The variations of a non-metallic inclusion during the refining proceae of 6 ton basic arc-furnace in the case of high carbon chromium steel (C0.85-1.10%, Cr1.0-1.8%) were mea-sured by microecopic method. As the result, it was recognized that the inclusion is observed under the microscope having the remarkable influence with the refining conditions. This report indicated the refining conditions to make the cleaner steel of high carbon chromium steel.
Rather profitable refining conditions for the reduction of non-metallic incluaions are as follows:
1) Fit time of oxidizing Period is about 75-85min.
2) Fit killing time at the first of reducting period is about 50-60min.
3) Necessary time of total refining is at least 3 hours.
4) Necessary decarbonizing amount at the oxidizing period is about 0.5-0.6 per cent.
5) Necessasy carbon content in the last of oxidizing period is about 0.55-0.65 per cent.
6) Accordingly, carbon amount at the melt-down period must be raised about 1.05-1.25 per cent.
7) Decarbonizing velocity must be about 0.006C%/min.
8) Fit amouut of ore used is about 40-55kg per ton.
9) Silicon content in the charging materials muat be as less as possible.
10) Manganese and chromium content in the charging materials must be kept up largely.
11) Basicity of slag at the middle of reducting period must be kept in the following ranges. (CaO)/(SiO
2)=about 61-63%/about 17-19%=about 3.1-3.5.
12) Aiter all, it is most important for the cleaner steel to reduce the non-metallic inclusion at the oxidizing period and the killing period at the first of the reducting period as fast as possible.
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