Carbides, Steel and Knife Properties

Carbide Types in Knife Steels

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Cementite

The most basic carbide type in steel is an intermetallic compound formed between iron and carbon, commonly called cementite. Carbides are hard and brittle, similar to a ceramic material. Cementite has a relatively complex structure but in its simplest form it is 3 iron atoms for every carbon atom: Fe3C. However, other elements can partially replace the iron, so the carbide is sometimes given as M3C where M can mean Fe, Mn, Cr, etc. Cementite is typically present as either particles or in “pearlite.” I introduced what pearlite is in this article. However, cementite is the only carbide type that typically forms in pearlite, so to keep things simple for this article I will be focusing on carbide particles. Below I have a schematic representation of carbides (black circles) along with the grain boundaries (black lines). read more

Austempering, Austenitizing, History - Articles - Books

The Secret Heat Treatment of Frank J. Richtig

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Legendary Heat Treatments

Last week I wrote about What a Good Heat Treatment Can and Cannot Do, and as part of that topic I wrote about how some knifemakers have a legendary or even mythical reputation for their heat treatments. In that article I argued that the big differences are between “bad” and “good” heat treatments, and that the differences between various good heat treatments are much smaller. And that edge geometry and knife design are more important to knife performance than the differences that are possible between different “good” heat treatments. So I think it makes sense to discuss a particular case of a knifemaker known for legendary, unmatched heat treatments, which brings me to… read more

Heat Treating and Processing

What a Good Heat Treatment Can and Cannot Do

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The Legend of Heat Treatment

There is some debate about knives that have steel with a “good heat treatment” vs those that have a bad or sub-par heat treatment. Some knifemakers have a near legendary reputation for their excellent heat treatments. What exactly is possible in terms of heat treating? How much better can steel be? How bad can it get? read more

Austenitic Stainless, Corrosion Resistance, History - Articles - Books, Steel and Knife Properties

H1 Steel – How it Works

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Austenitic Stainless Steels

At its most basic, H1 is an austenitic stainless steel. Austenitic stainless steels are about as old as stainless steel itself, being developed by German metallurgists in the approximate time period of 1909-1912. They worked on 18% Cr, 8% Ni steels which are quite similar to common austenitic stainless steels like 301, 302, and 304. read more

Annealing

How Annealing of Steel Works – Subcritical vs Transformation Annealing

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Why Anneal?

There are three primary goals of annealing steel:

  1. Make the steel machinable so that it can be easily cut, drilled, and ground.
  2. Setup the steel for austenitizing and quenching (hardening) so that is has good heat treating response
  3. Provide the best possible properties in the final heat treated product

The above goals are not always 100% compatible, but we would like to offer the optimal combination based on our priorities. However, to know what the trade-offs are we need to know how annealing works first. read more

Austenitizing, Heat Treating and Processing, Toughness

How to Heat Treat 52100

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52100 Steel

I previously wrote about the history and properties of 52100 in this article. The steel has been around since 1905, has been known as 52100 since 1919, and has been used in knives since at least the 1940’s. It was developed for bearings and its common use in bearings meant it has been a ready source for knife steel for decades. It is known for its fine carbide size and good toughness. The chromium addition compared with the chromium-free 1095 means that it has somewhat higher hardenability so it is easier to harden in oil and obtain full hardness. The chromium also helps keep the carbide size small. The chromium also shifts up the temperatures required for hardening. read more