Method for controlling fine inclusions in ultralow-sulfur steel

The invention discloses a method for controlling fine inclusions in ultralow-sulfur steel. The method comprises the steps of primary smelting furnace smelting, LF refining, VD vacuum refining and continuous casting, wherein refining slag is added during station entering of the LF refining, and the adding amount of the refining slag is 10-14 Kg/t steel; and the VD vacuum refining comprises the steps that a steel ladle enters a VD station, deep vacuum pumping, argon bottom blowing and stirring are carried out, and then first soft blowing, calcium wire feeding treatment after vacuum breaking and second soft blowing are carried out, wherein when entering the VD station, the refining slag comprises the following components including, by mass, 55%-60% of CaO, 28%-35% of Al2O3, 5%-10% of MgO, 3%-6% of SiO2, less than 1% of (FeO + MnO), and the balance impurities which have no influence on a slag system; According to the method for controlling the fine inclusions in the ultralow-sulfur steel, the components of the re