Production technology for super high cleanliness of ultra-thick steel plate

Abstract The technology for producing ultra-clean steel by the process of “KR-BOF-LF-VD-CC” was developed. Sulfur was efficiently reduced to less than 5 ppm by the LF-VD process. Phosphorus was stably removed to less than 20 ppm by optimizing the composition of dephosphorization slag in the converter. The [N] and [H] were reduced to less than 20ppm and 1.0ppm after the perfect combination of vacuum degree and vacuum treatment time during the VD process. T.[O] was controlled to less than 5ppm by the technology of precise controlling of inclusion composition and efficient removal. Industrial production results showed that the average content of [S]+[P]+[O]+[N])+[H] was 42.3 ppm and the lowest was 34.7 ppm.