Control of Formation of Spinel Inclusion in Type 304 Stainless Steel by Slag Composition

Control of MgO·Al2O3 Spinel Inclusions in Stainless Steels

“…At first, slag entrainment takes place in an AOD converter due to its vigorous stirring by Ar gas after Cr reduction. 17,18,26,[34][35][36][37] For stainless steel 26,36,37) stated that this tendency is enhanced with a decrease in temperature. Similar tendency is reported by the other researcher.…”

“…(17) is not only approximately 1 wt% of Al contained in ferrosilicon alloys but bricks containing alumina also. 36,37) If alumina content exceeds the critical condition of the formation of spinel, they precipitate in aluminosilicate inclusions. The critical condition can be estimated thermodynamically by the following reaction.…”

Thermodynamic Model for Prediction of Slag-Steel-Inclusion Reactions of 304 Stainless Steels

“…5) Typically, the CaO-SiO 2 -Al 2 O 3 -MgOCaF 2 slag is used to lower [Al] s in steel and suppress the formation of the Al 2 O 3 -MgO in inclusions. 12,17) In the current study, the CaO-SiO 2 -Al 2 O 3 -MgO-CaF 2 slag was optimized using the current thermodynamic model to lower the Al 2 O 3 -MgO in inclusions at 1 873 K and decrease the melting temperature of inclusions in Si-Mn-killed 304 stainless steels. The compositions of the initial Si-Mn-killed 304 stainless steel and inclusions in the calculations are given in Tables 2 and 3.…”

“…1,2) Non-metallic inclusions in steel have a detrimental effect on the performance of steels, such as their strength, toughness, fatigability, cleanliness, surface finishing, etc. 3) A wide range of operating approaches including deoxidation, 4,5) calcium treatment, [6][7][8][9][10][11] slag refining, [12][13][14][15][16][17] and prevention against reoxidation [18][19][20][21] are applied throughout the steelmaking processes of stainless steels. Inclusion composition is greatly influenced by the composition of the top slag and the refractory material.…”

“…[12][13][14][15][16][17]23,24) A large number of thermodynamic models based on thermodynamic and phase equilibrium data for a given system has been developed, 25) which can be used to predict the relationship between compositions of slag, steel, and inclusions in relatively simple systems, such as Al-O, [26][27][28] AlMg-O, [29][30][31] Al-Ca-O, [32][33][34] Al-Ti-O, [35][36][37] Al-Si-Ca-O, 38,39) Al-Si-Mn-O, [40][41][42] etc. However, the thermodynamic models can hardly be applied to a multicomponent system due to complicated calculations and lack of thermodynamic data.…”