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% Al

2

O

3

~ 15%SiO

2

~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 SiO

2

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 b

ainite ； 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.