Hie stress-strain curves of 0.006 7C-0.045 0Ti Ti-IF (interstitial free) steel with deformation temperature 750 - 900 °C and deformation rate 0.1 - 40

-1

has been tested and obtained  Ihennecmaster-Z thermal simulation test machine

based on that the relational expression between Zener-Holloman parameter Z and deformation rate ε - temperature T (K) ： Z= e exp (39 507/T) is defined

and the critical strain fonnula for relation between critical strain ec and original grain size Z parameter： e

c

= 2.314 4 x 10

-3

X d

-0.8003 9

×Z

0.050

is established. The results showed that with same deformation rate the dynamic recrystallization of steel occurred most easily at 850 ℃

as deformation temperat

ure increased to 900 °C (dual phase region)

the dynamic recrystallization un-occurred even at low deformation rate (1 s

-1

)

and as deformation rate was more than 10 s

-1

the dynamic recrystallization of Ti-IF steel also un-occurred during hot rolling. With comparison between predicted value of critical strain and measured value

the average error was no more than 5 % .