Abstract: In present study, formation of inclusions in high quality saw wires were discussed in details by systematical samples in pilot trials. It was found that inclusions have readily located in the lower melting point regions of MnO-SiO₂-Al₂O₃ and CaO-SiO₂-Al₂O₃ ternary systems. The former type of inclusions was endogenous ones originated from the chemical reactions between liquid steel and the Si-Mn deoxidation products. While the latter was caused by the entrapment and the following emulsion the of top slag particles into molten steel. During the solidification of liquid steel in continuous casting, silica content in the formed MnO-SiO₂-Al₂O₃ in secondary refining showed an obvious increase, resulted in the precipitation of pure SiO2 phase in the inclusion matrix. Because of the differences in deformability, the newly produced dual-phased inclusions would be gradually separated from each other in the following multi-pass rolling. Therefore, SiO₂ based inclusions singularly existed in the steel can be frequently observed in the rolled coils. However, it was impressive that those SiO₂based inclusions was changed into very tiny dotshaped particles dispersed along the rolling direction. Particularly, the coil was continuously drawn to 29 602 km without fracture despite the existence of the SiO₂based inclusions. Therefore, it was concluded that there was no need to emphasize on the targeting of lower melting point of inclusions for saw wires. Instead, systematic optimization of the whole process and size minimization of inclusions were considered to be more important.

Key words: saw wire, inclusion, composition, morphology, thickness