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
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.
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.
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:
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:
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.
High carbon, tungsten-alloyed forging steels see consistent use in Japanese knives with steels like the Hitachi Blue series and Takefu V-Toku steels. These steels differentiate themselves from many other knife steels due to their use of tungsten alloying, but not for providing hot hardness like in high speed steels, but for wear resistance. Tungsten-alloyed steels are as old as tool steels themselves, as I covered in an earlier post: The First Tool Steel. However, simple tungsten-alloyed steels have been on their way out in the USA since at least the early 60’s [1]. The tungsten added to the steels leads to the formation of very hard tungsten carbides for steels that can be as wear resistant as air hardening steels like D2 or M2 but with the ability to normalize and anneal the steels without precise temperature control.
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]:
The steel largely recognized as being the “first tool steel” was developed by Robert Forester Mushet, a British metallurgist, in 1868 [1]. Mushet improved the Bessemer steelmaking process through the addition of a small amount of manganese [1]. Later Mushet was experimenting with various additions of elements and discovered that one of his bars of steel had become fully hard despite not being quenched. This was called a “self-hardening” and later “air-hardening” steel because it could be fully hardened in air rather than requiring a water or even oil quench. The reason for the ability to self-harden is due to the property of hardenability, which I have covered in a Bladeforums post [2]. Hardenability is essentially the property of how slowly a steel can be cooled from the hardening temperature while still achieving a hard martensitic microstructure rather than a soft ferrite-cementite microstructure. This steel was high in tungsten and manganese, and it is sometimes erroneously reported that it was the tungsten that gave it the high hardenability; however, it was primarily the manganese that gave it the ability to harden in air, as tungsten adds little to hardenability [3].
