Alloy steels need special homogenization annealing, but for carbon steel such treatment is not required. Alloy steels usually need longer time for austanisation (before quenching) than carbon steels. What are the reasons of this phenomenon? 

Now there's a simple question with tomes worth of answer. Have you skimmed through the knife making section? This very thing is covered in some depth by some very expert folk. I only know just enough of the basics to realize how ignorant I am and where to go to find out what I need.

Frosty The Lucky.

When you add sugar to lemonade you need to stir it for a while to get all the sugar dissolved. High alloy steels have, well, more sugar.

Some alloys maintain austenite structures, some alloys retard formation of other structures, some alloys dissolve into solid solution faster (some crystalline structures decompose into austenite faster than others as well), some structures of elements with carbon (carbides) require higher temps to dissolve and others require time at temp......its the wonderful variety of chemistry and physics..........

Ric

When you add sugar to lemonade you need to stir it for a while to get all the sugar dissolved. High alloy steels have, well, more sugar.

Ric

​That's beuatifully put, Richard! .

Well, William, a little bit more about the sugar and stuff here you can find something quite informational, too:

https://archive.org/details/EngineeringMetallurgy

It's not the newest but pretty cool reading.

Bests:

Gergely

From what I've figured out (with a great deal of help, and people willing to use very small words), is that with different unknown alloy steels, you should also try multiple tests for soak times at the curie temp before hardening, as it affects grain growth.

When a steel is forged, there is a possibility of atoms migrating to different areas. The soak time and temperature allows atoms to migrate such that there is a homogeneous mixture throughout the alloy. At a given temperature carbon migrates more rapidly than other atoms (ie, chromium, nickel, etc.) so the soak time and temperature is lower than more complex alloys. The simple steels form fine pearlite more readily than the more complex alloys. Cooling in the forge, ashes, or vermiculite is usually slow enough that course pearlite won't form. This aids in the workability of the cold steel. Alloys, need to be cooled differently to attain this goal.

Edited May 24, 201511 yr by Bo T

Metallurgy of Steel for Bladesmiths and Others Who Heat Treat and Forge Steel – by Professor Verhoeven

http://www.feine-klingen.de/PDFs/verhoeven.pdf

 

 

ASM Metals Handbook, (for my version   Heat Treating is Volume 2).  My got to place for information on how to handle a new alloy and how I learned that S1 does not profit from normalization before hardening...However as the charts and instructions are generally worked out for a 1" sq cross section I have to work out how to treat knife blade sections from there.

Try the "Workshop Practice Series" from Special Interest Model Books  

Number 1. Hardening, Tempering And Heat Treatment by Tubal Cain

ISBN 978--085242-837-5

in case any one is wondering, the OP has not returned to the site since posting his question almost 2 months ago.

Edited May 29, 201511 yr by Steve Sells

His loss

Thank you very much Guys 

Steve Sells,  just I've been reading the answer and try to understand it 

The logs stated you had not logged in since posting. Post once in a while get to know the membership, join in and be apart of things.  Also there was no need to use over size text,and bold in the entire thing.   other than that  Its fine,  I was just pointing out you had not returned, and we get too many the post and never return.

Steves "candy coated and PC butons" are broken, but his relitivly big heart is in the right place. 

Don't  lurk, sighn in lol, let us mnow your alive.

Quenchcrack, a metallurgist across the street, said once that annealing high carbon, straight carbon, steel was not as desirable as normalizing, because when you anneal you retain 'large carbides.' He said that large carbides were undesirable. From the time of that reading, I do not anneal W1 as a prelude to hardening. Sometimes, I will anneal it if I'm going to drill or file.

Alloy steels are a whole other ball game.

 

 

 

Actually most of the high carbon steels with some alloy content, such as 52100, will also form the large carbides Quenchcrack mentioned. These carbides are usually distrubuted along the grain boundaries and provide a ready path for crack propigation. Therefore, we do not use a conventional anneal with these grades. Rather, when a soft, machinable structure is required a spheroidize anneal is used. This multi step heating/cool cycle prevents the formation of the grain boundary carbide and instead promotes the formation of finely distrubuted carbide spheres. The easy crack path is avoided while still maitaining a workable structure. Also, since the carbon is now more uniformly distributed throughout the microstrucutre, the austentizing cycle prior to quench is more effective and can be shorter than when dealing with conventionally annealed versions of these materials.