Effect of cooling rate after rolling (20 ~0. 5 °C /s)

initial pass temperature of finishing rolling ( 1 000 ~ 900 °C )

last pass temperature of finishing rolling (860 ~750 °C ) and coiling temperature (630 ~ 500 °C  ) on niicrostnie- ture of pipeline steel X65 (0. 08% C

1. 38% Mn

0. 032% Nb

0. 041 % V

50 x 10

-6

N ) has been studied by using Gleeble-3500 thermal-mechanical simulator. Results showed that with increasing cooling rate after rolling

decreasing reduction ratio at about 950  °C 

decreasing finishing and coiling temperature

the microstructure of plate products was finer. The rolling temperature for 7. 1 mm finished plate rolled by 150 mm x 1 700 mm slab was proposed that 1 150 ~ 1 200 °C heating

rough rolling ≤1 130 °C to 35 mm

initial pass finishing rolling 950 ~ 1 020 °C

last pass finishing rolling ≤83O °C

and coiling

≤580 °C

and the mechanical properties of products met the requirement of standard.