120 t BOF-LF-RH-CC流程冶炼石油套管钢时TiN的析出和控制

石油套管用钢(/%:0.26~0.29C，0.25~0.35Si，0.40~0.50Mn，≤0.009P，≤0.004S，0.95~1.05Cr，0.09~0.11V，0.02~0.04Al，0.015~0.020Ti，≤0.0060N)的生产流程为铁水预处理-120 t BOF-吹氩-LF-喂CaSi线-RH-合金化-喂CaSi线-软吹氩-Φ220 mm圆坯连铸工艺。通过热力学分析得出钢中N含量超过50×10^-6以及工业试验得出生产的圆铸坯中的N含量为67×10^-6时,在铸坯中易形成2μm以上的TiN夹杂。通过控制BOF终点N]≤30×10^-6,LF终点S]≤25×10^-6,O]≤25×10^-6,N]≤35×10^-6,RH合金化后终点N]≤35×10^-6,H]≤1.5×10^-6,稳定喂CaSi线速度300~400 m/min,控制中间包N]≤40×10^-6,严格连铸保护浇铸工艺,则铸坯中的N含量≤50×10^-6,钢中TiN夹杂数量显著下降,未发现大尺寸TiN夹杂物。

Precipitation and Control of Titanium Nitride in Oil Casing Tube Steel Steelmaking by 120 t BOF-LF-RH-CC Flow Sheet

The production flow sheet for oil casing tube steel (/% ： 0.26-0.29C, 0.25-0.35Si, 0.40-0.50Mn, ≤0.009P, ≤0.004S, 0.95-1.05Cr, 0.09-0.11V, 0.02-0.04Al, 0.015-0.020Ti, ≤0.0060N) is hot metal pretreatment-120 t BOF-argon blowing-LF-CaSi wire feeding-RH-Alloying-CaSi wire feeding-soft argon blowing-Φ200 mm round bloom casting process. By commercial test as the N content in produced round casting bloom is 67 x 10^-6 and by thermodynamic analysis as the N content in steel is more than 50 x 10^-6, the more than 2 μm TiN inclusions easily form in casting bloom. With controlling BOF end N] ≤ 30 X 10^-6, LF end S] ≤ 25 X 10^-6 , O] ≤ 25 X 10^-6 and N] ≤ 35 X 10^-6, after alloying RH end N] ≤ 35 x 10^-6 and H] ≤ 1.5 x 10^-6, stably feeding CaSi wire speed 300-400 m/min and controlling tundish N] ≤ 40 x 10^-6 and strict casting-shielding process, the N content in casting bloom shall be ≤ 50 X 10^-6, the amount of TiN inclusions in steel decreases markedly and there are not larger size TiN inclusions to be found in steel.