Laboratory Study on Evolution Mechanisms of Non-metallic Inclusions in High Strength Alloyed Steel Refined by High Basicity Slag

Factors to Determine Inclusion Compositions in Molten Steel during the Secondary Refining Process of Case-Hardening Steel

“…The thermodynamic calculations showed that 7) Jiang et al 12) and Deng et al 15) reported that under the condition of the higher Mg activity rather than Ca, the evolution occurs in the sequence of under the present conditions. The calculations to obtain the activity coefficients of the components were carried out by using the values shown in Table 3.…”

“…3,9) In addition to the above studies, a number of researchers have conducted work on the inclusion evolutions in detail including the variations from Al 2 O 3 to the CaO-Al 2 O 3 system, 6) from Al 2 O 3 to MgO·Al 2 O 3 or partially to MgO, [7][8][9][10] and from MgO·Al 2 O 3 to the CaO-Al 2 O 3 system or to the CaO-MgO-Al 2 O 3 system. [11][12][13][14][15][16][17][18] It should be pointed out that most of researches stated above were done in laboratory scales. Thus, information about inclusion formation in practice is still lacking to understand inclusion evolution occurring in the practical refining stages.…”

“…[6][7][8][9][10][11][12][13][14][15][16][17][18] Discussion in the following sections focuses on how each phenomenon is related to the variation at each process based on the thermodynamic calculation results. 39) Another cause could be the slag entrapment caused by the gas stirring.…”

“…It was reported that both MgO·Al 2 O 3 and the CaO-Al 2 O 3 system inclusions were detected in the refining stages of Al-killed steels. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] According to the report, MgO·Al 2 O 3 inclusions have the potential to cause nozzle clogging due to its high sinterability because they are stable with a solid state at the steelmaking temperatures.…”

“…16) In the following, the condition for the inclusion change of Al 2 O 3 →CaO-Al 2 O 3 is proposed by comparing the previous studies. 7,8,12,[15][16][17][18] The Ca contents were compared to estimate the condition because it was very difficult to compare the activities of Ca because their experimental situations were very different from each other. Some were for carbon steels and tool steels, while some were for stainless steels.…”