Steel and Knife Properties, Stress Risers

How Stress Risers Lead to Broken Blades

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Stress Risers/Concentrations

In an ideal world when a force is applied to a knife, that stress is distributed evenly across the piece. There can be certain features to a design, however, that leads to a stress “concentration” where the stress is locally higher than the rest of the piece. Stress is load divided by cross section, so a very simple way stress is concentrated is by having a locally smaller area of a part. read more

Heat Treating and Processing, Toughness

How to Heat Treat 5160 – Optimizing Toughness

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5160 is a low alloy steel known for its excellent toughness. It has been used by many forging bladesmiths due to its good properties and also wide availability, especially in the form of leaf springs. However, information on how to maximize the steel’s properties with heat treating is scant. So along with my father, Devin Thomas, we did a small study on the toughness of 5160. read more

Austenitizing, Cryo, Hardness, Heat Treating and Processing, Nitrogen-alloyed, Tempering

Heat Treating Vanax – How Hard Does it Get?

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Vanax is an interesting steel because of its good combination of toughness, wear resistance, and corrosion resistance. I wrote about Vanax along with other nitrogen-alloyed steels in this article, to describe how the steel is designed. While the datasheet shows it being capable of 59-61 Rc, I was curious about how hard the steel can go. The steel may be good for kitchen knives, for example, where very thin edges and high hardness is common. And kitchen knife users may appreciate the excellent corrosion resistance of Vanax in the presence of water, salt, and acidic foods. read more

Austenitizing, Magnetism

Can You Trust Your Magnet During Heat Treating?

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How a Magnet Helps in Heat Treating

It is somewhat common for knifemakers to heat treat low alloy steels in a forge or with a torch, two methods where tight temperature control is not possible, and the temperature is frequently not even known. A magnet is often used to check the temperature of the steel because the point at which the steel becomes nonmagnetic is near the temperature at which the steel should be quenched to achieve high hardness. How does steel magnetism work? How reliable is checking the steel with a magnet? read more

Cold Forging, Heat Treating and Processing

Cold Forging of Steel

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Cold Forging

Cold forging is a lot like hot forging except it is at or near room temperature. The lower temperature means that the steel is much stronger and it is much more difficult to forge. That also means the steel is more brittle and therefore more likely to crack during forging or rolling. The shape of the grains in the steel are changed through forging. You can read about what grains are in this article. Steel is made up of planes of iron atoms, and if the steel was made up of only one grain these planes of atoms would all be parallel to each other: read more

History - Articles - Books, Steel and Knife Properties, Steels

All About AEB-L

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History of AEB-L and 13C26

Tracking down the history of AEB-L was surprisingly difficult. The Uddeholm website claims that AEB-L was patented in 1928 [1]; however, that is not entirely truthful. Uddeholm did patent a stainless steel in 1928 [2], which was named AEB, and later AEB-H to differentiate it from AEB-L. This was a very early stainless steel, so its development and patent needs to be viewed in that historical context. You can read about the development of stainless steels in this article. The AEB patent was for 0.7-1.1% carbon, 10-16% chromium, and 0.75-2.0% manganese. The original Brearley and Haynes stainless steel patents were still in effect; they got around them by using a higher carbon content than the Brearley patent (had a 0.7% max), and by claiming that high Mn led to improved corrosion resistance (it actually doesn’t). The nominal composition of AEB became 1% carbon and 13.5% chromium, which gave it a relatively large carbide structure compared to AEB-L, but it did see some use as a razor blade steel. read more

Hardenability, Quenching

How Fast Do You Have to Quench? Hardenability of Steel

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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?

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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