Category: Steel and Knife Properties
2 thoughts on “Steel and Knife Properties”
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How Chipping of Edges Happens at a Microscopic Level
Thanks to Warren Krywko, Joseph Cannell, and Timothy Thomas for becoming Knife Steel Nerds Patreon supporters! Your contributions will help fund more research on knife steels.
To discuss chipping we have to start with fracture mechanics of materials, and in this case steel. Chipping itself is just fracture, so by definition resistance to chipping is controlled by toughness. Unfortunately there are many definitions of toughness. I covered one definition of toughness in the article on spider silk, which is the area underneath the stress-strain curve:
Is Spider Silk Stronger than Steel?
This article was discussed on the very popular Skeptic’ s Guide to the Universe podcast: https://www.theskepticsguide.org/podcast/sgu/670
Nearly a year later they briefly discussed the article as being very impactful in correcting some common knowledge they had always believed: https://www.theskepticsguide.org/podcast/sgu/714
What Makes Quenched Steel so Hard?
Update: I have started a Patreon page to fund research projects which you can read about here – http://knifesteelnerds.com/how-you-can-help/
To harden steel you heat it up to high temperature to form a phase called austenite, followed by rapid quenching to make a very strong phase called martensite. Hardness is a measure of strength. I covered the process of austenite formation in the following post: Austenitizing Part 1. To summarize that post:
Cru Forge V – Toughness testing, Processing, and Background
Cru Forge V was developed by Crucible for those who forge their steel for knives [1]. It was developed shortly before Crucible’s bankruptcy and is reported to have been tested with the help of knifemakers Howard Clark and Dan Farr and that the code name prior to its official name was 1086V [2]. The steel is not listed anywhere on Crucible’s website and does not appear to be in production any longer, but as of March 2018 is still available from some third party steel sellers [3][4][5]. The steel has the following composition [1]:
How Does Grain Refinement Lead to Improved Properties?
Update 6/21/2018: A new journal article has been released on the effect of grain size which is very interesting. I have added a brief summary of it at the bottom of this article.
In my posts on austenitizing I described parameters of heat treating to keep grain size as small as possible and therefore improve strength and toughness [1-3]. It is very difficult to improve both strength and toughness at the same time, usually increasing one decreases the other. By what mechanism does grain refinement improve both?
Why Doesn’t Heat Treating Affect Steel “Flex?”
One concept that can be difficult to understand intuitively is that the hardness or strength of steel does not change its stiffness. Meaning, “flexing” steel without permanently bending it is not changed by its hardness. I have heard many people swear up and down that they can tell a difference, so I found a great Youtube video that illustrates this [1]:
Those photos and drawings will help people understand ! Orientation – I was curious about what Crucible does with that .Their CPM goes to Niagra Metals for rolling and they cross roll the steel. Cut into squares and rolled alternating direction to minimize directional properties. I think Matt Gregory found that in his visit.
It would be interesting to test the transverse toughness of those steels for sure.