Annealing

How Annealing of Steel Works – Subcritical vs Transformation Annealing

admin

Thanks to Larry Corsa and Gene Kimmi for becoming Knife Steel Nerds Patreon supporters!

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

Larrin

Thanks to Lev Serebryakov for becoming a Knife Steel Nerds Patreon supporter!

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

Forging

Which Steels are Easiest (and Most Difficult) to Forge?

Larrin

Thanks to Richard Airey for becoming a Knife Steel Nerds Patreon supporter!

Forging Steel

Typically forging bladesmiths have restricted their steel selection to low alloy steels like 1095, 1084, 5160, 52100, O1, etc. There are a variety of reasons given for why the bladesmiths usually use these relatively simple steels. Often “ease in heat treatment” is a common one. However, this article will focus on which steels are physically more difficult to deform with the hammer and which crack most readily. What controls “forgeability” or steel? read more

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

A2 Steel – History and Properties

Larrin

Thanks to Dan Pierson, Steve R. Godfrey, Bryan Fry, and Timothy Becker for becoming Knife Steel Nerds Patreon supporters!

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

Larrin

Thanks to Peter Bruno for becoming a Knife Steel Nerds Patreon supporter!

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