The mathematical model for heat transfer of pipe line steel X80 (/% : 0. 04C

1. 85Mn

0. 25Si

0. 006P

0. 003S

0. 30Ni

0. 21Mo

0. 06Nb

0. 02V) 238 mm x 1 650 mm slab at vertical direction of strand has been established by two-dimensional cutting slice tracing slab solidification heat transfer method

and the calculation for change of shell thickness and temperature field of pipe line steel X80 slab during casting is carried out by ANSYS soft ware. It is obtained that with casting speed 1. 2 m/min the shell thickness of slab at out of mold is 18. 14 mm and the slab liquid core length is 22. 58 m. The relative error of solidification shell thickness between calculated d

ata and measured data is ≤ 2. 5%

and that of terminal position of solidification is 0. 68%. The effect of superheating extent (25 - 55 °C )

casting speed ( 1. 2 -1. 3 m/min) and secondary cooling water rate (79. 2 -96. 8 m

3

/h) on temperature at each point of cutting slice and terminal position of solidification is analyzed. The results show that with increasing casting speed and reducing secondary cooling water rate the slab surface temperature drops slowly

the terminal position of solidification distance from mold is farther and the solidification time is longer. The optimum process parameters for casting slab of pipe line steel X80 are superheating extent 35 ℃

casting speed 1. 2 m/min and secondary cooling water rate 88 m

3

/h.