≥ 25 min)-argon shield 1.52 t ingot-casting- ingot homogenization treated at (1250 ± 10) ℃ for 15h-forging billet Φ140 mm at 780 -810℃ forging to Φ110 mm-full annealing. The chemical constituents satisfied the technical requirements
oxygen content in forgings 12.0 x 10
-6
~ 13. 5 x 10
-6
non-metallic inclusions rating≤1
rating of banded structure is 2
austenitic grain scale is 8.5
and mechanical properties test satisfiy the technical requirements.