# Soften Case Hardened Cast Iron



## MikeMc (Jun 22, 2015)

Can any one tell me how hot I need to get a piece of case hardened cast iron to soften it.
At the moment it's hard enough to have dulled 2 center punches, one a Starett and the other a piece of chromolly I made and hardened 30 years ago.
Thanks,
MikeMc


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## T Bredehoft (Jun 22, 2015)

Heat it glowing red and cover it deeply with hot ashes which should keep it hot allowing it to cool very slowly.


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## RJSakowski (Jun 22, 2015)

Cast iron is not normally case hardened.  It has a fairly large percentage of carbon and the case hardening process would make it brittle.  White cast can be quite hard.  You might try annealing the piece by heating it to a temperature of 1475 to 1650F and soaking at that temperature long enough for the interior to heat as well.  Then cool slowly back to room temperature.


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## brino (Jun 23, 2015)

Mike,

Does the piece need to hardened again after you are done machining?

-brino


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## Flammable_Solid (Jun 23, 2015)

To not heat treat the whole piece, grind through the case hardening to then complete your machining.

Cast irons (both grey and ductile) are usually induction hardened at the surface but it shouldn't be more than 0.030" deep.


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## MikeMc (Jun 23, 2015)

Thanks fellows and no it doesn't need to be rehardened.
MikeMc


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