Weil es ein so interessantes Thema ist, hier noch etwas Lesestoff:
Larrins Ziel war es, im Angesicht von rostfähigen Stählen - wie z.B. CPM 4V oder CPM CruWear - die wegen ihrer guten Ausgewogenheit von Schnitthaltigkeit und Zähigkeit strahlen, einen hoch härtbaren, rostträgen Stahl mit ebensolchen Eigenschaften zu designen. Den es bisher nicht gibt.
Im Ergebnis zeigt der CPM MagnaCut genau diese Ausgewogenheit.
Nach Zielvorgabe sollte der Anteil an Chromkarbiden möglichst gering sein. Er ist gleich Null! Der gesamte Chromanteil steht frei in der Grundmasse zum Rostschutz zur Verfügung. Dadurch bedingt ist der Stahl in unerwartet hohem Maße rostträge.
Zudem ist er bis 65 HRC härtbar. Und er ist sehr feinkörnig, was der guten Bearbeitbarkeit und Schärfbarkeit entgegenkommt. Das wurde erreicht durch die - neben Vanadium - geringe Hinzulegierung des aggressiven Karbidbildners Niobium, der sehr kleine, harte Karbide bildet und zudem ein Anwachsen der Korngröße in der Grundmasse bremst.
Wenn man eine der erreichten Eigenschaften als vernachlässigbar ansieht, gibt es natürlich diverse Stähle, die man in Betracht ziehen kann. Ist Rostträgheit nicht von sonderlichem Belang, kann man CPM 4V nehmen, M390 ist gut schnitthaltig und rostträge aber wenig zäh, LC200N ist sehr rostträge und zäh aber nicht sonderlich schnitthaltig usw.
Wenn es aber um die Ausgewogenheit von Schnitthaltigkeit, Zähigkeit und Rostträgheit (magisches Dreieck) bei hoher Härtbarkeit geht - und genau das war der Plan - hat CPM MagnaCut ein Alleinstellungsmerkmal …
"CPM MagnaCut is the result of my passion for knives and steel. I used a new approach to stainless tool steel design to eliminate chromium carbides from the microstructure. This led to a combination of properties which is better than previous stainless knife steels, and has similar toughness and edge retention to non-stainless steels like CPM-CruWear, CPM-4V, and Vanadis 4 Extra. The corrosion resistance was also excellent, even better than I was expecting, which means that the hardness-corrosion resistance balance of MagnaCut is very impressive, with achievable hardness being 64+ Rc and corrosion resistance being even better than steels like S110V, S45VN, and M390.“
Die folgende Würdigung hat Deadboxhero (Shawn Houston / Big Brown Bear) - der einige Messer aus CPM MagnaCut gemacht und getestet hat - im
Spyderco-Forum abgesetzt:
„ … it was not thought to be possible to have a stainless 4v with finer carbides than even 4v but Dr Larrin was able to do exactly that by hacking the steel code and balancing the chemistry out perfectly to achieve this which is an impressive display of metallurgical prowless and passion.
So far the MagnaCut is pretty overpowered. What makes it so remarkable is it represents taking the best atributes of midrange carbon PM tool steels and mid range PM stainless and putting them together with seemingly no disadvantages I've yet to experience.
MagnaCut will not out cut 10v, Maxamet, or s90v, s125v etc. I'm embarrassed to say this as It should be obvious that those are not the steels to compare it too but everyone is starting from different places with geeking out on this stuff so I have to say it before someone asks.
I couldn't believe it had slightly finer carbides than 4v but it's thanks to the niobium and nitrogen that's neatly balanced with the other elements to produce the desired effect that is keeping the carbides slightly finer than 4v which is very impressive.
Everything one sees in the chemistry is perfectly balanced, all the chromium carbides are dissolved leaving only fine vanadium and niobium rich carbides. All the chromium needed to make the steel stainless is in solution nothing more, nothing less. It is also the only steel I know that seems to combat retained austenite. Very elegant design
The edge comes up very crisp with a sneaky little bite of subtle aggression at the end. Deburrs noticable well, I enjoyed it both at 62.4rc all the way up to 65.5 rc. I even made some in the 64rc range which is also a nice sweet spot.
At higher hardness the edge deburred better and got crisper. The higher hardeness edge has more strength but less shock resistance yet that edge is also less prone to rolling/blunting in use with very thin geometry. At 62-63rc (with proper microstructure from good heat treatment) I was very impressed with the edge durability. Personally, I haven't seen this kind of durability in a PM stainless grade.
I handsanded MagnaCut at 65.5rc and Zwear (ZAPP Cruwear) at 65rc but noticed the MagnaCut finished better with more ease despite being harder with more hard carbide, I'm guessing it's thanks to the finer carbides. In rope cut testing the MagnaCut also had a slightly lower BESS score with
The same amount of fixed cuts on 3/4 Manilla Rope meaning it stayed sharper with the same amount of cuts (although the MagnaCut was 0.5rc harder)
Zwear (Cruwear) has more carbide volume but it has chromium carbides mixed in with Vanadium rich carbides. Chromium carbides are not as effective at increasing wear resistance as Vanadium and Niobium due to the lower hardness of chromium carbide.“
R’n‘R