Hardenability, Quenching

How Fast Do You Have to Quench? Hardenability of Steel

Larrin

Thanks to Richard Patterson, Patrick Guignot, Aaron Lee, and David Richardson for becoming Knife Steel Nerds Patreon supporters!

Hardenability

How fast one must quench steel is controlled by its hardenability. Hardenability is not a measure of how hard a steel can get. Instead it is a measure of how fast you have to quench to achieve max hardness for a given composition. Therefore a steel with 0.2% carbon can have high hardenability without being able to reach a particularly high hardness; the steel can be allowed to cool in air and achieve more or less the same hardness as when it is quenched in water. On the other hand, a steel with very high carbon content that can reach very high hardness can have low hardenability, requiring a water quench to achieve its potential hardness. read more

Edge Retention, Steel and Knife Properties

Can CATRA predict Rope Cutting Performance?

Larrin

Thanks to Fingal Ferguson for becoming a Knife Steel Nerds Patreon supporter!

CATRA Edge Retention Testing

I previously wrote articles about CATRA testing of edges. The CATRA test uses 5% silica-impregnated cardstock which it slices with a fixed stroke length and force. The first article primarily looked at the effect of edge angle on edge retention; specifically, that edge angle greatly controls edge retention: read more

Reviews

Book Review – Damascus Steel Swords: Solving the Mystery of How to Make Them

Larrin

Thanks to Jason Volkert for becoming a Knife Steel Nerds Patreon supporter!

Introduction

In July 2018 a new book was released on the research of wootz Damascus steel by Dr. John Verhoeven. Dr. Verhoeven is well known for his contributions to research on knife steels and damascus, along with frequent collaborator Al Pendray. Dr. Verhoeven has often been cited on this website, including his articles on CATRA testing of different knife steels [1], and also a series of experiments on sharpening of knives [2]. He also wrote a book on the metallurgy of knife steels, which is now published as Steel Metallurgy for the Non-Metallurgist; I reviewed it in this article on book recommendations. Dr. Verhoeven had a particularly strong impact on my interest in steel and metallurgy. I was introduced to him through his knife steel metallurgy book which I read several times in my teen years. And when I was looking for the best steel University to attend, he was the first person I emailed for advice. I asked him for an interview to be published on this website, and he asked if I would be willing to review his new book instead – Damascus Steel Swords: Solving the Mystery of How to Make Them. read more

Corrosion Resistance, Edge Retention, Sharpness

Does Acidic Food Affect Edge Retention?

Larrin

Thanks to Bill Wine for becoming a Knife Steel Nerds Patreon supporter!

I was interviewed on the Knife Junkie Podcast, so make sure you check that out.

Acidic Food

Carbon steel knives are frequently used in kitchens, probably the majority of them made by Japanese bladesmiths and knife companies. Kitchen knives cut a variety of foods, and some of them are corrosive. There has been some debate about whether any of these potentially-corrosive foods can actually affect sharpness or edge retention of kitchen knives. Sharpness is controlled by the radius/width of the edge. You can read more in the article on sharpness vs cutting ability. read more

History - Articles - Books

Knife Steel Nerds 2018 in Review

Larrin

Here at the beginning of 2019 I decided to write up a retrospective of Knife Steel Nerds so far. A lot of things happened in 2018. First of all, the Knife Steel Nerds website was started, with the first article being posted February 27, 2018. That first article was about a modified 3V steel developed and patented by Crucible but never sold as far as I know. Links to the website were not shared with anyone until March 8th, however. read more

Interviews

Interview with Zvi of Zknives.com

Larrin

Thanks to the Knife Steel Nerds Patreon supporters for an awesome 2018!

Introduction

Zvi, who goes by Gator97 on many forums, developed the website Zknives.com which contains many articles on various topics including many on knives and sharpening. He also has a steel composition database which is the largest ever made collecting essentially any steel ever used in knives. As far as I know it is the largest database of steel compositions of any type. The database is available on his website and as Android and iOS apps. Because of that very useful contribution to knife steel nerds, I asked Zvi if he would be willing to be interviewed and he graciously agreed. read more

Steel and Knife Properties, Toughness

Why Cold Steel Is Brittle

Larrin

Thanks to Tracy Mickley from becoming a Knife Steel Nerds Patreon supporter!

Effect of Temperature on Strength

Steels become stronger at lower temperatures. This can be measured with the “yield strength” which is the load to permanently deform the steel. This deformation is in the form of a shape change, ie. if you are bending steel it stays bent, when hammering hot steel it dents, when flexing an edge it rolls. This is perhaps easier to visualize for those that have forged steel because hot steel is easier to forge, and is progressively more difficult to forge as it cools down. This increase in strength at lower temperatures continues below room temperature, so steel at cryogenic temperatures is stronger than at room temperature. Here are values for yield stress for 410 stainless steel heat treated to 39 Rc [1]: read more