Re: [CAD_CAM_EDM_DRO] Re: cast iron

Hi all,
Considering the variety of responses to stress
relieving in cast iron prompted me to grab the
book and try to understand what goes on.

Quoting from the ASM book on steel: cast iron
chapter pg 437

"Subcritical heating is used for both stress
relief and annealing. Temperatures between 550 C
and 650 C (1022 and 1202) F are used to relive
stresses without significantly lowering strength
and harddness, while higher temperatures, between
700 and 760 C (1292 and 1400 F ) are used to lower
hardness for improved machinabiliity by
shperoidiizing matrix pearlite. Much higher
annealing temeratures in the
austenite-carbide-graphite phase field, 900 to 955
C (1652 to 1751 F) are used to transform very
hard, massive carbides to graphite.
Microstructures with extensive massive carbides,
i.e. white cast iron microstructures, may form in
thin sections of gray cast iron. These
microstructures are almost impossible to machine,
and where possible should be avoided by casting
and alloy design rather than heat treatment.

Now even I almost understand this: ;-)

You pick what you want and make it so.

HTH

Dave