If creep behavior can begin at 0.6T(melting) but, hot working for a pure metal starts at 0.4Tm, what is the explanation for this?
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1$\begingroup$ Are you implying there is some issue with the creep temperature being hotter than the hot working temperature? Is so, I think you need to clarify why you think that is an issue. After all, you can cold work a metal at 0Tm. Is that an issue because the temperature is lower than the creep temperature? $\endgroup$– JohnHoltzCommented Oct 7, 2019 at 2:02
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$\begingroup$ Your assumptions are wrong for the real world. Carbon steel ( MP 2700 F) creeps at 800 F and probably at 700 F ( if you wait long enough.). $\endgroup$– blacksmith37Commented Oct 7, 2019 at 13:52
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Hot work involves macroscopic deformation of the metal; no time is allowed for creep to take place so the concept of "creep" as such doesn't exist during hot work.
The objective of hot work is to deform the workpiece to its desired shape at a temperature at which it happens to be easily malleable and will not strain-harden in the process. This means that the temperature you choose depends on exactly how soft you want it to get and how hot you need to get it so that solid-state diffusion through the lattice is more or less fully activated.
answered Oct 7, 2019 at 16:22