MgO In Slag Research Articles

Effect of MgO Content and CaO/Al2O3 Ratio of CaF2–CaO–Al2O3–MgO Slag on the Oxidation Behavior of Mg in Mg-Containing GH3128 Alloy

Effect of MgO Content and CaO/Al2O3 Ratio of CaF2–CaO–Al2O3–MgO Slag on the Oxidation Behavior of Mg in Mg-Containing GH3128 Alloy

Deep learning revealed statistics of the MgO particles dissolution rate in a CaO–Al2O3–SiO2–MgO slag

Accelerated material development for refractory ceramics triggers possibilities in context to enhanced energy efficiency for industrial processes. Here, the gathering of comprehensive material data is essential. High temperature-confocal laser scanning microscopy (HT-CLSM) displays a highly suitable in-situ method to study the underlying dissolution kinetics in the slag over time. A major drawback concerns the efficient and accurate processing of the collected image data. Here, we introduce an attention encoder–decoder convolutional neural network enabling the fully automated evaluation of the particle dissolution rate with a precision of 99.1%. The presented approach provides accurate and efficient analysis capabilities with high statistical gain and is highly resilient to image quality changes. The prediction model allows an automated diameter evaluation of the MgO particles' dissolution in the silicate slag for different temperature settings and various HT-CLSM data sets. Moreover, it is not limited to HT-CLSM image data and can be applied to various domains.

Effect of MgO content and CaO/Al2O3 ratio on melting temperature and viscosity of CaF2–CaO–Al2O3–MgO slag for electroslag remelting

During electroslag remelting (ESR), high MgO contents are typically added to CaF2–CaO–Al2O3 slag to control magnesium content in iron- and nickel-based alloys. The melting temperature and viscosity of ESR slag are pivotal for energy consumption, production efficiency, smooth operation, and ingot quality. However, there is currently a notable scarcity of research on the melting temperature and viscosity of CaF2–CaO–Al2O3–MgO slag with high MgO levels. Thus, the melting temperatures and viscosity of CaF2–CaO–Al2O3–MgO slags with varying MgO contents and CaO/Al2O3 (C/A) ratios were investigated. The results show that as the MgO content increases from 7.83 % to 13.18 %, the final precipitation content of the MgO phase significantly increases, resulting in an increase in the melting temperature from 1306 °C to 1319 °C. With the increase in the C/A ratio from 0.86 to 1.16, the precipitation completion temperatures of the Ca12Al14F2O32 and MgO phases significantly decrease and the MgAl2O4 phase transforms into the CaO phase. Hence, the melting temperature decreases from 1329 °C to 1314 °C. Further increasing the C/A ratio to 1.40, the final precipitation content of the CaO phase increases, resulting in a decrease in the melting temperature from 1314 °C to 1282 °C. Moreover, as the MgO content and C/A ratio increase, the slag viscosity exhibits different change trends within various temperature ranges. This depends on which of the depolymerization of the slag structure and the precipitation and clustering of the MgO phase has a greater effect on the slag viscosity.

Experimental, analytical, and numerical quantification of the Marangoni effect in static refractory finger test

