Let me start by saying that I've spent a lot of money at blade HQ and continue to be a customer of theirs. I should also say that I'm not a steel expert and I should warn you that this is a deep rabbit hole from which there's no return.
When I was brand new to knives, I looked at their steel rankings a lot. They should be applauded for even making one because it's not easy.
I feel that their rankings are due for an update. I disagree with how they've ranked some steels and many new and important steels are missing.
Its very difficult to rank steels in a linear way because there's more than one way to look at edge retention, there's different kinds of edge retention, and there's different kinds of toughness. There's also different definitions of what "dull" means. Making it worse, the media being cut will dramatically alter the results. Cardboard specifically levels the playing field a bit and "budget" steels like 14c28n and AUS-8, in controlled cut tests, deliver results similar to or better than S30V, S35VN, M390, 20CV, and CTS-204P.
Some steels like M390/20CV are held in high regard because of how they balance different attributes.
Steels like S110V are ranked high because of "wear resistance" which is a component of edge retention... but it's just one component. In some cases the strength at the apex matters a lot.
The standardized equipment used in the industry to test edge retention is called a CATRA machine. Its results also have to be taken with a grain of salt, because of the media being cut, as well as the high level of dullness the machine achieves. Its far beyond where most people would take an edge in terms of dullness. With that being said, CATRA tests are a critically valuable datapoint and are a good measure of wear resistance. We need more of them.
The same is true for rope and cardboard cut tests on YouTube.
As previously mentioned above, Larrin, an actual expert on this subject has a CATRA machine and he just published test results for 48 different steels on
www.knifesteelnerds.com
Its best to not look at one set of tests or rankings versus another as being correct or incorrect. They're all guidelines and data points and have to be taken in context.
The variables introduced by the end user will make the largest difference on edge performance.
Three primary categories make up "edge retention"
1. Edge geometry. This primarily is set by the end user with the edge angle and grit finish.
2. Chemical composition or the ingredients of the alloy, are standardized for each steel but there's some variation, especially with certain steels.
3. Rockwell Hardness (HRC) The chemical composition and the heat treat/temper will determine the final HRC. An optimal heat treat process is determined based on the steel composition and the results desired
Higher hardness gives more strength at the apex of the edge. The wear resistance of softer steels count for nothing if you're rolling, blunting, or chipping your edge.
Some steels are very strong at high hardness, which is why the new high end non stainless tool steels are so important.
Hardness is critically important and quickly becomes the most important, but the heat treat could be botched leaving the desired HRC but the wrong chemistry in the alloy. Obviously, problems with composition creates problems with the final result as well. HRC is only important when everything else is correct.
Even when all of the above is perfect, the end user can easily botch the sharpening in various ways, killing the performance of the edge.
Additionally the physical geometry of the blade itself will dramatically alter cutting performance in all kinds of ways. With bad geometry, the edge retention wont matter.
