Category: Heat Treating and Processing

3 thoughts on “Heat Treating and Processing”

  3. Ciao Larrin,trovo molto utile questo sito,
    Avrei una domanda riguardo all’acciaio A8mod:come é meglio temprarlo per raggiungere la massima durezza?

    Reply

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Cryo, Tempering, Toughness

Cryogenic Processing of Steel Part 2 – Toughness and Strength

Larrin

Thanks to Gator, Russell Dodd, and Matt de Clercq for becoming Knife Steel Nerds Patreon supporters!

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. read more

Cryo, Hardness, Heat Treating and Processing

Cryogenic Processing of Steel Part 1 – Maximizing Hardness

Larrin

Thanks to Hiroaki Misono and Robert Venable for becoming Knife Steel Nerds Patreon supporters!

Heat Treating and Austenitizing

During heat treatment of steel, the steel is heated to a high temperature called the “austenitizing” temperature where a phase called austenite is formed. Steel has different phases which refer to different arrangements of iron atoms within the steel. Austenite has a different set of properties from the typical room temperature phase of steel. One example of the different properties of austenite is that it is non-magnetic unlike the room temperature ferrite or martensite. read more

History - Articles - Books, Powder Metallurgy, Steel and Knife Properties

All About D2 Steel – Development, Use in Knives, and Properties

Larrin

Thanks to Robert Erickson, knifeandgear_swiss, Dale Bushness, and Paul Hart for becoming Knife Steel Nerds Patreon supporters!

Update 10/22/2020: I now have an article with how to heat treat D2, PSF27, and CPM-D2 and it also includes toughness testing of each steel and edge retention testing of D2. https://knifesteelnerds.com/2020/08/31/how-to-heat-treat-d2-psf27-and-cpm-d2/ read more

Silicon-Alloyed, Tempering

Silicon Additions for Improving Steel Toughness

Larrin

Thanks to Colin Shannon and Robert Williams for becoming Knife Steel Nerds Patreon supporters!

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]: read more

Austempering, Heat Treating and Processing

Bainite vs Martensite – The Secret to Ultimate Toughness?

Larrin

Thanks to Thomas Busch for becoming a Knife Steel Nerds Patreon supporter!

Misc. update: I have added a set of supporting micrographs to the introduction to Austenitizing steel. 

Tempered Martensite

To begin describing what bainite is it makes sense to start with martensite first. To form martensite we heat up the steel to high temperature to transform to a phase called austenite where we dissolve carbon in between the iron atoms (see Austenitizing Part 1), then quench the steel to lock in the carbon and form a hard phase called martensite (see What Makes Quenched Steel so Hard?). Following that we temper the martensite to allow some of the carbon out and increase the ductility of the martensite; the carbon comes out as very small carbides, a compound of iron and carbon (see What Happens During Tempering?). In the article on martensite formation I shared the following YouTube video to see the formation of the martensite laths: read more

Heat Treating and Processing, History - Articles - Books, Metallurgy Principles, Reviews

Review – Kevin Cashen’s Guide to 1080 & 1084

Larrin

Thanks to Edward Braun, Mark Reich, and Alex Kaplan for becoming Knife Steel Nerds Patreon supporters!

Misc. updates: I added some toughness numbers that I had previously been unable to track down comparing 440C and 154CM to the 154CM article. I also added a summary of a very interesting new journal article about the effect of grain size on steel toughness to the Grain Refinement article.   read more

Heat Treating and Processing, Steels, Tempering, Toughness

Toughness testing – Cru-Wear, Z-Wear, Upper vs Lower temper, Cryo vs No Cryo

Larrin

Thanks to Paul Hart and James Covington for becoming Knife Steel Nerds Patreon supporters!

I recently completed some toughness tests on samples that were heat treated by knifemaker Warren Krywko. The steel was donated by Chuck Bybee of Alpha Knife Supply. The samples are subsize unnotched charpy specimens with dimensions as specified on the bottom of this page: http://knifesteelnerds.com/how-you-can-help/ If we can get more people to make toughness specimens we can have more comparisons between steels, hardness points, heat treatment parameters, etc. Patreon dollars are for the purpose of paying for machining, shipping, testing, etc. for tests like toughness and CATRA edge retention, so if you are able to contribute that way please visit the Knife Steel Nerds Patreon page.  read more

Metallurgy Principles, Quenching

What Makes Quenched Steel so Hard?

Larrin

Update: I have started a Patreon page to fund research projects which you can read about here – http://knifesteelnerds.com/how-you-can-help/

To harden steel you heat it up to high temperature to form a phase called austenite, followed by rapid quenching to make a very strong phase called martensite. Hardness is a measure of strength. I covered the process of austenite formation in the following post: Austenitizing Part 1. To summarize that post: read more