Abstract: Quality requirement for 350 km/h high-speed rail steel is total oxygen content in steel- T[O] ≤20 x 10^-6, and B, C and D series inclusions rating ≤1.0. In domestic heavy rail steel steelmaking process, it is normally to using non-aluminium deoxidation process, i. e. intensifying deoxidation by using SiCaBa alloy to form low melting point Mn-Al-Si- Ba-Ca multicomponent oxide inclusions which all remove from liquid during refining process. The behavior of inclusions in rail steel U71MnG steelmaking by hot metal desulphurization pretreatment-150 t top and bottom combined blowing convert- er-LF-VD-280 mm x 380 mm CC flow sheet is studied, including the ingredient and characteristics of oxide inclusions in rail steel steelmaking by non-aluminium deoxidation process, the effect of converter end [C] on oxygen activity of liquid and the effect of basicity of LF refining slag and soft argon stirring process in later period of VD process on inclusions and oxygen content in steel. It is obtained that the ≤20 μm oxide inclusions in head of rail is seconadry deoxidation products during refining process, with controlling converter end [C] ＞0.15% , controlling basicity of refining slag- (CaO)/(SiO₂) =2.5-3 and S (FeO + MnO) ≤1.0% , it is available to decrease the quantity and size o£ oxides in rail steel.

Key words: 150 t BOF-LF-VD-CC Flow Sheet, High-Speed Rail Steel, Non-Aluminium Deoxidation, Inclusions

摘要： 时速350 km高速钢轨要求钢中全氧含量T[O]≤20×10^-6,非金属夹杂物B、C、D类≤1.0级。国内在重轨钢冶炼中,通常采用无铝脱氧工艺,即采用SiCaBa合金强化脱氧,形成了低熔点的Mn-Al-Si-Ba-Ca多元型氧化物夹杂,该类夹杂物在精炼中全部排出钢液。研究了铁水预处理脱硫-150 t顶底复吹转炉-LF-VD-280 mm ×380 mm连铸流程冶炼钢轨钢U71MnG时的夹杂物行为,包括无铝脱氧工艺钢轨钢中氧化物夹杂的组成及特征,转炉终点[C]对钢水氧活度的影响以及LF精炼渣碱度和VD后期软吹氩搅拌对钢氧含量和夹杂物的影响。结果得出,钢轨头部的≤20μm氧化物夹杂为精炼时二次脱氧产物,通过控制转炉终点[C]＞0.15%,控制精炼渣碱度(CaO)/(SiO₂)=2.5~3,∑(FeO+MnO)≤1.0%可有效降低钢轨钢中氧化物的数量和尺寸。

关键词: 150 t BOF-LF-VD-CC流程, 高速钢轨钢, 无铝脱氧, 夹杂物