The structure of TRIP(transfornation induced plasticity)steel 0.20C- 1.08Si- 1.43Mn during continuous cooling has been studied by Gleeble- 1500 thermal simulation machine to get CCT( continuous cooling transforation)curves  and to obtain that the bainite particle occured with cooling rate 10 ℃/s and the lath bainite got with cooling rate 15 ℃/s.  The thin slab casting and rolling process test of 0.20C- 1.54Si- 1.55Mn TRIP steel melted by a 10 kg vacuum induction furnace with ingot dimension 60 mm×100 mm×130 mm was carried out in laboratory which was rolled to 6.40 mm plat by 7  pass rolling with finish rolling at temperature 810 ℃

and air cooling to 700 ℃ than water cooling to 400 ℃ to simulate  coiling. The test results showed that there was 5. 13% retained austenit

e

37.20% bainite and the rest-ferrite in structure of  steel

of which the mechanical property- σ

b

was 715 MPa

σ

s

520 MPa

ratio of yield strength to tensile strength 0.73 and  elongation δ 20%.