Anyone else sick of Magnacut already…

Sick of Magna?

  • Fo shizzle, Magna overblown dawg

    Votes: 37 25.0%

  • Nah I luvs it

    Votes: 115 77.7%
  • Total voters
    148
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DeadboxHero said:
Well, MagnaCut will be able to take advantage of higher strength at the edge to support lower angles with better resistance to deformation. Vanax will have a higher total carbonitride volume however the hardness HRC is limited. Vanax will have a higher volume of softer phase retained austenite in the matrix even with cryogenic processing which is detrimental to edge strength and apexing.

Lower edge angles in general will cut longer at a trade off with raw durability.

MagnaCut has fine carbonitrides at a lower volume and good toughness and working hardness range.

All of those features can be more advantageous for lower edge angles.

We can model this by graphing data from the Predicative CATRA formula below.

TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 5.0*Fe3C(%) + 11.2*CrC(%) + 14.6*CrVC(%) + 26.2*MC(%) + 9.5*M6C(%) + 20.9*MN(%) + 19.4*CrN(%) [1]



EsgNyXZ.png

Figure 1. Same edge angle 15°dps

DEQzLSK.png

Figure 2. MagnaCut with a 14° dps edge angle(-1°dps lower than on Vanax)

liAsF24.png

Figure 3. MagnaCut with a 13°dps edge vs a 15°dps edge on Vanax.

As Roman Landes has said "geometry cuts"


[1]https://knifesteelnerds.com/2018/11/19/steel-edge-retention/
Click to expand...
So you're comparing Magnacut at 13 and 14 dps to Vanax at 15 dps, so it would make sense that that Magnacut would come out on top. Presumably that's on the theory that Vanax at 60-61 hrc wouldn't hold up at sub-15 dps edge angles. But I wonder if that would actually prove out on a Catra test? I wouldn't expect it to hold up AS well as the 64 hrc Magnacut, but I would expect it to perform better than 15 dps Vanax.
 
Blade Lab said:
So you're comparing Magnacut at 13 and 14 dps to Vanax at 15 dps, so it would make sense that that Magnacut would come out on top.
Click to expand...
You might have missed it, but
If you look at the graphs in my post, you'll see there are 3 graphs.

15 vs 15
15 vs 14
15 vs 13

Blade Lab said:
Presumably that's on the theory that Vanax at 60-61 hrc wouldn't hold up at sub-15 dps edge angles. But I wonder if that would actually prove out on a Catra test? I wouldn't expect it to hold up AS well as the 64 hrc Magnacut, but I would expect it to perform better than 15 dps Vanax.
Click to expand...

A true, flat 15° per side that is actually confirmed on a laser goniometer is already pretty extreme.

Edge durability doesn't start until +20dps even in very tough steels.

75R7VHt.png
 
DeadboxHero said:
Well, MagnaCut will be able to take advantage of higher strength at the edge to support lower angles with better resistance to deformation. Vanax will have a higher total carbonitride volume however the hardness HRC is limited. Vanax will have a higher volume of softer phase retained austenite in the matrix even with cryogenic processing which is detrimental to edge strength and apexing.

Lower edge angles in general will cut longer at a trade off with raw durability.

MagnaCut has fine carbonitrides at a lower volume and good toughness and working hardness range.

All of those features can be more advantageous for lower edge angles.

We can model this by graphing data from the Predicative CATRA formula below.

TCC (mm) = -157 + 15.8*Hardness (Rc) – 17.8*EdgeAngle(°) + 5.0*Fe3C(%) + 11.2*CrC(%) + 14.6*CrVC(%) + 26.2*MC(%) + 9.5*M6C(%) + 20.9*MN(%) + 19.4*CrN(%) [1]



EsgNyXZ.png

Figure 1. Same edge angle 15°dps

DEQzLSK.png

Figure 2. MagnaCut with a 14° dps edge angle(-1°dps lower than on Vanax)

liAsF24.png

Figure 3. MagnaCut with a 13°dps edge vs a 15°dps edge on Vanax.

