Abstract: Through FactSage thermodynamics software calculation and laboratory 25 kg vaccum-induction furnace smelting of BT700L automobile beam steel, the influence law of refining slag on the alloying of niobium and titanium is discussed and the effect of the addition of rare earth niobium-titanium composite alloy on steel structure, inclusions and precipitates is studied. The results show that the 55% CaO -25% Al₂O₃ ~ 15%SiO₂ ~5% MgO refining slag with a basicity of 3. 7 is more suitable for the smelting of BT700L automobile beam steel. After the refining slag added, Ti in the molten steel reacts with SiO₂ in the slag, Si is reduced into the steel, the Ti content in the steel decreases, and the Si content increases ； The cast structure of the experimental steel is composed of ferrite and a small amount of bainite ； The addition of rare earths reduces the number and size of inclusions in the steel, and makes the precipitates in the steel more dispersed and finer.

摘要： 通过FactSage热力学软件计算和实验室25 kg真空感应炉冶炼BT700L汽车大梁钢，探讨精炼渣对馄 钛合金化的影响规律，并研究稀土貿钛复合合金的加入对钢组织、夹杂物、析出物的影响。结果表明,55%CaO~ 25%Al₂O₃ ~ 15%SiO₂ ~5%MgO,碱度为3.7的精炼渣更加适合BT700L汽车大梁钢的冶炼。添加该精炼渣后，钢水中的Ti和渣中的SiO₂反应,Si被还原进入钢中，钢中Ti含量减少,Si含最提高;实验钢的铸态组织由铁素体和少量贝氏体组成;稀土的加入降低了钢中夹杂物的数量和尺寸，并使钢中析出物更加弥散细小。