A8 mod testing

A8M - there is an increase of toughness peak at around 620F, I will also post result of A8MHi(ran out of samples for other A8MC1 & A8MC2) for 500F and 600F tempered.

In practice (per given/standard ht), I don't think there is a noticeable diff in toughness between 5%Cr A8 and 8%Cr A8M. Hence no brainer to opt for 8%Cr higher corrosion resistant. Now, if the diff is says 1%Si to 1.8%Si, I am quite certain shock toughness would drastically increase but inverse for yield strength.

Relevancy in knife world: Charpy notched test has limited extrapolate applicability: long blade spine fulcrum impact (sword breaker), baton wood using tip while hammer in front (or at) sharp/crease plunge line. Basically tensional/stretching(at notched/stress-riser) force catastrophically tear/split the blade.
 
BluntCut MetalWorks said:
A8M - there is an increase of toughness peak at around 620F, I will also post result of A8MHi(ran out of samples for other A8MC1 & A8MC2) for 500F and 600F tempered.

In practice (per given/standard ht), I don't think there is a noticeable diff in toughness between 5%Cr A8 and 8%Cr A8M. Hence no brainer to opt for 8%Cr higher corrosion resistant. Now, if the diff is says 1%Si to 1.8%Si, I am quite certain shock toughness would drastically increase but inverse for yield strength.

Relevancy in knife world: Charpy notched test has limited extrapolate applicability: long blade spine fulcrum impact (sword breaker), baton wood using tip while hammer in front (or at) sharp/crease plunge line. Basically tensional/stretching(at notched/stress-riser) force catastrophically tear/split the blade.
Click to expand...
So, from the steels you’ve tested, what’s the toughest steel to make the toughest knife?
 
hugofeynman said:
So, from the steels you’ve tested, what’s the toughest steel to make the toughest knife?
Click to expand...
Let's add "61rc" qualifier to your question.
Obviously this knife should have high edge & structural stability (support high stress elastic load) and wide strain axis (plastic), in order to support high load of easy-abusive edge & frame interactions... yep, steel recommendation could just be another step into useless generalization/ideal w/o full context of usage & relevant criteria... nevertheless
With public ht protocol or services: 80CrV2 follow by 52100, 8670

rodriguezryan14 said:
.. I’m waiting on some cpm1v , and I’m trying to get some asp2012
Click to expand...
1v spec didn't show any Si, so I wonder how well it handle impact/shock load. 3V has 0.8%Si .
 
300F tempered RC | Ft-Lb:
A8MC1: 61rc | 2.3
A8MC2: 62 | 0.6
A8MHi: 63 | 0.4
3VC: 63 | 0.8
3VHi: 64 | 0.4
Aebl: 64 | 0.7
80CrV2: 63.5+ | ~0.5

350F tempered
A8MC1: 60rc | 2.7
A8MC2: 61 | 1.4
A8MHi: 61.5 | 1.0
3VC: 62 | 1.3
3VHi: 62.5 | 0.7
Aebl: 62 | 0.8
80CrV2: 62.5 | 2.8

400F tempered
A8MC1: 59 | 3.2
A8MC2: 60 | 2.4
A8MHi: 60 | 1.7
3VC: 61 | 1.6
3VHi: 61 | 0.4
Aebl: 61 | 0.6
80CrV2: 61 | 3.6

500F tempered
A8MHi: 59.5 | 1.8
3VHi: 60 | 1.8
Aebl: 60 | 1.1

600F tempered
A8MHi: 58.5 | 2.5
3VHi: 59 | 2.6
Aebl: 58.5 | 1.3
 
BluntCut MetalWorks said:
Let's add "61rc" qualifier to your question.
Obviously this knife should have high edge & structural stability (support high stress elastic load) and wide strain axis (plastic), in order to support high load of easy-abusive edge & frame interactions... yep, steel recommendation could just be another step into useless generalization/ideal w/o full context of usage & relevant criteria... nevertheless
With public ht protocol or services: 80CrV2 follow by 52100, 8670


1v spec didn't show any Si, so I wonder how well it handle impact/shock load. 3V has 0.8%Si .
Click to expand...

