Double normalizing in steel heat treatment

[stanislasdz]

I found this in a old book intitiled "Steel Casting" and i have somme questions :

1- Why double normalizing refine the grain size ?
2- What about double normalzing Vs quenched and tempered steel ?
3- Why tempering after double normalizing ?
4- What about double tempering ?
5- What about double quenching ?

Many thanks

 

[metengr]

stanislasdz;
There is no easy answer your questions above. I would suggest the following;

Perform a Google search, similar to the one below

http://www.google.com/search?hl=en&...alizing+heat+treatment+practices&start=0&sa=N

The double normalization heat treatment practice would be more applicable to low alloy steels versus carbon steels. I have seen the initial normalization performed as a conditioning treatment prior to final heat treatment. Conditioning in the sense to reduce distortion. Some of the high strength low alloy steels contain microalloy additions that benefit by a conditioning heat treatment followed by normalizing or quench and tempering to obtain desired combination of mechanical properties (strength, toughness and ductility). Double tempering would benefit alloy steels that exhibit high hardenability and have the potential for retained austenite after the initial normalizing or quench and temper heat treatment.

 

[Robertmet]

Custom knife and sword makers are often double or triple normalizing create finer grain size .That's done with even 1 % carbon steels though more often with .60-.80 C. Stainless steel and other high alloy types usually have enough elements to to have fine grain to start.