Category: Steels
4 thoughts on “Steels”
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Silicon Additions for Improving Steel Toughness
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High Toughness Steels
There are a series of shock resisting steel designed for high toughness (see this article to learn about toughness). A popular one is S7, an air hardening steel that can reach relatively high hardness. Another steel in the “S” series, S5, is reported to be even tougher [1][2][3][4]:
New Steel Analysis – Damasteel N11X and Damacore DC18N
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N11X and Damacore DC18N
Last month I released an article about nitrogen-alloyed knife steels. After I posted the article I was informed about a new Damasteel product that includes a nitrogen-alloyed stainless steel as the core in a san-mai damascus steel product. At the time there was no information on the core steel other than its name: Damacore DC18N refers to a product with a core of “N11X” nitrogen steel and has san-mai damascus sides of RWL34 and PMC27 (their standard damascus mix without a core steel). Damasteel has recently released a datasheet for the new product which has provided more information: http://damasteel.se/wp-content/uploads/2018/06/Data-Sheet-Martensitic-Damacore-Final-Version.pdf
Super Steels vs Regular Knife Steels
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Super Steel
I see frequent references to “super steel” online, and I was curious about how long that terminology has been around. I did searches on bladeforums as it is one of the oldest knife forums. The number of references to “super steel” has increased over time, but so have the number of posts on bladeforums. I saw how many references to “super steel” there were in each year, and then as a proxy to how many posts there were on bladeforums I did a search for “154” and saw how many references there were each year. Google tops out at 200 results but at that point the dataset was big enough to get an idea:
Nitrogen-Alloyed Knife Steels
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In previous posts I have written about the process by which steel is hardened. The steel is heated to a high temperature phase called austenite, where carbides are dissolved and carbon goes into solution in the austenite. During rapid quenching the carbon is trapped between the iron atoms and a phase called martensite is formed. Martensite gains its high hardness from the distortions to the atomic structure that come from carbon in between the atoms.
Carbon vs Stainless Steel in Knives
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Ranking the Steel Ranking Articles
Note: I now have a steel ratings article of my own, read it here: Knife Steels Rated by a Metallurgist
Intro
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What is Powder Metallurgy?
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Conventional Casting
Five Myths About Damascus Steel
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What is Damascus Steel?
There are two major steel types that are called Damascus:
1. Crucible, or Wootz, steel was first produced in India and Central Asia and produced into swords anciently from at least the 3rd century AD [1]. It is made by producing small ingots of high carbon steel that are then forged and thermal cycled in a specific manner to lead to carbide bands that produce the final pattern when the steel is etched [2][3]:
Steel History – The First Stainless Steel was for Knives
Update 7/23/2018: I added a small piece of new information on the development of 440C steel to the article.
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The writing of this article was made much easier due to the existence of The History of Stainless Steel by Harold Cobb [1]. If you want more information on the history of stainless and the people who developed it, check out the book.
How Much More Chromium Does D2 Need to be Stainless?
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Some materials like aluminum form a passive oxide layer that prevents further corrosion. Steel is not one of those materials. Instead, steel forms iron oxide, or rust, that doesn’t protect the underlying iron and flakes off leading to further corrosion. However, when sufficient chromium is added then a chromium oxide passive layer forms which protects the steel from corrosion in a similar way to a metal like aluminum with its own aluminum oxide layer. A simple schematic diagram shows the passive film vs rust [1]:
Thanks for what you are doing. There is so much misinformation, hyperbole, and exaggeration being presented as fact on the internet regarding knife blade steel. I felt like the skies cleared when I discovered your site. I really appreciate your science-based approach to demystify so many issues.
Thanks!
Can you tell me about AR-RPM9 please?
Thanks,
Mine S
I’ve only written about AR-RPM9 in an article exclusive to the Knife Steel Nerds Patreon.