Abstract: The metallurgical flow sheet for ultra-low temperature steel 9Ni (/% : 0. 03 ~ 0. 05C, 0. 15 〜0. 30Si, 0. 60 ~0. 70Mn, ≤0, 003P, ≤0. 002S, 9. 0 ~9. 5Ni, 0. 02 ~6. 04Al) is 180t hot metal pretreatment-1801 top and bottom combined blown converter-LF-feeding Si-Ca wire-RH-180 ~250 mm slab casting. With controlling [P] ≤0.001 5% by dephosphorizing in ladle during converter tapping, [S] ≤0. 001% by desulphurizing in LF and controlling [Al] 0. 02% ~ 0. 03% by adding Al bullets and feeding Al wire, RH vacuum ≤200 Pa in feeding silicon-calcium wire process before RH process, controlling [N] ≤25 X 10^-6  and [ H] ≤1. 0 x 10^-6 in ≤200 Pa vacuum for 20 min during RH refining, using electromagnetic stirring, soft reduction and whole shielding casting process, straightening temperature of slab ≥950℃ by increasing casting speed, and slab cooling in slow cooling pit furnace at 300℃ for 40 h, the [ P] , [ S] , [ H] , [ N] and [0] (/10^-6) decrease respectively to 15, 9, 0. 5, 26 and 10, the crack occurring ratio decreases to 0, and the qualified ratio of nondestructive testing is up to 100%.

Key words: Ultra-Low Temperature Steel 9Ni, 180 t BOF-LF-RH-CC Flow Sheet, Production Practice

摘要： 9Ni超低温钢(/%:0.03～0.05C、0.15～0.30Si、0.60～0.70Mn、≤0.003P、≤0.002S、9.0～9.5Ni、0.02～0.04Al)的冶金流程为180 t铁水预处理-180 t复吹转炉-LF-喂硅钙线-RH-180～250 mm板坯连铸。通过转炉出钢时钢包脱磷控制[P]≤0.0015%,LF脱硫使[S]≤0.001%,加铝粒和喂铝线控制[A1]0.02%～0.03%;RH前喂硅钙线RH真空度≤200 Pa,RH处理20 min以控制[N]≤25×10^-6,[H]≤1.0×10^-6;连铸使用电磁搅拌、轻压下和全程保护浇铸工艺,提高铸速使铸坯矫直温度≥950℃,铸坯在300℃缓冷坑40 h,使[P]、[S]、[H]、[N]、[0](/10^-6)分别降至15、9、0.5、26、10,铸坯裂纹率降至0,轧制钢板的无损探伤合格率为100%。

关键词: 9Ni超低温钢, 180t BOF-LF-RH-CC流程, 生产实践