Deoxidation behavior of rare earth ferrosilicon and evolution mechanism of inclusions in high-cleanliness Q195L steel for cold rolling

Aiming at the problem that large-sized angular Al 2 O 3 inclusions are easily formed in the traditional pure aluminum deoxidation process for Q195L low-carbon killed steel, industrial production tests were carried out using rare earth ferrosilicon instead of pure aluminum for deoxidation. Based on the 240 t converter-Ladle Furnace refining-continuous casting production line of a domestic steel plant, an aluminum deoxidation control group and a rare earth ferrosilicon deoxidation experimental group were set up. Analyzed using various testing methods including oxygen-nitrogen-hydrogen analysis, ICP-MS, and scanning electron microscopy. The results show that rare earth ferrosilicon deoxidation can achieve a deep deoxidation effect equivalent to that of pure aluminum, with the total oxygen content of rolled products reduced to 16 ppm. The total rare earth content in molten steel at the refining station reaches 64 ppm, corresponding to a rare earth yield of 12.05%. Compared with aluminum deoxidation in the control group, rare earth ferrosilicon deoxidation generates near-spherical rare earth-silicon-oxygen composite inclusions, which significantly reduces the number density of inclusions in the early stage of smelting. The size distribution of inclusions in the final rolled products is comparable to that of the control group. This study clarifies the whole-process evolution path of inclusions in the rare earth ferrosilicon deoxidation system, verifies the technical feasibility of this process in the industrial production of Q195L steel, and provides a theoretical basis and industrial practice reference for the high-quality smelting of low-carbon killed steels.