This study investigated the local corrosion of alumina and magnesia refractory in CaO–Al2O3–SiO2–MgO slag due to the Marangoni effect, which is a key factor for localized wear in different industrial processes, using experimental, analytical, and numerical approaches. The objective is to explore the Marangoni effect using computational fluid dynamics simulation aiming to provide insights into the dominant slag flow patterns influencing refractory corrosion and to determine whether the observed corrosion groove can be attributed solely to the Marangoni effect. Static finger tests were conducted at temperatures of 1500 and 1550 °C employing a continuous wear testing device. A two-dimensional axisymmetrical section model of the test assembly was created, incorporating concentration-dependent surface tension gradients and surface tension forces to replicate the Marangoni flow. As the surface-tension simulation required time steps in the order of 10−5 s, modeling up to the experimental time scale cannot be realized. Consequently, the simulation outcomes were extrapolated to anticipate the groove radii of the experimental corrosion steps. Corrosion rates were derived from measurements and analytical methodologies. Established analytical equations for corrosion under surface-tension-flows were adapted to enhance the accuracy of corrosion rate estimation. However, the analytical considerations yielded poor estimates. Meanwhile, the employed simulation model successfully generated plausible predictions of the Marangoni flow. Drawing from the extrapolated simulation outcomes, the projected groove radii exhibited a close correspondence to the measured values, demonstrating a relative error of approximately 3 %, 11 %, and 15 % for the magnesia system at 1500 °C and alumina systems at 1500 and 1550 °C, respectively. Taking into account the uncertainties inherent in the methodological approach, the disparities in the alumina values suggest the involvement of mechanisms beyond the Marangoni effect in the localized wear. Consequently, this study effectively clarifies the impact of the Marangoni effect on the local wear of the examined material systems.

Thermodynamics of Palladium Dissolution Behavior in FetO–SiO2–CaO–Al2O3–MgO Slag at 1873 K

Thermodynamics of Palladium Dissolution Behavior in FetO–SiO2–CaO–Al2O3–MgO Slag at 1873 K

Effect of Al2O3 and CaO/SiO2 ratio in slag on the cleanliness of bearing steel GCr15

This study investigates the effect of Al2O3 content (ranging from 30% to 38%) and the CaO/SiO2 ratio (ranging from 4 to 7) in LF refining slag at 1600 °C on the cleanliness of bearing steel through laboratory experiments. The driving forces (concentration difference ΔC) of four inclusions (Al2O3, MgO-Al2O3, Mg4Al2O7, and MgO) in the CaO-SiO2-Al2O3-5% MgO slag as well as the slag viscosity (η) at 1600 °C were calculated by Factsage 8.1 software. The relationship between ΔC/η (specifically for MgO·Al2O3 inclusions) and the cleanliness of bearing steel was investigated. The results show that the steel-slag reaction significantly reduces the total oxygen content, inclusion number density, and area fraction within the molten steel, thereby augmenting its cleanliness. With increasing Al2O3 content and CaO/SiO2 ratio in the slag, a notable trend of initial decline followed by subsequent increase is observed in both total oxygen content and total inclusion number density and area fraction within the molten steel. The LF slag composition is suggested to comprise 32% Al2O3, with a CaO/SiO2 ratio of 6. The ΔC/η ratio of MgO·Al2O3 inclusions shows a positive correlation with the apparent rate constant of oxygen removal (ko) while exhibiting a negative correlation with both the number density and area fraction of MgO·Al2O3 inclusions. This indicates that ΔC/η ratio of MgO·Al2O3 inclusions directly affects the removal rate of MgO·Al2O3 inclusions. Moreover, LF refining slag exhibits varying adsorption capacities for the four types of inclusions, ranked as Al2O3 > MgAl2O4 > Mg4Al2O7 > MgO.

M100 concrete probing on quinary cementitious matrix incorporated with industrial ferrochrome slag sand

The potential exploration of micro (10−6) and nano (10−9) sized binders and Ferrochrome slag sand (FSS) is supplanted and discussed in the M100 concrete. Supplementary Cementitious Materials (SCM) and FSS are supplanted in concrete to sustain and minimize the exploitation of resources. The clinker products are diminished by replacing SCM like Metakaolin (MK) of 8, 10, and 12% and Nanosilica (NS) of 0.5, 1 and 1.5%. Besides, the FSS (10, 20, 30, 40, 50, and 100%) is incorporated in the place of crushed sand (Csand). The in-depth material characterization demonstrates the shape, micro texture, and elemental analysis. The optimum mix (F4) has a compressive strength of 126.08 N/mm2 at 28 days. The densely hydrated cluster (CSH(H&L)) in the F4 mix are an intellectual cause of strength gain. The microstructure with Hadley grain (Peeling bark) in the F10 mix is a root for the strength degradation. The MgO in slag escalates the strength at 365 days. The Packing action of SCM and FSS are schematized. The TGA plot of the F4 mix has a significant (−9.34%) silicate hydrate peak than referral concrete (RC). The Global warming potential (GWP) of the F4 mix saves 12.96% emission of CO2 than RC.