So, in your opinion, Si is the most important element for toughness? And what about Ni?
 
hugofeynman said:
Those steels look awesome on paper!!!! Asp2012 it’s probably the toughest pm steel in existence. Almost same toughness of H13, but at a better hardness.
Click to expand...
Toughness is very similar to cpm1v. It just has a cobalt addition! 1v isn’t far off from h13. And asp2012 is a particle steel! I’d like to test it if I can get some. The plan is to get some for me and Larrin to test!
 
BluntCut MetalWorks said:
Let's add "61rc" qualifier to your question.
Obviously this knife should have high edge & structural stability (support high stress elastic load) and wide strain axis (plastic), in order to support high load of easy-abusive edge & frame interactions... yep, steel recommendation could just be another step into useless generalization/ideal w/o full context of usage & relevant criteria... nevertheless
With public ht protocol or services: 80CrV2 follow by 52100, 8670


1v spec didn't show any Si, so I wonder how well it handle impact/shock load. 3V has 0.8%Si .
Click to expand...
According to Scott gossman from some older testing, he said it was insanely tough! I’ll know more when i can get some in hand! This is raw toughness though, not necessarily edge strength. It’s more of a malleable steel like A8. Basically unbreakable, but can roll and misalign the edge more easily than some other steels!
Out of curiosity, these tests you’re doing are similar to charpy tests then, correct? These are break tests? Or edge tests?
 
rodriguezryan14 said:
According to Scott gossman from some older testing, he said it was insanely tough! I’ll know more when i can get some in hand! This is raw toughness though,
Click to expand...
Right, # is more/less area under stress/strain curve.
rodriguezryan14 said:
not necessarily edge strength. It’s more of a malleable steel like A8. Basically unbreakable, but can roll and misalign the edge more easily than some other steels!
Click to expand...

rodriguezryan14 said:
vertical impact tester.JPG
Out of curiosity, these tests you’re doing are similar to charpy tests then, correct? These are break tests? Or edge tests?
Click to expand...
There is elastic/yield strength (apex preservation) and plastic region with fracture beyond that. e.g. a low yield strength and wide plastic = mushy edge, so although a8m # might look great compare to 3V, without elasticity region (height and width of strain/deflection) one don't know which one offers better edge stability in a well-defined particular usage.
hugofeynman said:
So, in your opinion, Si is the most important element for toughness? And what about Ni?
Click to expand...
In this context (Cr vs Si, similar C & other elems in solution), Si has stronger aust stabilizing affect.

---------
Logical outcome is: when a material offers high performance/value ratio (bucketize in sectors/fields), products will emerge and eventually capture large % of sector/field market.

Axe market for example: A8,A2,A8M,1V,3V,T1,Aebl,etc... axes are virtually non-existence, even for racing/competition bits where win disregard cost. BCMW context = will test axes in 1095, O1, .. bits with 15 to 17 bevel gauge degrees (inclusive angle), where apex near/at center of hole, chopping green+season clear+knotted woods. This is where both edge and bulk strength/stability are required to pass tests.
 
BluntCut MetalWorks said:
300F tempered RC | Ft-Lb:
A8MC1: 61rc | 2.3
A8MC2: 62 | 0.6
A8MHi: 63 | 0.4
3VC: 63 | 0.8
3VHi: 64 | 0.4
Aebl: 64 | 0.7
80CrV2: 63.5+ | ~0.5

350F tempered
A8MC1: 60rc | 2.7
A8MC2: 61 | 1.4
A8MHi: 61.5 | 1.0
3VC: 62 | 1.3
3VHi: 62.5 | 0.7
Aebl: 62 | 0.8
80CrV2: 62.5 | 2.8

400F tempered
A8MC1: 59 | 3.2
A8MC2: 60 | 2.4
A8MHi: 60 | 1.7
3VC: 61 | 1.6
3VHi: 61 | 0.4
Aebl: 61 | 0.6
80CrV2: 61 | 3.6

500F tempered
A8MHi: 59.5 | 1.8
3VHi: 60 | 1.8
Aebl: 60 | 1.1

600F tempered
A8MHi: 58.5 | 2.5
3VHi: 59 | 2.6
Aebl: 58.5 | 1.3
Click to expand...

Much Appreciated for sharing.

Very intresting results.

