Author: Larrin
Toughness testing – Cru-Wear, Z-Wear, Upper vs Lower temper, Cryo vs No Cryo
Thanks to Paul Hart and James Covington for becoming Knife Steel Nerds Patreon supporters!
I recently completed some toughness tests on samples that were heat treated by knifemaker Warren Krywko. The steel was donated by Chuck Bybee of Alpha Knife Supply. The samples are subsize unnotched charpy specimens with dimensions as specified on the bottom of this page: http://knifesteelnerds.com/how-you-can-help/ If we can get more people to make toughness specimens we can have more comparisons between steels, hardness points, heat treatment parameters, etc. Patreon dollars are for the purpose of paying for machining, shipping, testing, etc. for tests like toughness and CATRA edge retention, so if you are able to contribute that way please visit the Knife Steel Nerds Patreon page.
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:
154CM – Development, Properties, Use in Knives, and Legacy
Update 6/19/18: I have added new toughness numbers from a 1962 publication comparing 440C and 154CM. Go to the bottom of the article to see them. Thanks to Russ Andrews for sending me the article.
Thanks to Sal Glesser, Brian Huegel, Mark Bellou, Timothy A. Johnson, Daemon Lindenmayer, and David Olkovetsky for becoming Knife Steel Nerds Patreon supporters! We reached our goal of funding an edge retention study!
Why There is Cobalt in VG-10
Thanks to Phil Wilson for become a Knife Steel Nerds Patreon supporter. We have now reached our second goal of funding a toughness study! I will start putting together the plan and discussing it with the patrons. Next goal: funding an edge retention study.
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
Reader Question – O1 vs 80CrV2
Larrin,
Someone said austempered o1 would be as tough or tougher then martempered 80crv2. Could you help me wrap my head around that?
I have an affinity for fine grained simple steels, and o1 being precision ground and available in all different sizes is great, but if 80crv2 has a finer grains structure and is tougher I’d be sold. It’s for a run of belt hawks that will be used primarily for woods and hunting duties not destruction tools. But I’d also like to focus on one steel for a while and curious if for small to medium belt knives which you’d recommend? I’ve played with most of the high wear and too steels, but haven’t messed with too many of the high carbon steels as I hated 1095.
What Happens During Tempering of Steel?
Thanks to Shawn Houston and Tyler Christian for becoming Knife Steel Nerds Patreon supporters. We have reached our first goal and therefore I will be interviewing Devin Thomas and posting it as an article to the website.
The Development of High Vanadium Steels, M4, and the First Tool Steels Book
Thanks to Gary Cornell and Devin Thomas for becoming Knife Steel Nerds supporters on Patreon.
Last Time, in Steel History….
When we last left steel history, the first high speed steels had been developed which had led to an explosion in steel development. I covered all of this in The History of the First Tool Steel. A few highlights of that article:
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:
Results of Steel Nerd Quiz
This past week I did a quiz on my site to get a feel for the level of knowledge of my readership (or at least the ones that take quizzes) and of course for fun: Take the Quiz Here.
At the time of writing there are more than 900 responses to the quiz (update: 1000!), which I think is a success. I have performed some analysis of the results of the quiz and so I will go over some of the questions that tripped people up and how I might adjust what I write about on this site based on the responses.