Experimental Study on MgO-Na2CO3 Combined Excitation Recycled Fine-Powder-Slag Cementitious System and Modification

The hydration mechanism and strength development of alkaline salt-activated cementitious materials primarily rely on the alkaline activators and mineral admixtures employed. However, the impact of increased Mg2+, Al3+, and Si4+ resulting from the addition of MgO and steel slag (SS) on the hydration mechanism of these systems remains undetermined. This study delves into the hydration mechanism and mechanical properties of a Na2CO3-MgO-activated regenerated micropowder-slag-based cementitious material system. Mechanical properties were assessed by measuring dry shrinkage and compressive strength at various ages, up to 28 days. The reaction mechanism was scrutinized using X-ray diffraction and a thermogravimetric analysis. The main reaction products contributing to the strength development are C-S-H, C-(A)-S-H gel, and hydrotalcite. Other carbonate-containing phases make smaller contributions. The findings reveal that when SS usage is at 10%, it yields higher early strength compared to ordinary samples. Samples incorporating MgO and SS achieved strengths similar to or surpassing those of the control samples. A noteworthy observation is the synergistic excitation effect between sodium carbonate (NC) and MgO, leading to the generation of a significant amount of gelling substances. These substances fill the pores of the structure, resulting in the formation of a dense microstructure. Consequently, the enhanced interaction between NC and MgO contributes to the overall strength development of the cementitious material.

Dissolution mechanism and computational model for controlling dissolution rate of alumina particles in CaO–SiO2–Al2O3–MgO slag

In present study, a high-efficiency CaO–SiO2–Al2O3–MgO slag was designed to dissolve alumina particles, and the in situ observation for alumina particles dissolution by CSLM instrument equipped with color fast CCD camera was conducted, which broke through the limitations of the original CSLM equipment. The dynamic measurements showed that the dissolution behavior of alumina particles was controlled by diffusion. Moreover, the mechanism of dissolution of alumina particles was illustrated by combining SEM-EDS detection and thermodynamic calculations. It was found that there was an about 3 μm distinct interface layer when alumina particles were dissolved in slag, and the formation order of products of the interface layer was closely related to its thermodynamics. In addition, the apparent activation energy of reaction between Al2O3 and CaO was used to calculate the reaction time of alumina particles with different particle size, and the viscosity values of the all slags obtained by the Factsage 8.2 thermodynamic software and Stocks-Einstein theory were used to calculate the time required for diffusion of alumina particles with different particle sizes. Compared the total time of chemical reaction and the diffusion mass transfer, it is found that when the radius of alumina particles is greater than 2.5 μm, the dissolutions of alumina particles in all CaO–SiO2–Al2O3–MgO slag composition points are controlled by diffusion.

Evolution Behavior of Non-metallic Inclusions in High-Al or Si-Alloyed Steel Reacting With CaO–Al2O3–FeO–SiO2–MgO Slag

Evolution Behavior of Non-metallic Inclusions in High-Al or Si-Alloyed Steel Reacting With CaO–Al2O3–FeO–SiO2–MgO Slag

Effect of MgO on phase equilibria of copper matte and SiO2-saturated iron silicate slag in smelting complicated copper resources