As Roman Landes has said "geometry cuts"


[1]https://knifesteelnerds.com/2018/11/19/steel-edge-retention/
Click to expand...
This is an issue that I have become aware of recently. Your graphs indicate that, going from 65 to 61 HRC, Magnacut suffers a 10% decrease in cutting longevity. So what’s the big harm in turning out a Magnacut knife at 61 or M390 at 60? I mean who is really going to miss that extra 10% of cutting endurance? How long does it take you to dull a knife, unless you’re cutting shingles?
 
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LarryG said:
This is an issue that I have become aware of recently. Your graphs indicate that, going from 65 to 61 HRC, Magnacut suffers a 10% decrease in cutting longevity. So what’s the big harm in turning out a Magnacut knife at 61 or M390 at 60? I mean who is really going to miss that extra 10% of cutting power? How long does it take you to dull a knife, unless you’re cutting shingles?
Click to expand...



It's explained in this video.

"Modes of sharpness loss"
 
Looking at Larrin's data, MagnaCut has about 17 ft-lbs of toughness at 61 Rc. It gets 505 TCC in cutting tests of abrasive wear resistance. That high level of toughness appeals to me. It makes MagnaCut more resistant to breaking and chipping than any other powder stainless steel.

But a large segment of the market seems to want MC run much harder -- more like 64 Rc.

At 64 Rc, MC has about 12 ft-lbs of toughness and gets 550 TCC.

The steel I'm most familiar with is Vanax -- as a user, not an expert. It's been my hard-use EDC for years, including lots of chopping that has ruined blades made out of other steels. Vanax is also my daily-use chef's knife -- which has a very thin blade made out of 0.065 inch stock.

At 60ish Rc, Vanax has about 12 ft-lbs of toughness and gets 545 TCC. At that hardness, MC is a lot tougher, but has a little less abrasive wear resistance. (These are Larrin's numbers.)

When MC is taken up to 64 Rc, it drops to about the same toughness as the softer Vanax, with almost the same abrasive wear resistance.

The idea that MC at 64 Rc can be run thinner and thereby cut longer is true only for abrasive wear tests. In the real world, edges degrade from damage, not just wear. Edge stability refers to how well knife edges resist chipping/breaking/cracking and denting/rolling/bending. This from Larrin's website: "With thin, low angle edges the possibility of edge rolling and/or chipping is much stronger than the possibility of edge wear."

When you made an edge steel harder and more acute and reduce its toughness, you make it more vulnerable to chipping, breaking and cracking.

At 61 Rc, MC is much more resistant to that kind of damage than Vanax at that same hardness. But if you take MC up to 64 Rc and thin out the edge and made the edge angle more acute, you now make the MC edge more vulnerable to chipping, breaking and cracking than the Vanax blade.

MC is a great steel and a brilliant advance in metallurgy. But hardness has a strong effect on knife performance. MC at 61 Rc and at 64 Rc do not perform the same. How you use the knife will depend on what hardness works best for you.
 
I for one would much rather it at 64 than 61. Especially since it seems it's has the toughness and strength for that. It would make a good all purpose blade that would make me willing to buy more knives. I have been very happy with my k390 around 64 and my 15v at I think 65. I have seen no chipping whatsoever and I've used them well, not babied. So to me I'd gain nothing to go softer and would actually be giving up something in strength and resistance to deformation. I think toughness is very overrated in blades for folders. Either way isn't magnacut even at 65 tougher than the current "standard" of s30v at its typical 59 or so? Yes.
 
You didn't read my post. I'm talking about the loss of toughness.

My Rex 121 knife, with 0.007 inch BTE width, is super hard at 70 Rc. It will resist deformation better than any MC knife. But I can use it only for opening packages, because while it has amazing strength and ability to resist deformation, it is highly vulnerable to breaking,
 
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