Commercial Plant Trial of Fluorine Free Mold Flux for Continuous Casting of Blooms

by Yeong-Kang Jung, Hyun-Seok Jung, Jung-Wook Cho, Jeong Hyouk Park

Publisher - POSCO, Korea, Pohang University of Science and Technology, Stollberg & Samil CO., LTD.

Category - General Novel

The bloom caster in Pohang Works, POSCO consists of 8 strands where blooms of 400 x 500 mm in cross section are produced. In order to meet a company’s operating profits goals, the bloom caster must be operated as stable as possible. However, since April 2012 the bloom caster has been at high risk for abrupt ceasing operation due to serious amount of the corrosion at the segments. The main reason of corrosion has been found to be erosion by acidic cooling water. In order to prevent the formation of hydrofluoric acid in cooling water, we applied newly developed fluorine-free mold fluxes to commercial continuous casting of blooms. During 15 trials in the bloom caster, new mold flux without fluorine showed largely the same performance in casting mold as conventional mold fluxes with fluorine: stable mold heat transfer and mold lubrication at normal operation conditions. As expected, secondary cooling became neutral thank to removal of fluorine in mold fluxes. Both the surface and internal quality of cast bloom using fluorine-free mold fluxes were confirmed to be sound by the observation of cast blooms after scarfing and the seam test for wire rods. Since April 2014, nearly 80% of whole production in our bloom caster has been carried out using new fluorine-free mold fluxes.

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