The effect of MgO on the phase equilibria between matte and tridymite-saturated FeOx−SiO2−MgO slag was investigatedusing high-temperature equilibration and microanalysis technique. The results showed that at 1300 °C and p(SO2) of 10 kPa, the presence of MgO reduced the FeO activity of the slag, leading to the decrease in the oxygen partial pressure (p(O2)) over the slag and the Cu solubility in the slag. Due to the lower FeO activity, FeS was oxidized from matte into slag, increasing the Cu concentration of the matte. In high-SiO2 concentrationslags, excessive MgO in the liquid slag recrystallized as solid olivine (Mg2SiO4−Fe2SiO4), increasing the slag viscosity and copper losses in the slag. The maximum MgO solubility in the FeOx−SiO2−MgO slag increased from 3 wt.% to 8 wt.% when the temperature raised from 1200 to 1300 °C under p(O2) of 10−6 kPa. At higher MgO content, the slag composition could be optimized by increasing temperature and adding SiO2 flux to maintain a fully molten slag or avoid high proportions of solids.

Thermodynamic evaluation of viscosity behavior for CaO–SiO2–Al2O3–MgO slag systems examined at the temperatures range from 1500 to 1700 °C

This work showed an application of computational tools to understand systematically the behavior of viscosity on CSAM systems relevant to industrial uses. Consequently in this study, the viscosity experimental data obtained from the literature were compared with the thermodynamic calculated results via the software FactSage v.7.3 for melts in CaO–SiO2–Al2O3–MgO slag system with the range of compositions slags cover 0–100 wt% CaO, 0–100 wt% SiO2, 0–100 wt% Al2O3 and 0–15 wt% MgO at temperature ranges of 1500–1700 °C. Using open-source software in Python, the results of viscosity, liquid, and solid fraction of the slag, as a function of composition and temperature, are represented by multiple color maps and by iso-viscosity contours. The results of the viscosity values indicated that the effect of all the oxides in the CSAM slag system follows the well-known behavior trend observed in the literature. Viscosities of the slag were found to increase with increasing SiO2 contents and decrease with increasing basicities (high CaO). The increase in Al2O3 content increases the viscosity values. An increase of 0–15% MgO depolymerized the slag melt and decreases the viscosity. However, above 5% MgO content occur a decrease in the liquid zone (single phase) and a liquid fraction (two-phase region) of the slag. For a constant MgO concentration, the increase in temperature generates an expansion of low-viscosity zones associated with an increase in the liquid phase of the slag. From the comparison between the calculated and experimental viscosities data keeps up within 30% average relative deviation (Δ), the predictions are considered acceptable for viscosity in the CSAM slag system at high temperatures.

Study on the influence of different contents of impure CaO on the process of electromelting magnesia

PurposeThe aim of this study is to report the effect of different content of calcium oxide on the process of electromelting magnesia.Design/methodology/approachThe process of molten magnesia was analyzed by finite element simulation and proved by scanning electron microscope.FindingsThe results show that with the increase of CaO content, the maximum temperature appreciation increases from 3,616°C To 3,729°C, showing an approximate nonlinear evolution. Low thermal conductivity and low specific heat of CaO result in higher temperature. With the increase of CaO content and temperature, the maximum flow velocity of MgO slag increases from 0.043 to 1.34 mm/s. Under different initial CaO contents, the distribution trend of CaO volume fraction is basically the same, and the CaO volume fraction is evenly distributed between 50 and 225 mm in the furnace.Originality/valueThe influence of different contents of impurity calcium oxide on the process of electromelting magnesia was analyzed and a theoretical system was established.

Effect of MgO on wetting and corrosion behaviour of corundum substrate by CaO–SiO2–MgO (–Al2O3) slags

ABSTRACT Effect of MgO content on wetting and corrosion behaviour of corundum substrate by CaO–SiO2–MgO (−15%Al2O3) molten slags was investigated at 1450°C via joint application of a sessile drop technique, SEM–EDS detection and FactSage thermodynamic software. All slags exhibit good wettability on the substrate, and the contact angle values are small. Increasing MgO content from 7% to 9% in CaO-SiO2-MgO slags can increase the contact angle between the droplet and the substrate, while the substrate dissolution thickness and the slag penetration depth tend to decrease. Increasing MgO content from 8% to 15% in CaO-SiO2-MgO-15% Al2O3 slags can also increase the contact angle, but significantly decrease the slag penetration depth. The indirect dissolution thickness increases instead due to the formation of a large amount of MgAl2O4 by the interface reaction. The wettability can give an indication of the slag penetration depth in the substrate but not the dissolution thickness of the substrate.

