Couple of questions

G

grizzled gizzard

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Aug 31, 2010
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What tends to refine the grain of steel - 52100, as opposed to what causes grain to grow? Is there a simple answer? Is this a "law" of all or most steel?

My other question kind of ties into this. Is there a chance to change the grain size or structure during annealing? I'm not even sure what full annealing takes, or if it's necessary.

I've been getting good results with what I'm doing, but I want to understand it more, and see if I could do better.

Thank you for your time, gentlemen.
 
Grain is reduced by taking it back to austinite, allowing the grains to go back into solutuion, and then reforming them. This is done multiple times at lowering temperatures. The last cycle is done below the critical point. This will yield the finest grain structure as well as fully annealed steel. It is often referred to as "cycling down the steel".

A brief description would be ( in Fahrenheit):
Heat to 1500 and soak for 10 minutes
quench in oil
heat to 1400 and soak
quench in oil
heat to 1350 and soak
quench in oil
heat to 1250 and soak briefly
air cool to 800-900 ( black heat) and quench in oil
 
Thank you very much, Stacey. You are forever truly helpful.

So refining the grain is actually very much related to annealing?

And growing grain is related to hardening it, I take it?

Is that about all there is to it?

Thanks a bunch once again. I really really do appreciate being able to ask questions here. Thank you for your time in answering, Stacey.
 
It that all there is to it - Not quite.
Refining the grain is a thermal process and annealing is a thermal process. They are different things. Grain refinement is done by hardening the steel multiple times, lowering the temperature to just above critical in three steps. This is followed by an annealing because the steel would be fine grain but hard if you just quit there. The last step, the sub-critical annealing, will leave the metal soft and workable.

I would suggest you read Kevin Cashen's posts on working with three steels ( in the stickies), as well as his metallurgy articles on his website. There is a lot of other good metallurgical info in the stickies,too.

Growing the grain is due to the steel being held at temperatures well above the target point ( above 1550F for 52100). At those temperatures and given enough time, the grains merge, thus making bigger and bigger grains.
 
Thank you so much for the concise answers. That is exactly what I was hoping for, then I can research from here.

That was perfect. Thanks a bunch!
 
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