Abstract: To design a reasonal composition of converter slag and achieve a satisfactory dephosphorization ratio， the structures of CaO-SiO₂-Fe_○xO-P₂O₅ molten slags were examined by Raman spectroscopy， and the existence form and transformation behavior of phosphorus were further analyzed in terms of the variation of slag composition during the process of basic oxygen steelmaking. The results show that phosphorus in molten slags mainly exists in the forms of Q⁰(P)， Q¹(P) and Q²(P). Meanwhile， phosphorus can enter the silica tetrahedron and ferrite tetrahedron， and occupy the locations of silicon and iron to form the Si—O—P and Fe—O—P bonds， respectively. With the increasing total content of CaO and FeO， the molar fractions of the Q⁰(P)， Q¹(P)， Q⁰(Si) and Q¹(Si) with lower-degree polymerization increase， while the molar fractions of Q²(P)， Q²(Si) and Q³(Si) with higher-degree one decrease. In addition， Si—O—P and Fe—O—P bonds also gradually decrease. The Si—O—P and Fe—O—P bonds disappear， when the basicity of molten slag was 2.83.

Key words: converter slag; Raman spectra; melt structure; transformation behavior; phosphorus