Influence of Slag Chemistry on the Dissolution of FeCr<sub>2</sub>O<sub>4</sub> in CaO–SiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO Slag with Graphite Crucible

The effect of Al2O3 and SiO2 content and basicity (w(CaO) + w(MgO)/w(SiO2) + w(Al2O3)) on the chromite ore dissolution in CaO–SiO2–Al2O3–MgO slag system was studied under the condition of 1550°C. The results show that the increase of basicity (R = 0.54, 0.67, 0.82) results in the reduction of the dissolved amount and dissolution rate of chromite ore in the slag. The dissolved amount of Cr in lower basicity slag (R = 0.54) is about 1.5 to 2 times higher than that in higher basicity slag (R = 0.67, R = 0.82). The dissolved amount of Cr tends to increase when the Al2O3 mass content decreases from 20% to 15%. While as the Al2O3 mass fraction continues to decrease from 15% to 10%, the dissolved amount begins to decrease. This may be related to the viscosity of the slag. The spinel phase tends to form on the surface of the unreacted FeCr2O4, thus hindering the further dissolution of FeCr2O4. After starting to dissolve, the FeCr2O4 decomposes into FeO and Cr2O3 dissolving in the slag. The FeO in the slag is preferentially reduced to metal iron attached to the surface of the FeCr2O4. The main forms of Cr element in the slag are CrO and Cr2O3, and the proportion of these two depends on the composition of the slag and the experimental environment. The proportion of CrO in the slag with lower basicity is larger. In the experiment, the maximum solubility of FeCr2O4 in 60 min was obtained in the slag system with 45% SiO2, 15% CaO, 20% Al2O3 and 20% MgO.

Combining experimental analyses and molecular dynamics simulations in impurity removal at the Si/slag interface

Slag refining is a crucial step for Si purification by the metallurgical processes. In this study, the impurity removal at Si/SiO2–CaO–MgO slag interface was investigated experimentally and theoretically. The diffusion couple experiments show that the slag underwent the processes of sintering, solid particle dissolution, and composition homogenization. When the melted slag contacted the Si, the interfacial reaction occurred, and the impurity oxides formed and transferred into the slag phase. The thermodynamic analyses confirmed the existence of the oxidation reaction between impurities and slag. First-principles molecular dynamics simulations of the Si–X–O system (X = Al, B, Ca) clarified the binding behaviors of Al, B, Ca with Si. The calculated binding energy shows that the affinity ability of these impurities with Si are B > Al > Ca at the molecular level, and B impurity is the most difficult one to be removed from Si during the slag refining process.

Slag refining at various viscosity conditions for SiC inclusion removal during Si scraps recycling

SiC inclusions in cast Si ingots are a key problem for Si quality and in the recycling of top-cut Si scraps. In this paper, SiC separation and Si recovery in the CaO–SiO2–MgO slag refining process were studied by varying temperature, slag/Si–SiC mass ratio, slag composition, and holding time. When the viscosity of the mixed system viscosity was 0.1575 Pa s, it was the best condition for the migration of SiC inclusions from Si to slag, and the removal ratio of SiC is 91.6%. The results indicated that low-viscosity slag and a long holding time are conducive to the migration of SiC. Further Image Pro software analysis showed that increasing the MgO content to 30mol% is beneficial to promote the migration of SiC. It is also found that the system viscosity effected the size of SiC in the slag phase. This work improves the removal of key inclusion SiC, reducing the cost of Si recovery.

