Based on the hot simulation test  the effect of deformation condition and microalloying element 0.0180.056NB

0.01 - 0.02V and 0.01 - 0.02Ti on behavior of hot deformation of 0.06 - 0.08C test steel has been analyzed. And based on the Sellas-Tartat equation

the mathematic models to calculate the stress- strain curves have been established

that are dynamic recover model

σ

(e)

+ (σ

p+

σ

o)

[1-exp(-3.23ε/ε

s

)]

0.5

where

σ

p

- peak stress

σ

o

- stres

s at onset of plasticstrain

ε- strain

ε

s-

strain to onset of steady state by work hardening and recovering

and dynamic recrystallization model -

σ

=

σ=σ

(e)

-(σ

p

-σ

ss

)｛ 1- exp[-2.363(ε-ε

c

)ε

c

0.3425

)

2

｝

where

σ

ss-

stress to onset of steady state by dynamic recrystallization

ε

c-

strain for onset of dynamic recrystallization. The predicted results to rolling force by the models conform with that of measured value of 0.07C-0.018Nb test steel during commercial rolling.