flow stress models

Hie,
1] I am Krunal, currently pursuing my masters for University of Sheffield, wherein for my thesis I require to simulate the forging process for commercial vehicle Anti-roll bars using MSC MARC software. 2] I require the flow stress curves for the material 51CrMoV4 at varying temperatures ( approx 850 - 1400 deg celcius ) and varying strain rates ( approx 0.01 to 50 per second). However I am unable to find it....!!

A couple of years ago a colleague who wanted to simulate high-speed machining asked me: " Which is the best phenomenological flow stress model for metals?" I wasn't able to give an answer right away and decided to look in the literature.

What I found was, every ten years or so, a new model appears in the literature that tries to solve some of the problems of older models. However, a clear ranking of models has not been established yet.