The precipitating behavior of secondary phases bearing Nb

Ti and Cu in high performance bridge steel (% ： 0.07C

1.52Mn

0. 17Si

0.003S

0.013P

0. 30Cr

0.40Ni

0. 68Cu

0. 19Mo

0.01V

0.01Ti

0.04NE) in two stage control rolling and cooling process (1 006 ~979℃ and 813 ~782 °C ) from 250 mm casting slab to 30 mm plate and in tempering at 600 °C has been studied. Results show that there are precipitates of secondary phases during all control rolling and cooling process and later tempering process: in higher temperature roiling zone the ≥50 nm cubic TiC particles are first precipitating

in flowing deformation process the 10-25 nm NbC particles precipitate； during tempering process the NbC particles nucleate attached to TiC particles and grow up

besides

the 3 ~ 30 nm Cu dispersed precipitates are observed.