Abstract: This article presents the smelting practice of 9Ni steel for ultra-low-temperature pressure vessel in a certain steel plant by the "BOF → LF → scraping slag/fetching slag → LF → VD → CC" process. The decarburization and desulfurization in the BOF + LF process require that the steel produced by the converter has a low phosphorus （w［P］） ≤ 0.009%） and carbon content （w［C］） ≤ 0.05%）， with an average desulfurization rate of 74.3% and an average decarburization rate of 51.2%. The control of phosphorus content is more difficult than carbon content in the production process. In the scraping slag process， the average phosphorus reversion rate in the molten steel is 16.89%， while in the fetching slag process， it is 22.61%. Although the scraping slag process results in a lower phosphorus reversion rate in the molten steel， the processing time is increased by 15 to 20 minutes， and the average molten steel loss is increased by 3.1 t per heat. After adjusting the addition of nickel plates from the converter to the ladle furnace， the average nickel recovery rate increases by 3.74%. Through optimizing the production process， the molten steel in the tundish meets internal control requirements for phosphorus（ P）， sulfur （S）， nitrogen N， total oxygen （T.O）， and carbon （C）， ensuring high purity of the molten steel， the macrostructure center segregation of the cast slab reaches 1.0～1.5 grade in class C， the internal and surface quality of the cast slab are good. The rolled steel plate exhibits excellent performance at -196 ℃.

Key words: 9Ni Steel, Dephosphorization； Decarbonization； Scraping slag； Fetching Slag

摘要： 介绍了某钢厂采用120 t转炉→LF炉→扒渣/捞渣→LF炉→VD炉→板坯连铸工艺生产超低温压力容器用9Ni钢的冶炼实践情况，采用转炉+LF炉脱碳脱磷工艺，控制转炉出钢w［P］≤0.009%、w［C］≤0.05%，炉后平均脱P率74.3%，平均脱碳率51.2%，生产过程中，P的控制难度相比C的控制难度大。采用扒渣工艺下钢水的平均返磷率为16.89%，而捞渣工艺下钢水的平均返磷率为22.61%，扒渣工艺下钢水的返磷率低，但生产节奏长15～20 min，钢水重量损失平均增加3.1 t/炉。镍板由转炉废钢槽加入调整为全部由LF炉加入后，Ni平均收得率提高了3.74%。通过对生产工艺的优化，中间包钢水P、S、N、T.O、C满足内控要求，钢水纯净度高，铸坯低倍中心偏析达到C类1.0～1.5级，表面质量良好，轧制钢板在-196 ℃下性能优良。

关键词: 9Ni钢, 脱磷, 脱碳, 扒渣, 捞渣