Master Member KnifeNut!
12-25-06 17:57.38 - Post#1114907
In response to Larrin
I tested a steel a couple years ago with very similar qualities. On paper it looked great, achieved Rc60+ with microdispersed carbides on the order <0.1 microns, took an amazing edge, exceeded 154CM and 440C on CATRA edge holding tests, and...
...Bent like a pretzel on hard impacts. I have a photo of identical edges on it and 154CM after cutting 8d nails. Plastic deformation.
CPM-1V has a somewhat similar physical composition, and looks great on paper. Same problem, nice microstructure, reasonably good hardness, tough, but weak.
I think there's a threshold of carbide content necessary to support a knife edge, especially a fine edge and particularly one which might experience even moderate impacts. CPM-3V is right on the cusp of this problem. It's failure mode is minor plastic deformation with very hard impacts on fine edges. To put some dimensions on that, I've had a blade in 3V that cut through 3"+ of beef leg bone, suffering about a 1/8" long by ~1/32 - 1/64" deep flat spot at the point of impact. I had another 3V blade a Rc61 bent to 90 degrees 4 times before it broke. Great performance by most measures, but it would be the wrong steel to use in the Professional Cutting Competitions, because edge deformation is a disqualifying condition. At the same time, the steel would pass the ABS Journeyman blade performance tests.
The issue of weaker edges is that while they can under controlled conditions seem to hold up reasonably well in edge retention, it doesn't take much abuse to roll and render the edge dull or worse still bend the edge and make the blade useless.
You can take almost any steel, make a knife of it, and use tests that will portray it in a favorable light. In fact it might be that a steel is ideal for a narrow range of applications, but extrapolation from those tests to broader utility is simply invalid. The problem with many of these discussions is that label are often measured in broad strokes as in "steel composition" for "knife edges" in "cutting tests" and "edge retention" and "tough", without defining the range or scope of the conditions and applications.
That kind of dialog that takes place on another forum where intelligent discussion is smothered in a deluge of technical-sounding BS. To make this clear, I am NOT an anti-science nut, and I most certainly do respect well-designed scientific testing and statically valid conclusions. BUT, when the dialog is comprised of loosely connected sets of facts from several unrelated sources, combined with undocumented empirical results to form meaningful conclusions, it troubles me.
And to make clear my position on the issue of scientific integrity, I spent a good number of years (~30) working in the sciences (biomedical), have managed multi-million dollar R&D activities comprised of both engineers and laboratory scientists, and hold eight patents on mechanisms ranging from laboratory tests to analytical instrument designs. I have deep respect for the kind of science that Doc is offering here. I have some issues with connecting it to anecdotal evidence from elsewhere and deciding AEB-L is an excellent knife steel. It might be a great steel, but I'd sure like to see some serious testing before concluding that. I do think it interesting that there aren't more European knifemakers who use it.
It MIGHT, however, be ideal for use with a higher carbide stainless in a stainless damascus. In fact, I know it is.
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