The Specifics of the Microscopic.

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omegaTWINKIE

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May 10, 2015
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Hello there. This is my first time asking a question on this forum, and I'm hoping that you guys would be able to answer this question. I'm also hoping that this isn't a stupid question.

So, here it is: what exactly happens in the atomic lattice (the atoms and atomic structure of all of the elements, i.e., carbon atoms, chromium atoms, etc.) of steel during each of the phases of forging and heat treating (quenching, tempering, hardening, annealing, etc.)? How does the amount of heat and time determine the manipulation of a steel's atomic lattice, and how does that manipulation alter the properties (hardness, strength, toughness, etc.) of the steel? Answers as specific as possible would be greatly appreciated.

Sorry if that really is a stupid question, or if it's already been well-answered. If it's the case of the latter, could I trouble someone to please post the information, whether it be a website or forum post?

Any helpful answers would be very much appreciated.

Thank you guys in advance.
 
Wow, talk about a HUGE question. Books ( lots of them) have been written on this subject. The advent of the SEM has made many changes in previous theory. The stickys at the top of the Shop Talk page has some good metallurgy info, some of which delves into the changes you ask about.

Chaps like Kevin Cashen ( and several others here and on hypefreeblades.com) have spent their lives taking micrographs and studying these changes. Googling his work may give you some insight ( most of the time it just makes peoples head hurt). A post on hypefreeblades may get a more detailed answer.




The simplest answer is that there are certain arrangements of the atoms that form crystals and structures, The main ones we deal with in knife HT are body centric carbon and face centric carbon. These two change state as the steel crosses the critical point at Ac and Ar.

The next set of structures we deal with are the way the carbon/iron structures form. In knives, these are mainly austenite, martensite, and pearlite. These structures also have different arrangements like lathe and plate formation.

In tempering, the structures formed in hardening have very high stress in the arrangement. The tempering allows these structures to "slip" a bit and ease the tension. This looses a little hardness, but gains toughness.

Most any book on metallurgy has the what and when info on these changes. Understanding it can be quite confusing.

If you read German, the book by Roman Landes is specifically written about making knives and cutting tools ( specifically razors). It is called "Messerklingen und Stahl" . Fo r ten years the publishers have talked about publishing it in English...I hope they do someday.
 
Much of that includes the subject of crystallography. Cubic, tetragonal, hexagonal are the basic struictures. Changes in those structures include formation or transformation austenite to martensite == shear type ,fast.They are speed of sound fast.Take a 1/4" rod of zinc , bend and listen -the formation , fast like martensite, of 'twins' .
 
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