harder the annealed material and the smaller the spheroidite, the slower it cools, the softer the material is and the coarser the spheroidite carbides.

The smaller the carbides, the faster they dissolve during austenitizing, the larger carbides require higher temperatures or longer soak times to dissolve and go into solution.

DET as recommended by Verhoeven, produces a very fine microstructure.

Sometimes it’s necessary to normalize, thermal cycle, and anneal to give you the best structure.

Most mills anneal in the medium size spheroidite and should be fine to austenitize, quench and temper as is.

Hoss
 
Man. I just heat treated a knife in 52100. I tempered, did cryo (probably should have skipped it, but wanted to see how it would go) then hung it up to warm back up, and waited for my kiln to cool so I could temper it.... Man that was a mistake. It literally split down the middle long ways. Never seen anything like it.

Looking at it, I think I should have probably normalized at 1700 or held it longer at 1650 after forging, maybe skipped the cryo, and DEFINITELY got it into temper right away. I wanted to not use the toaster oven on this one, but looks like it's not an option. I'll just go a little bit low temp for the first cycle right away in that, then use my kiln for the next one and do it exactly at the temp I want.
 
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