Low Carbon MgO Research Articles

Stress–strain behaviour and degradation mechanism of low–carbon MgO–C refractories at 900–1100 °C: role of TiB2–BN–AlN waste

The use of boron–containing additives often raises concerns when exposed to high temperatures. In this study, the high temperature stress–strain behavior and degradation mechanism of low–carbon MgO–C refractories containing TiB2–BN–AlN waste were investigated. Stress–strain curve, peak axial stress, Young’s modulus, cohesion, and residual strength ratio after thermal shock tests were thoroughly analyzed. The findings suggest that the mechanical properties of refractories remain unimpaired within the temperature range of 900–1100 ℃, and can even be enhanced through the synergistic effect of TiB2–BN–AlN waste and Al powder. The optimized axial stress increased from 55.0 to 62.0 MPa at 1100 ℃, while the cohesion increased from 10.0 to 13.8 MPa, respectively. The observed enhancement can be primarily attributed to the effective healing of pores and cracks, reduction in oxidation, and improved material cohesion. However, the excessive incorporation of boron–containing waste may compromise the performance of refractories, leading to instability or degradation.

High temperature mechanical properties of novel MgO–Al3BC3 refractories for electric arc furnace lining

In this study, novel MgO–Al3BC3 refractories were developed by gradually replacing flake graphite with Al3BC3 in unfired low–carbon MgO–C refractories. The high temperature mechanical properties of these novel refractories were investigated for the first time. The results demonstrated significant enhancements in cold crushing strength, thermal shock resistance, and hot modulus of rupture when compared with low–carbon MgO–C refractories. These enhancements can be attributed to the formation of an appropriate amount of boron–containing liquid phases within the novel MgO–Al3BC3 refractories at elevated temperatures. These liquid phases serve multiple functions, including acting as a mineralizer for MgAl2O4, facilitating self–healing by filling cracks and pores, and strengthening the bonding between the aggregate and matrix interface. Furthermore, the thermal stability of Al3BC3 enables it to maintain its functionality consistently, even at high temperatures.

Effect of micro-Al2O3 powders on oxidation and corrosion behaviors of low-carbon MgO–C refractories

Effect of micro-Al2O3 powders on oxidation and corrosion behaviors of low-carbon MgO–C refractories

Oxidation behavior of low–carbon MgO–C refractories under thermal cycling: The potential of TiB2–BN–AlN industrial waste

MgO–C refractories are employed as linings for high–temperature containers where they are susceptible to thermal shock and oxidation. In this work, the oxidation behavior of low–carbon MgO–C refractories under thermal cycling was investigated for the first time, and the potential utilization of TiB2–BN–AlN (TBA) industrial waste as an additive was also investigated. The results showed that the traditional antioxidant Al was basically ineffective under the condition of thermal cycling; however, the incorporation of TBA industrial waste effectively maintains exceptional oxidation resistance, regardless of thermal cycling. This can be attributed to its capacity to seal the porosity, prevent oxygen intrusion, and absorb elastic strain energy while reducing stress. Additionally, when exposed to an oxidizing atmosphere, MgO–C refractories containing only TBA industrial waste exhibit a low thermal expansion coefficient.

Enhanced mechanical performance of in–situ Mg–sialon in low–carbon MgO–C refractories through Si–Al4SiC4 additions

In this study, a novel MgO–C refractory, fabricated through high–temperature nitriding, was developed by incorporating Si–Al4SiC4 to in–situ form plate–like Mg–sialon ceramic bonding phase in situ. The influences of Al4SiC4 content and nitriding temperature on the phase transformation, microstructure, and mechanical properties of MgO–C refractories were examined. The synergistic effect of Si co–existed with Al4SiC4 promoted the in–situ formation of plate–like Mg–sialon, thereby accelerating the densification of MgO–C refractories. The primary crystal growth surface for Mg–sialon was identified as the (100) facet. The plate–like Mg–sialon was integrally bonded within the matrix, enhancing the interfacial bonding with MgO particles, rather than merely adhering to the surface. The incorporation of 2 wt% Al4SiC4 significantly optimized the microstructure of MgO–C refractories, culminating in superior mechanical properties when nitrided at 1400 °C. Furthermore, the formation mechanism and morphological evolution of the plate–like Mg–sialon in MgO–C refractories were explored.

