Here we are using AISI 1010 grade wire rod and rolling to various sections but we are achieving the Yield strength out of customer spect. How to reduce yield strength and what are the parameter work s behind such higher Yield strength???
Keyur:
By wire drawing and rolling your AISI 1010, you are simply strain hardening your mild steel (dramatically increasing the dislocation density and causing tangling of dislocations which severely restricts their mobility), which can significantly elevate the yield strength and at the same time markedly reduce the tensile ductility. To return the steel to its pre-deformed virgin state, you simply need to anneal it at a temperature in excess of a third of the melting temperature to permit diffusion to occur. This will lead to the occurrence of "recovery" (reduction in the point defect and dislocation population) and more importantly "recrystallization" (the formation of a new grain structure); if you continue to anneal, eventually grain growth (grain coarsening to reduce the grain boundary surface area) will occur which will further lower your strength level.
Specifically, you could heat the material at a temperatures up to about 760C and hold it there, but with a low carbon steel this could take a long time. Alternatively, you could take it above the austenitizing temperature (~900C) and then slowly cool or air cool (normalizing) back to the ferritic state - this is a more rapid means to remove the effects of strain hardening. However, the precise heat treatment will depend upon the degree of cold work in the steel after working, the size of the parts that you are cold working, and most importantly what your required specification of the yield stress is. I would recommend that you do some experiments first with pieces of metal that you have cold worked using hardness measurements to estimate the strength level after each trial heat treatment.
ROR
I agree with Robert O Ritchie. It is necessary to eliminate the effect of cold forming using a recrystallization annealing.
Thank you for your answer.
Please help me on this.
1- Already we have rolled section by hot rolling around 10 Mt material, now customer complaining due to getting higher yield strength on section.
Presently we have 10 Mt on stock with higher yield strength around 430 N/mm2.
Now let me know how to reduce yield from 430 to below 285?
Is any heat treatment present? How it works? Is any damages occurs on section shapes? If any heat treatment possible the let me know the cycle of heat treatment......
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