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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Corrosion Resistance, Edge Retention, Edge Stability, Steel and Knife Properties, Toughness

How to Design Knives that Do Not Fail

Larrin

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Failure Modes

A common engineering technique is to evaluate designs based on how they failed, or may fail. Failure modes are identified and the designs are modified to prevent those failures. These ideas are simple in concept but it is surprising how easy it can be to miss the forest for the trees. In terms of predicting failure modes in some cases it is easy and in some it is difficult. You would expect a large chopping knife to require heavier edge geometry to prevent chipping and rolling, or a seawater diving knife to require high rust resistance. Other times failure modes are identified through testing of the knife or by returns from customers. Whatever the source of the failure, there are usually relatively simple methods for fixing each one, though the trade-offs for doing so may not be desirable. read more

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

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

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

Austenitizing, Edge Retention, History - Articles - Books, Steels, Tempering, Toughness

A2 Steel – History and Properties

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History

A2 steel is quite old, though determining the exact year it was released is a bit difficult. A2 steel was developed in the early 20th century during the explosion of tool steels that occurred after the discovery of high speed steel which was first presented in 1900. You can read about that history in this article: The History of the First Tool Steel. During the development of the first high speed steel included the switch from manganese to chromium as the primary hardenability element, and most high speed steels had about 4% Cr. That high chromium content was primarily for “hardenability” which is the degree of cooling required to achieve full hardness. A “water quenching” steel has low hardenability and must be quenched very rapidly from high temperature, and an “air hardening” steel can be left in air and it will fully harden. You can read more about hardenability in this article on quenching. The first high speed steel came to be known as T1, which had 4% Cr and 18% W (tungsten). The earliest record I have found of a precursor A2-type steel is in a summary of tool steels in 1925 [1], while summaries of tool steels from 1910 [2] and 1915 [3] do not have any similar steels. Therefore these types of steels probably arose sometime between 1915 and 1925. read more

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