Corrosion mechanism of novel MgO–Al3BC3 refractories in contact with converter slag

The corrosion mechanism of novel MgO–Al3BC3 refractories in contact with converter slag was investigated. Results demonstrated that refractories with an optimized Al3BC3–Al composition exhibited significantly reduced corrosion index compared with low–carbon MgO–C refractories. The superior corrosion resistance was primarily attributed to the formation of a dense protective layer composed of MgO–MgAl2O4–Mg3B2O6, which was achieved at 1100 °C by combining Al3BC3–Al. These protective layers with enhanced diffusion barriers effectively impedes the penetration and solid solution of Ca and Fe ions, thereby also optimizing the slag viscosity. The self–healing capability of the novel MgO–Al3BC3 refractories further enhances their corrosion resistance.

A novel route to enhance high-temperature mechanical property and thermal shock resistance of low-carbon MgO–C bricks by introducing ZrSiO4

A novel route to enhance high-temperature mechanical property and thermal shock resistance of low-carbon MgO–C bricks by introducing ZrSiO4

Effect of C/MgO nanocomposite powders on the properties of low-carbon MgO–C refractories

To produce high performance low carbon MgO–C refractories, the combustion synthesized MgO nanofibers containing C/MgO composite powders (SCM) were introduced. The effect of SCM on the mechanical properties, thermal shock resistance, oxidation resistance and slag resistance of MgO–C refractories has been studied, along with exploring the toughening mechanism on thermal shock resistance. The results showed that the refractories containing 6 wt% SCM (M6) exhibited the most favorable comprehensive properties. Compared to reference sample M0, M6 showed significant enhancements in thermal shock resistance, oxidation resistance, and slag resistance by 38.6%, 29.8%, and 23.9%, respectively. Notably, the unique microstructure of MgO nanofibers and carbon encapsulated MgO played a crucial role in facilitating crack deflection and branching, which promote the generation of microcracks and the consumption of strain energy. These mechanisms contributed to the improvement in thermal shock resistance of refractories.

Improved thermal shock stability and oxidation resistance of low-carbon MgO–C refractories with introduction of SiC whiskers

This research focuses on the utilization of SiC whiskers synthesized from rice husk powders in low-carbon magnesia–carbon (MgO–C) refractories, and attempts to reduce the flake graphite content in refractories by adding synthesized SiC whiskers. The effect of the addition amount of SiC whiskers on the microstructure, mechanical properties, thermal shock stability and oxidation resistance of MgO–C refractories with different graphite content was studied. The results indicated that the introduction of SiC whiskers facilitated the generation and growth of ceramic phases in MgO–C refractories. By adding 1 wt% SiC whiskers, the graphite content could be reasonably reduced (from 5 wt% to 4 wt%), and the strength, thermal shock stability and oxidation resistance of refractories were enhanced by the synergistic effect of the introduced SiC whiskers and the generated ceramic phases, the CMOR, CCS, residual CCS, and oxidation resistance were increased by 44, 6, 12 and 27% respectively.

Application of SiC whiskers synthesized from waste rice husk in low-carbon MgO–C refractories

In this study, we converted renewable rice husk into SiC whiskers and added them to low-carbon MgO–C refractories to investigate their effect on the structure, thermomechanical properties, and slag resistance of the refractories. Overall, the addition of 1 wt% SiC whiskers promoted the growth of columnar β-Si3N4 and flaky Mg2SiO4, and the refractories maintained high mechanical properties after thermal shock as compared to the refractories without addition of SiC whiskers. In particular, the CMOR and CCS before and after thermal shock were increased by 32%, 16%, 17%, and 19%, respectively. Further, the SiC whiskers loaded with catalyst (denoted as SiCwsc, 1 wt%) were introduced into refractories, the presence of the catalyst resulted in a change in the whisker structure to a chain-bead morphology, which improved the bonding strength with the matrix. Moreover, the introduced catalyst also promoted the formation of columnar β-Si3N4 and flaky Mg2SiO4. The mechanical properties, thermal shock resistance, and slag resistance of the refractories were further enhanced, its CMOR and CCS before and after thermal shock were 11.0 MPa, 9.3 MPa, 68.8 MPa, and 56.0 MPa, respectively.

