Kinetic study on compositional variations of inclusions, steel and slag during refining process

Abstract

A steel-slag-inclusion-alloy-refractory-air multiphase model, which combined the kinetic analysis and the consideration of fluid flow in argon-stirred ladle, was established to investigate the compositional changes during refining process. The steel-slag reaction, the steel and inclusion reaction, the refractory-steel reaction, the refractory dissolution into the slag, the reoxidation of the molten steel, the removal of inclusions by floating, and the alloy dissolution were all considered in the current model. The stirring energy, the average speed of the molten steel in the plume, the horizontal speed of the molten steel in the open eye, the speed of the molten steel near the side wall, the speed of the molten steel at the bottom of the ladle and the volume fraction of the plume were obtained by mathematical simulation. The mass transfer coefficient of the molten steel is obtained by mathematical simulation. Meanwhile, it is assumed that the mass transfer coefficient of inclusions is influenced by the temperature. The calculation results are in accordance with the experimental ones. The influence of different slag compositions, different gas flow rates, and different inclusion diameters on system compositions were also investigated using the current model. It is indicated that the content of T.O. in the molten steel was influenced by the gas flow rate and the removal rate of inclusions goes up with the increasing inclusion diameter.

Effect of Slag Modification on Inclusions in Si–Mn‐Killed 304 Stainless Steels

“…The thermodynamic equilibrium of slag–steel reaction and steel–inclusions reaction are calculated using FactSage with databases of FactPS, FToxid, and FTmisc. [ 28 ]…”

“…The mass transfer coefficient is calculated based on the stirring energy as Equation (2) [ 28 ] and (3). [ 29 ] The slag mass transfer coefficient is expected to be ten times smaller than the mass transfer coefficient in the steel as Equation (4).…”

“…The floatation rate of inclusions is calculated as Equation (5)–(7). [ 28 ] where n is the total inclusion number; H is the depth of the liquid steel, m; Q is the gas flow rate at standard conditions, m 3 s −1 ; α plume is the volume fraction of plume, %; u 0 and u slip are the speed of the molten steel in the plume zone and the steel–inclusion relative velocity, m s −1 .…”

Effect of Sulfur Content on Evolution of Nonmetallic Inclusions in Low Sulfur Al‐Killed Steels during Heat Treatment

“…[4][5][6] The large size calcium aluminate inclusions are responsible for the hydrogen-induced cracking and sulfide stress corrosion cracking of linepipe steels. [7,8] Many technologies were developed to improve the steel cleanliness and control inclusions, such as deoxdation, [9][10][11][12][13][14] slag refining, [15][16][17][18][19][20][21] calcium treatment, [22][23][24][25][26][27] vacuum treatment, [28][29][30][31][32][33] argon blowing, [34][35][36] protective casting, [37][38][39][40][41][42][43] and so on. Especially, calcium treatment was an effective way to modify solid Al 2 O 3 and Al 2 O 3 •MgO inclusions to liquid CaO-Al 2 O 3 inclusions to avoid the nozzle clogging.…”

Modeling of Ladle Refining Process Considering Mixing and Chemical Reaction

“…The predicted inclusion development and compositions of steel and slag agreed well with the industrial practice from 210 and 30 ton ladle treatment. Additionally, similar models were also developed by the researchers with the specified targets due to the high efficiency, [9][10][11][12][13][14][15][16][17] as shown in Table 1. 1) Most researchers used commercial software (FactSage, Metsim, ChemApp, and SimuSage) for thermodynamic calculations, whereas the empirical models offer a faster calculation speed.…”