Category: Tempering
Introduction to Knife Steel Heat Treating from a Metallurgist
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Intro
I have many articles about all of the nitty gritty details of heat treating and the metallurgy behind every step. However, there may be some cases where knifemakers are afraid of all of the terminology and science and think heat treating is too complicated for them. When it comes down to it, the steps of heat treating are not particularly difficult. When you follow a recipe for how to make cookies you don’t need to know the science behind every step, but following them will still get you cookies at the end. An expert would know what went wrong if your cookies were too crunchy, too puffy, spread out too much, etc. And how to modify the recipe to change the flavor and texture of the cookies. However for most of us we will just follow the recipe. You can do the same thing with heat treating knife steel! So for this article I will tell you how to follow a datasheet. I will include some links to articles with more information about what happens in each step, but you can get to those when you are ready. Another great place to learn more about heat treating is my book Knife Engineering: Steel, Heat Treating, and Geometry.
What is the Best Hardness for MagnaCut Knives?
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Chris Hancock, Chad Morris, Edward Voss, Liam Gogley, Erik Turner, Nathan Raptis, Nick Dunham, Joe Busic, Will Red Five Forge, Dmitry Kiyatkin, Edward Edmonds, Asinelli, Mattew Reagan, Nate, Dan Barrett, Malachi Chou-Green, Nats Spawnee, McKenzie Kelsay, Jantz Supply, Adam Webb, Brian Baley, Blade HQ, and Mark Demshock.
How to Heat Treat 8670
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Podcasts
I appeared on two podcasts this past week, Knife Perspective and Mark of the Maker. Knife Perspective I had been on before so we mostly focused on MagnaCut and other topics. Mark of the Maker was a full interview asking about my background before discussing my book, website, and CPM MagnaCut. So listen to one or the other or both depending on what you’re in the mood for.
How Even is an EvenHeat? How to Operate Furnaces Effectively
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How to Use a Steel Datasheet to Develop a Heat Treatment
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Testing the Edge Retention of 48 Knife Steels
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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.
Heat Treating Vanax – How Hard Does it Get?
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Vanax
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.
Cryogenic Processing of Steel Part 2 – Toughness and Strength
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Introduction
Part 1 of the Cryogenic Processing series covered the transformation of retained austenite to martensite and the increase in hardness that occurs. That is the least controversial aspect of cryogenic processing of steel. The other two primary properties of steel affected by cryo processing are toughness and wear resistance. Both of these properties can be difficult to pin down as they have high variability. Tool steels are known for their relatively poor toughness which means we are often comparing small numbers.
Silicon Additions for Improving Steel Toughness
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High Toughness Steels
There are a series of shock resisting steel designed for high toughness (see this article to learn about toughness). A popular one is S7, an air hardening steel that can reach relatively high hardness. Another steel in the “S” series, S5, is reported to be even tougher [1][2][3][4]: