New Magnacut, stained after first use in kitchen

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knifeism said:
By everyone: https://gprivate.com/6crr6



"CPM MagnaCut is a new stainless knife steel designed to be better than anything that has been available before."

Also, and I'm not sure who needs to hear this, but being surprised that something works, is claiming it works.

In terms of staining, it's not better than anything I've ever used, it's worse than everything, to the point I actually need to research stain removers because nothing works.
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Here is the introduction of Magnacut by the designer of the steel. Don't believe ad copy.
knifesteelnerds.com

CPM MagnaCut - The Next Breakthrough in Knife Steel - Knife Steel Nerds

CPM MagnaCut is a new stainless knife steel designed to be better than anything that has been available before. Is it a success?
knifesteelnerds.com knifesteelnerds.com
 
Haven't noticed any discoloration on my Bradford Guardian 3 after cutting meat, tomatoes, fruit -- all acidic material-- maybe because of the stonewash finish. Wouldn't bother me if it did pick up a bit of patina, though.
 
I prefer a nice patina over just a clean look. At any rate, stainless should really be stain less. That's for all "stainless" steels.
 
knifeism said:
"CPM MagnaCut is a new stainless knife steel designed to be better than anything that has been available before."
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knifeism said:
True, but Magnacut is touted as the most stainless steel in the universe
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You don't see how these two statements are different?

Who is the maker?

And, you haven't used anything that would remove a light patina. You need an abrasive, like a polish. The flitz suggsted above is what I use when I need a light abrasive.

I do know who needs to hear this, all stainless steels do stain, just less. Even H1 can develop some cloudiness that clears up with a little flitz.

There is also the matter of manufacturing and/or sharpening contamination. I have had some spots on steels I thought should not (lc2000n, 4116). Flitzed them off and no issues since.

Magnacut is the best steel we've seen at all around edge holding, toughness, and rust resistance. It is not the best at any one of those things.

Your expectations need to be more aligned with reality.
 
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Larrin said:
That is not how it works. In fact it can be easier to get high corrosion resistance with high hardness. In terms of heat treatment the biggest effect is whether they use the high or low tempering regime. The 900F+ tempering temperature leads to worse corrosion resistance with stainless steels but is semi-common. The other major effects are how the steel is finished and whether they effectively clean remaining steel particles from the knife. There is a process called passivation where those free particles can be removed with a weak acid.

Edit: This misunderstanding seems to come from the fact that high corrosion resistance steels can have limited hardness from extra chromium in solution to achieve the corrosion resistance. Therefore LC200N and Vanax max out around 60-61 Rc. However, that is when comparing different steel types, not the same steel with a different heat treatment.
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So are we getting poor tempering down to whatever hardness? Does CRK do their own heat treating? I vastly prefer their 63-64 to anyone else with 62 or lower, but is this saying they are maybe putting out a not as great product???
 
Maximumbob54 said:
So are we getting poor tempering down to whatever hardness? Does CRK do their own heat treating? I vastly prefer their 63-64 to anyone else with 62 or lower, but is this saying they are maybe putting out a not as great product???
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I can’t comment specifically about the temperatures used by CRK. I have two Sebenzas in MagnaCut and neither has shown any staining.
 
knifeism said:
"CPM MagnaCut is a new stainless knife steel designed to be better than anything that has been available before."
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That is the stinger description for Google, you missed the “Is it a success?” question that followed. Meaning the reader is invited to read the article and come to his own conclusions. Of course it does not say or imply that the corrosion resistance is better than any other steel. The corrosion resistance is better than many other knife steels as I showed with the testing in the article.
 
Larrin said:
That is not how it works. In fact it can be easier to get high corrosion resistance with high hardness. In terms of heat treatment the biggest effect is whether they use the high or low tempering regime. The 900F+ tempering temperature leads to worse corrosion resistance with stainless steels but is semi-common. The other major effects are how the steel is finished and whether they effectively clean remaining steel particles from the knife. There is a process called passivation where those free particles can be removed with a weak acid.
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Interesting. On a side note, I have a "stainless" revolver, that started rusting quite a bit, even though I maintained it well. I sent it back to S&W that blasted and re-passivated it (where I learned the term - seems to be routine for guns). No problem since then. Don't know of any knife maker who does it though.
 
Larrin said:
That is the stinger description for Google, you missed the “Is it a success?”
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So what you're saying is the knowledge he displayed was only ... surface level.
 
As promised, proof and pudding (or however that saying goes).

KezcbXu.jpeg


https://imgur.com/K3xUxXD

I don't recall what HRC was achieved for this one, although I believe it was above 62. Again, this light patina only showed up after cutting raw, red meat. No rust or additional coloration after cutting fruit, pickles, limes, and other wet, acidic materials and being put up wet. Frankly, I think a light patina with no rust is an awesome feature (if that's what it really is).
 
Yes, I had Jarod heat treat that knife to 62-63 RC. But I finish my blades to a relatively low satin finish, and that plus the fact that I was not aware of passivation before are almost certainly contributors to enabling surface oxidation. Probably work out differently if my process included going to a high finish with polishing, that has never been a part of my process. I'm not about to start taking stuff to a higher finish, because that will drive my prices past a point I want to charge. However, I have already begun researching passivation as a possible addition to the shop process.
 
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