熔鋼中の非金屬介在物に及ぼすクロムの作用に就て(II)

Abstract

The foregoing statement reported that the ferro-chromium addition in the last period of refining at the basic arc furnace melting, caused a conspicuous decrease of non-metallic inclusion in molten steel, and proved the chromium to be one of the strong cleansers.Ever since, the following results have been obtained by further examinations in the same field by means of basic and acid open-hearth meltings.(1) With basic open-hearth melting, the addition caused sometimes the increase and sometimes the decrease of inclusion.(2) With acid open-hearth melting, the inclusion usually increased.(3) It was found that the increase and decrease of inclusion were closely related with the basicity of slags. Namely, with the basic open-hearth melting, in case of the CaO/SiO2 is less than about 2.0-2.2 or the ΣRo/SiO2 is less than about 2.8-3.0, the inclusion increases, and when it is more than the figure the inclusion decreases. This, eventually, induces the fact, that in the acid open-hearth melting, the inclusion duly increases instead of decreasing, and as explained above, it increased without exception.(4) After comparative studies between basic arc furnace melting above described and basic open-hearth melting, the above relation proved to be so relative that, when the slag is basic, and in the range around about 2.0-4.5 of basicity (CaO/SiO2), the addition of ferro-chromium decreases the inclusion, and the maximum decreasing ratio can be reached at the basicity about 2.6-3.0 in both cases.