Formation pathways for MgO·Al2O3 inclusions in iron melt

Mg treatment is conducted in the production of peritectic steel, which greatly reduces the average value of incidence of transverse corner crack in continuous casting slab from 3.10% to 1.06% by 65.8%. In the industrial experiment with the stages of Ar station, before magnesium treatment, after magnesium treatment, and in the slab, the maximum Mg content is 30 ppm after Mg treatment. A large number of Mg containing complex inclusions are formed, and most of Al2O3 are transformed into MgO·Al2O3. In the inclusions, the content of MgO significantly increases from 3.58% to 27.2%. The number density of Mg containing inclusions increases from 45.2 to 168 mm−2. The oxide inclusions smaller than 2 μm account for more than 90%, indicating that Mg treatment can promote the refinement of inclusions. In the slab, most oxide inclusions are transformed into the complex inclusions with Mg containing oxides as the core covered by TiN and sulfide precipitates. These complex inclusions with a size above 1 μm can effectively promote the nucleation and growth of intragranular ferrite to prevent the generation of transverse corner cracks.

[Mg] + 2 [Al] + 4 [O] = MgO \cdot {Al}_{2} {normalO}_{3 (s)}

[Mg] + [O] + {Al}_{2} {normalO}_{3} = MgO \cdot {Al}_{2} {normalO}_{3 (s)}

MgO + 2 [Al] + 3 [O] = MgO \cdot {Al}_{2} {normalO}_{3 (s)}

…”

Section: Resultsmentioning

confidence: 99%

“…Figure 17 shows the formation mechanism of type M complex inclusions. It can be seen from Table 5 that [58,59]…”

Section: Formation Mechanism Of Type M Complex Inclusionsmentioning

confidence: 99%

Characteristics and Evolution of Inclusions in Ti‐Bearing Peritectic Steel with Mg Treatment

Cai

Deng

Yang

et al. 2021

“…For this purpose, many metallurgists performed their experimental studies and theoretical calculations to investigate the formation mechanism and control technology of MgAl 2 O 4 particles in steel. [9][10][11][12][13][14][15][16] Some of them studied the equilibrium relationship among the [Mg], [Al], [O], and MgAl 2 O 4 , and established the phase stability diagram of MgAl 2 O 4 -Al 2 O 3 -MgO to predict their formation condition and phase stability. [9][10][11] Zhang et al [9] calculated the stability diagram of Mg-Al-O system inclusions in molten steel using two methods to predict the formation mechanism of MgAl 2 O 4 inclusions, and suggested that the generation abilities of MgAl 2 O 4 decrease with the temperature increases and the formation region of MgAl 2 O 4 is enlarged as the activity of MgAl 2 O 4 decreases.…”

Section: Introductionmentioning

confidence: 99%

“…Metallurgists also focused on the nucleation pathway of MgAl 2 O 4 inclusions based on the thermodynamic analysis. [12][13][14] Ohta et al [12] suggested that the adding ways of Al and Mg deoxidizers have a strong impact on the formation size of MgAl 2 O 4 inclusions. [12] Later, the present authors calculated the structures and thermodynamic properties of MgAl 2 O 4 metastable phase to study the nucleation pathways of MgAl 2 O 4 in steel, and suggested that the size of MgAl 2 O 4 particle is decided by the formation pathways of MgAl 2 O 4 inclusions in iron melt.…”

Section: Introductionmentioning

confidence: 99%

“…[12] Later, the present authors calculated the structures and thermodynamic properties of MgAl 2 O 4 metastable phase to study the nucleation pathways of MgAl 2 O 4 in steel, and suggested that the size of MgAl 2 O 4 particle is decided by the formation pathways of MgAl 2 O 4 inclusions in iron melt. [14] On the other hand, metallurgists tried to investigate the growth mechanism of MgAl 2 O 4 inclusions in molten steel by kinetics analysis. [15,16] Okuyama et al [15] carried the experiments DOI: 10.1002/srin.202300783…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Cooling Conditions on the Size and Morphology Evolution of MgAl₂O₄ Inclusions in Al‐Deoxidized Steel Coupling with Mg Treatment

Xiao,

Cao,

Wang

et al. 2024

Self Cite

The experiment of Al‐deoxidized steel coupling with Mg treatment is conducted under three cooling methods to observe the size and morphology of MgAl2O4. Most of MgAl2O4 in the water‐cooled steel are sphere or ellipsoid‐like shape, in the furnace‐cooled steel are cubic or octahedral‐like shape, and in the air‐cooled steel are irregular shape. The quantity of inclusions in the size of 1–3 μm increases with the increasing cooling rate, whereas the quantity of the other size decreases with the increasing cooling rate. The result shows that the changing of cooling methods has little effect on the critical size and the nucleation rate of MgAl2O4. The growth of MgAl2O4 is effected by diffusion, Ostwald, and collision growth, and the increasing cooling rate leads to the decreasing growth time. The size of MgAl2O4 is decided by the diffusion of Mg and the growth time of MgAl2O4. Four possible morphological transformation paths of MgAl2O4 in steel are found, and the shape of MgAl2O4 can evolve from sphere or ellipsoid to octahedron via truncated octahedron or cubic‐like shape. The final morphology of MgAl2O4 is controlled by the transformation path which has a close relationship with the cooling rate.

Effect of Magnesium on Sulfide and Microstructure in Microalloyed Steel

Tian,

Liu,

Song

et al. 2024

The effect of Mg on MnS inclusion and the formation mechanism of (Mn,Mg)S‐MgAl2O4 (MA) composite inclusion are analyzed by combining observation for the inclusions in medium microalloyed steel with (and without) 15 ppm Mg, thermodynamics, phase diagram, and crystallography. The addition of magnesium can improve the morphology of inclusions and promote microstructure uniformity. MA is formed by the reaction of dissolved Mg, Al, and O in the Mn‐Mg‐Al‐S‐O liquid melt, while residual Mg is dissolved in MnS, forming (Mn,Mg)S. As the Mg content in the Mn‐Mg‐Al‐S‐O liquid melt increases, the precipitation temperature of the melt increases. Excessive Mg content can lead to a decrease in the proportion of MA in the melt, forming MgO instead of MA. Based on the two‐dimensional slices of MnS and MA, the three‐dimensional morphology can be derived. The lowest mismatch value is 8.00% when the interface is {111} of MnS and {110} of MA.