The production flowsheet for developed casting round bloom of steel P11 (/% : 0. 08 ~ 0. 14C

0. 65 ~ 0. 85Si

0. 40 ~0. 60Mn

≤0. 010P

≤0. 010S

1. 10 ~ 1. 30Cr

0. 46 -0. 60Mo

≤0. 015Alt) is KR metal pretreatment- 70 t top and bottom combined blown converter- LF- VD- round bloom casting process. With using the measures including controlling the elements content /% : 0. 09 ~ 0. 11C

1.15~1. 20Cr

0. 07 ~ 0. 08P

0. 002 ~ 0. 005S and 0. 008 ~ 0. 015Als

controlling tundish liquid temperature (1538 ±5) ℃

casting speed 0. 70 ~ 1. 05 m/min

secondary cooling water ratio 0. 35 ~0. 40 L/kg

strengthening temperature ≥900 °C and temperature of slow cooling pit furnace ≥500 ℃，the examination results show that the surface quality of casting bloom is qualified with rating of shrinkage cavity ≤0. 5 and rating of central porosity ≤1. 0

the P content in steel is 0. 007% ~ 0. 008% and the S content in steel is 0. 002% ~ 0. 005%

so the steel has better flowing accelerating corrosion (FAC) resistance at service temperature.