What is still strange for me that AKS protocols have hardening temp from 950-1037, Bestar gives a range from 1020-1050, Bohler K329 gives a range from 1000-1020, or 1020-1040 with Air quench. Its of course exact content and microstructure dependent, but thats still a fairly broad range. The common range for A8Mod type steel is 1020-1040 1870-1905 Fahrenheit.

The other topic here is edge stability. I would assume that faster quenching rate would result in lower level of retained austenite amd higher strength ad the edge. Did you use plate quench with SS foil? I was thinking about cutting the pouch and oil quench to expedite cooling, followed by triple Dry Ice Sub Zero.

As it was mentioned here earlier its a highly mallable steel, and even though toughness is great, for thinner edges or steeper angles the edge stability is highly important.
 
Zozo*HC* said:
Much Appreciated for sharing.

Very intresting results.

What is still strange for me that AKS protocols have hardening temp from 950-1037, Bestar gives a range from 1020-1050, Bohler K329 gives a range from 1000-1020, or 1020-1040 with Air quench. Its of course exact content and microstructure dependent, but thats still a fairly broad range. The common range for A8Mod type steel is 1020-1040 1870-1905 Fahrenheit.
Click to expand...
I am guessing that, AKS tried & took WalterMetals A8 HT protocol, where slow ramp = slowly release Carbon to solution, then soak 30 minutes at a tad lower aust temp. This is just a conservative protocol which support simple to complex work piece. Well, a blade is super simple so slow ramp is unnecessary (inefficient use of time, especially doing small batch and expose longer risk of decarb in leaky ss foil wrap). A8Mod has 8-8.5%Cr so a tad higher aust to release ~same % of C into solution compare to 5% A8. Bohler K329 tempering chart is quite good, where I did get 62rc using 1875/40min -40C (so probably can get another 0.5 to 1rc using dry-ice or LN2 respectively).
Zozo*HC* said:
The other topic here is edge stability. I would assume that faster quenching rate would result in lower level of retained austenite
Click to expand...
Sometime yes, sometime some where in between and sometime it is the opposite. One can trial and errors or see the crystal transformation/kinetic in your mind then manipulate/steer the transformation.
Zozo*HC* said:
amd higher strength ad the edge. Did you use plate quench with SS foil?
Click to expand...
Yes, quenched in foil
Zozo*HC* said:
I was thinking about cutting the pouch and oil quench to expedite cooling,
Click to expand...
See 'assume'
Zozo*HC* said:
followed by triple Dry Ice Sub Zero.

As it was mentioned here earlier its a highly mallable steel, and even though toughness is great, for thinner edges or steeper angles the edge stability is highly important.
Click to expand...
Design/tailor edge according to your set/goal Yield Point (elastic limit in stress strain curve of hardened steel). Mallable/ductile/plastic/fracture is after apex yielded ... so don't yield too easily (with low stress and or narrow elastic region).
easier to see using a good enough img found in search - https://cdn1.byjus.com/wp-content/uploads/2019/02/Stress-Strain-Graph2.png
 
BluntCut MetalWorks said:
300F tempered RC | Ft-Lb:
A8MC1: 61rc | 2.3
A8MC2: 62 | 0.6
A8MHi: 63 | 0.4
3VC: 63 | 0.8
3VHi: 64 | 0.4
Aebl: 64 | 0.7
80CrV2: 63.5+ | ~0.5

350F tempered
A8MC1: 60rc | 2.7
A8MC2: 61 | 1.4
A8MHi: 61.5 | 1.0
3VC: 62 | 1.3
3VHi: 62.5 | 0.7
Aebl: 62 | 0.8
80CrV2: 62.5 | 2.8

400F tempered
A8MC1: 59 | 3.2
A8MC2: 60 | 2.4
A8MHi: 60 | 1.7
3VC: 61 | 1.6
3VHi: 61 | 0.4
Aebl: 61 | 0.6
80CrV2: 61 | 3.6

500F tempered
A8MHi: 59.5 | 1.8
3VHi: 60 | 1.8
Aebl: 60 | 1.1

600F tempered
A8MHi: 58.5 | 2.5
3VHi: 59 | 2.6
Aebl: 58.5 | 1.3
Click to expand...
Thank you for doing this! I have one question. You list 3VC and 3VHi with the same Aus. temperature in your original post (1950F). Was this was a typo?
 
You must log in or register to reply here.
Back
Top