Category: Steel and Knife Properties

2 thoughts on “Steel and Knife Properties”

  1. Those photos and drawings will help people understand ! Orientation – I was curious about what Crucible does with that .Their CPM goes to Niagra Metals for rolling and they cross roll the steel. Cut into squares and rolled alternating direction to minimize directional properties. I think Matt Gregory found that in his visit.

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Austenitizing, Magnetism

Can You Trust Your Magnet During Heat Treating?

Larrin

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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

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

All About AEB-L

Larrin

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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

Larrin

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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

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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

Corrosion Resistance, Edge Retention, Sharpness

Does Acidic Food Affect Edge Retention?

Larrin

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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

Steel and Knife Properties, Toughness

Why Cold Steel Is Brittle

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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

Cryo, Edge Retention

Cryogenic Processing of Steel Part 3 – Wear Resistance and Edge Retention

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Intro to Cryo and Wear Resistance

In Cryogenic Processing Part 1 I covered the effects of cryo on retained austenite and hardness. In Cryogenic Processing Part 2 I looked at the studies on cryo and toughness. Wear resistance is the most controversial aspect of cryogenic processing of steel. In particular there are claims that the use of cryogenic processing (liquid nitrogen) leads to an improvement in wear resistance that is not found with subzero processing (dry ice). Sometimes it is claimed that cryo can lead to massive increases in wear resistance [1]: read more