Stiffness of steel after hardening

Can anyone tell me if the elastic modulus (Young's modulus) of steel
significantly changes after through hardening a steel component?
As elastic modulus is stress / strain up to then yield point, my view
is that the elastic region on a stress vs strain graph just gets longer
without the gradient changing.
Therefore hardening only increases then strength of the steel allowing
more stress and elongation to occur prior to yield.
Is this correct?
Regards
Martin
Reply to
colenum
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Yes. Hardening doesn't change the elastic modulus of steel appreciably, nor does carbon content. Just about any ordinary carbon or alloy steel will have a Young's modulus of about 30 million psi, regardless of treatment. Stainless and structural steels are a little less (28 or 29). Cast iron is quite a bit less rigid (maybe half).
Don Kansas City
Reply to
eromlignod
The elastic modulus does not change. Nor does the density or poisson's ratio. The yield stress will change though. It will increase if the material is hardened.
this is a matweb link for annealed AISI 1080 steel (yield 55 ksi)
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this is a link for AISI 1080 heat treated (yield 122 ksi)
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You'll see the other material props are the same.
Reply to
jmullner
It is interesting to note that this is a common misconception in engineering. Increasing the strength or hardnesss of steel does not make it stiffer. It takes the same force to bend it the same amount; it can just bend farther without yielding or breaking. That's why using a higher strength steel in a spring does not increase its spring rate.
Don Kansas City
Reply to
eromlignod

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