[TheForge] Welding 5160

[Thomas A. Troszak]

 > From: "gblacksmith" <gblacksmith@alamedanet.net>
> Subject: Re: Re: [TheForge] Welding 5160
> Date: Mon, 25 Aug 2003 17:40:37 -0700
 
> Thomas:  Ditto....the "something happening" you refer to is the formation of
> austenite over time, at the critical temperature.  This critical temperature
> must be held long enough for this transformation to occur.  Your
> observations support what is known to  be physical law.  Upon reaching the
> austenitic state, elements such as iron, tungsten vanadium and molybdenum
> join carbon in solution.


Dear Grant,

I have a real question this time. I once poured a casting from zinc, and
when cut and etched, it was apparent that the grains near the "chilled"
outer edges were quite small, and the grains near the center were quite
large, where they had time to grow before (or during) solidification.

Is there a corresponding effect occurring in the tool steel? Will tool steel
"as quenched" have smaller grains (and thus greater hardness and
brittleness), and then do they (the grains) grow again while tempering (thus
helping making the steel tougher)?

Am I even close?  Or is grain size not a factor?

Also, It seems to me that the fracturing of larger, tougher grains into
smaller grains (by mechanical stress) is essentially the mechanism of "work
hardening"  Yes, No?  Is a light about to go on in my head, or am I barking
up the wrong track here?

I am actually really curious to know, even if I have put my foot in my
keyboard again...

Tom Troszak