70t BOF-LF-VD-CC流程转炉钢氮含量控制的工艺实践

Practice of Process for Control of Nitrogen Content in Converter Steel Melting by 70t BOF-LF-VD-CC Flow Sheet

炼钢厂冶炼20CrMnTi,45,40Cr,GCr15钢的生产流程为70 t BOF-LF-VD-220 mm×220 mm CC工艺。由22炉20CrMnTi,40Cr和45钢中氮含量分析得出转炉出钢后钢中平均氮含量-[N]为21.70×10^(-6),LF精炼后平均[N]48.95×10^(-6),中间包平均[N]63.62×10^(-6)。通过将铁水比从85%提高到92.3%,控制转炉终点[P]≤0.008%,出钢前钢包充氩,LF精炼快速形成泡沫渣,渣层厚100~120 mm,防止钢水吸氮,连铸时采用长水口控制吹氩量等措施,6炉GCr15钢冶炼结果表明,LF精炼后[N]为51.8×10^(-6)~60.2×10^(-6),VD后[N]29.1×10^(-6)~33.9×10^(-6),钢材中氮含量为31.8×10^(-6)~40.0×10^(-6),满足用户对钢材冷加工的需要。

The flow sheet for steelmaking steel 20CrMnTi, 0.45C, 40Cr and GCr15 at melting shop is 70 t BOF-LF- VD-220 mm x 220 mm CC process. It is obtained by analysis of 22 heats of steel 20CrMnTi, 40Cr and 0. 45C that the aver age nitrogen content in steel after BOF tapping- [ N] is 21.70 x 10-6, end LF refining the average [ N]48.95- 10 -6 and in tundish the average [ N63.62 - 10-6. With increasing hot metal ratio from original 85% to 92. 3% , controlling BOF end [ P] 〈0. 008% , ladle filling argon before tapping, quick forming foamed slag in LF refining with slag thickness 100 120 mm to prevent liquid absorbing nitrogen, using long nozzle and controlling argon blowing rate, the results by melting 6 heats of steel GCrl5 show that the [ N] at end LF refining is 51.8 - 10-6 -60. 2 -10-6, the [ N] at end VD is 29. 1- 10 -6 - 33.9 - 10 -6, and the nitrogen content in products is 31.8 x 10 -6 -40. 0 x 10 -6, all products meet the requirement for cold working.