Elucidating the role of Ti3AlC2 and Ti3SiC2 in oxidation mechanisms of MgO–C refractories

Two types of Ti-containing layered ternary carbides, Ti3AlC2 and Ti3SiC2, were incorporated to fabricate low-carbon MgO–C refractories, and the oxidation behaviors after exposure to 1100 °C and 1500 °C were investigated in the present work. The oxidation resistances of the samples with Ti3AlC2/Ti3SiC2-adding have an approximately 50% increase over that of conventional MgO–C with 4 wt% graphite. CT results indicated stress cracks occurred in the sample with Ti3AlC2/Ti3SiC2-adding after exposure to 1100 °C, it was attributed to the anomalous oxidation behavior of Ti3AlC2/Ti3SiC2 grains and the formation of TiO2 with volume expansion at ∼600 °C according to TG and corresponding XRD results. At 1500 °C, a white reaction product layer was formed at the boundaries of oxide/non-oxide layers of the sample with Ti3AlC2/Ti3SiC2-adding, which was confirmed as magnesium titanate spinel. The oxidation behaviors of the samples with Ti3AlC2/Ti3SiC2-adding showed a mass gain process owning to the further disintegration of Ti3AlC2/Ti3SiC2. Furthermore, the oxidation mechanism and the roles of Ti3AlC2/Ti3SiC2 grains were elucidated in detail.

Enhanced oxidation resistance of low-carbon MgO–C refractories with ternary carbides: a review

Enhanced oxidation resistance of low-carbon MgO–C refractories with ternary carbides: a review

Designing low-carbon MgO–Al2O3–La2O3–C refractories with balanced performance for ladle furnaces

In order to achieve high-quality and stable production of special steel, the performance of low-carbon MgO-C refractories needs to be further optimized. For this purpose, low-carbon MgO–Al2O3–La2O3–C refractories with enhanced thermal shock resistance and slag resistance were designed and successfully prepared by introducing Al2O3 as a reinforcer and La2O3 as a modifier. The results showed that the refractory samples with additives show better overall performance than those without additives. When 10 wt% of Al2O3 and La2O3 were added, the oxidation resistance, thermal shock resistance and slag resistance of the refractory samples coked at 1400 °C are increased by 13.57%, 17.75% and 43.09%, respectively. The analysis found that this can be mainly attributed to the formation of MgAl2O4, Mg2SiO4, and 2CaO·4La2O3·6SiO2 and the consequent volume expansion effect and intergranular phase enhancement effect. Therefore, a low-cost and enforceable reinforcement strategy for low-carbon MgO-C refractories is proposed, which is expected to be applied in steelmaking.

Application of Cr3C2/C composite powders synthesized via molten-salt method in low-carbon MgO–C refractories

High-performance and low-carbon MgO–C refractories are important refractories for smelting ultra-low carbon steel and clean steel. Based on this, Cr3C2/C composite powders were synthesized by the molten-salt method, and used as an additive to prepare low-carbon MgO–C refractories under nitrogen atmosphere. The phase, morphology and oxidation kinetics of Cr3C2/C composite powders were studied. In addition, the effect of Cr3C2/C composite powders on the morphology, mechanical properties, thermal shock resistance, and corrosion resistance of MgO–C refractories was investigated. The results indicated that the Cr3C2/C composite powders exhibited superior oxidation resistance than flake graphite. Moreover, the Cr3C2/C composite powders were introduced into the MgO–C refractories. Compared with the sample without Cr3C2/C composite powders, the introduction of 1 wt% Cr3C2/C composite powders significantly improved the thermomechanical properties and corrosion resistance of the material, its CMOR, CCS before and CCS after thermal shock were 9.06 MPa, 50.40 MPa and 32.60 MPa, respectively, and the corrosion index was significantly reduced from 44.6% to 26.5%.

