316L stainless steel is prepared by the production process of 20 t EAF-AOD-LF-casting ingots

and the inclusion content in steel is reduced by LF calcium treatment and bottom argon blowing. The calcium addition amount is determined by a combination of empirical parameters and thermodynamic calculations. The metallographic microscope and scanning electron microscope are used to analyze the effect of ratio coefficient ( actual feeding Ca amount/theory feeding Ca amount) 1.65 and 2. 95 and soft blowing time after LF feeding Ca on ingredient

distribution and size of non-metallic inclusions in steel ingots. The results show that the reasonable ratio coefficient of 316L stainless steel after calcium treatment is about 2. 95. The inclusions in the molten steel after calcium treatment are mainly calcium aluminate compounds and silicate compounds. Extending the soft blowing time had a significant effect on the removal of large-size inclusions ； within 0 ~ 25 min

the quantity and average size of inclusions in the steel ingot reduced with extending soft blowing time and the optimal soft blowing time is 20 min.