Analysis of the use of magnesium-containing additives in the charge of iron flux in order to reduce CO2 emissions

The growing requirements for the quality of finished steel products oblige to obtain steel with a low content of harmful impurities, especially sulfur. The main charge for steel production in the conditions of JSC EVRAZ NTMK is vanadium iron, the external desulfurization of which leads to large losses of valuable vanadium. Therefore, the smelting of iron with a low sulfur content is an urgent task. The main way to reduce sulfur in iron is to increase the basicity of the slag (B2), but MgO is the best desulfurizer. The paper evaluates the effectiveness of the use of various magnesium-containing materials in the conditions of the blast-furnace stage of JSC EVRAZ NTMK, taking into account CO2 emissions. The possibility of replacing limestone in the iron flux charge with dolomite, as well as with steel converter slag, is considered. Both materials will increase the proportion of MgO in blast-furnace slag, however, the use of dolomite is accompanied by a two-fold increase in CO2 emissions compared to limestone. Converter steel slag (CSS) does not contain carbonates, thus eliminating the formation of CO2 during the limestone decomposition. An additional advantage of CSS is its high content of valuable vanadium and manganese. The effect of an increase in MgO in slag on its melting point is considered. It has been established that an increase in the proportion of MgO to 14% will not cause difficulties in the processing of blast-furnace smelting products and will reduce the sulfur content in iron and the formation of titanium carbides and carbonitrides.

Radical reaction-induced Turing pattern corrosion of alumina refractory ceramics with CaO–Al2O3–SiO2–MgO slags

Quasi-volcanic corrosion occurs at the triple-phase interface of alumina refractory ceramics and MgO-containing CaO–Al2O3–SiO2 slags in the air, causing severe damage to ceramics. To address this limitation, in this study, a slag corrosion experiment is performed on alumina refractory ceramics using CaO–Al2O3–SiO2–MgO slags. Various spectroscopic techniques, including electron paramagnetic resonance spectroscopy, are used to investigate the influence of slag structures with varied MgO contents on the corrosion peaks and mechanism. The results show large quantities of reactive radicals, including superoxide radicals, in the slags. Free-radical reactions between refractory ceramics and slags lead to Turing pattern corrosion. An increase in the amount of non-bridged oxygen in the slag structure decreases the amount of original superoxide radicals. Consequently, the intensity of the free-radical reactions of alumina dissolution increases, thereby increasing the height of the corrosion peaks.

Dissolution mechanism of alumina inclusions into CaO–SiO 2 –Al 2 O 3 –Fe t O–MgO slag via a converter tapping process

Reducing the amount of inclusions during the steelmaking process as much as possible and much earlier plays a vital role in improving the quality of steel products. To reveal the dissolution mechanism of inclusions in slag during the converter tapping process, some comparison experiments were conducted by adding isolated spherical alumina balls as inclusions in CaO–SiO2–Al2O3–FetO–MgO slag, and FetO content up to 10% was contained in slag. The results showed that the dissolution rate of alumina balls in the slag was mainly affected by the diffusion of Al2O3, and the diffusion coefficients of Al2O3 were 4.2 × 10–11, 7.5 × 10–11, and 1.5 × 10–10 m2/s at 1500℃, 1550℃, and 1600℃, respectively. In addition, the upgraded diffusion-distance-controlled dissolution model (DDD-Model), in which FetO content was introduced and applied in the study. The results illustrated that the Al2O3 inclusion apparent dissolution rate was improved by a high FetO content, increasing CaO/SiO2 and raising the temperature as soon as possible at the early stage of the converter tapping process. It is not necessary to increase the FetO content in the slag to enhance the dissolution rate of the Al2O3 inclusion at the last tapping stage. The predicted complete dissolution time of spherical Al2O3 inclusions with 1000 µm in diameter based on the upgraded DDD-Model was approximately 1796 s during the actual converter tapping process.