Catalytic preparation of carbon nanotube/SiC whisker bonded low carbon MgO–C refractories and their high-temperature mechanical properties

The effects of Co, Fe and Ni catalysts generated from their nitrate precursors on the formation of carbon nanotubes (CNTs) from pyrolysis of phenolic resin were investigated, and the former two performed the best at 873 K, and 1073–1273 K, respectively. Density functional theory calculations indicate that a Co nanocluster requires the lowest energy for forming the five-membered carbon ring (the controlling step in the CNT generation), making Co the best catalyst for the formation of CNTs at relatively low temperatures. On the other hand, molecular dynamics calculations show that an Fe nanocluster has the highest melting point among the three nanoclusters and can retain its integrity at 1280 K, making Fe the best catalyst for the formation of CNTs at relatively high temperatures. Hot modulus of rupture of the CNT (along with additionally formed SiC whisker) reinforced low-carbon MgO–C refractory sample containing 0.25 wt% Fe catalyst was about 20% higher than that of its catalyst-free counterpart.

Comparative study of B4C, Mg2B2O5, and ZrB2 powder additions on the mechanical properties, oxidation, and slag corrosion resistance of MgO–C refractories

Boron-containing additives are used to improve the oxidation resistance of carbon-containing refractories; however, their effects on the mechanical properties and slag corrosion resistance of the refractories have rarely been studied. In this work, B4C, Mg2B2O5, and ZrB2 powders were incorporated into low-carbon MgO–C refractories to study their effects on the mechanical properties, oxidation resistance, and slag corrosion resistance of the refractories. The relationships between these properties and the microstructure and phase evolution were also studied. The results show that the flexural strengths of the MgO–C refractories at high temperatures are closely related to the apparent porosity and formation of an Mg3B2O6 phase. The oxidation resistances are greatly improved after the introduction of boron-containing additives into the MgO–C refractories in terms of both thermodynamical aspects and the filling of voids and pores. The most effective antioxidant is B4C, followed by the ZrB2 and Mg2B2O5 powders. The mechanisms through which the vanadium-containing slag attacks the MgO–C refractories mainly include the dissolution of magnesia to form melting phases, penetration through pores, and redox reaction with carbon.

Potential Application of Sic Whisker Synthesized from Biomass Waste-Rice Husk in Low-Carbon Mgo–C Refractories and Their Property Optimization

Potential Application of Sic Whisker Synthesized from Biomass Waste-Rice Husk in Low-Carbon Mgo–C Refractories and Their Property Optimization

Influence of pre-synthesized Al2O3–SiC composite powder from clay on properties of low-carbon MgO–C refractories

Influence of pre-synthesized Al2O3–SiC composite powder from clay on properties of low-carbon MgO–C refractories

Molten salt synthesis of Cr3C2-coated flake graphite and its effect on the physical properties of low-carbon MgO–C refractories

To improve the performance of low-carbon MgO–C refractories, the Cr3C2-coated flake graphite was synthesized by molten salt method, then the Cr3C2-coated flake graphite was added to low-carbon MgO–C refractories. In this work, the effects of reaction temperature, Cr/C mole ratio, and holding time on the synthesis of Cr3C2-coated flake graphite were studied. Furthermore, the effect of Cr3C2-coated flake graphite on the physical properties of low-carbon MgO–C refractories was evaluated. The results indicated that when the reaction temperature was 950 °C, Cr/C molar ratio was 1/2 and holding time was 3 h, the synthesized Cr3C2-coated flake graphite had fewer surface micropores and the crystallinity of Cr3C2 grains was high. In addition, the Cr3C2-coated flake graphite exhibited excellent oxidation resistance. MgO–C refractories containing 2 wt% Cr3C2-coated flake graphite exhibited more excellent physical properties. The results of nano CT detection system showed that the addition of Cr3C2-coated flake graphite promoted the densification of MgO–C refractories.

Enhanced performance of low-carbon MgO–C refractories with nano-sized ZrO2–Al2O3 composite powder

Low-carbon MgO–C refractories are facing great challenges with severe thermal shock and slag corrosion in service. Here, a new approach, based on the incorporation of nano-sized ZrO2–Al2O3 composite powder, is proposed to enhance the thermal shock resistance and slag resistance of such refractories in this work. The results showed that addition of ZrO2–Al2O3 composite powder was helpful for improving their comprehensive performances. Particularly, the thermal shock resistance of the specimen containing 0.5 wt% composite powder was enhanced significantly which was related to the transformation toughening of zirconia and in-situ formation of more spinel phases in the matrix; also, the slag resistance of the corresponding specimen was significantly improved, which was attributed to the optimization of pore structure and formation of much thicker MgO dense layer.