Ladle Slag Research Articles

Stabilisation of estuarine sediments with an alkali-activated cement for deep soil mixing applications

In this work, an alternative alkali-activated cement (AAC) made of ladle slag precursor mixed with sodium hydroxide and sodium silicate has been developed to enhance the bearing capacity of estuarine soils in coastal conditions via deep soil mixing (DSM). The AAC was optimized to use a low reactivity precursor (ladle slag) and to deal with a contaminated high-water content natural sediment cured under water. The material performance was analysed by comparison to a mixture made with Portland cement and cured in the same conditions. Flexural and unconfined compressive strength tests as well as seismic waves measurements after 3-, 7-, 14- and 28-d curing were performed to obtain a relationship between elastic stiffness and strength with curing time for both mixtures. Remarkably, the AAC mix demonstrated superior strength results, exhibiting almost double flexural and compressive strengths after 28 d compared to the Portland cement mix. The AAC mix also showed a higher rate of stiffness increase than the Portland cement mix, which has a higher initial stiffness at young ages but lower stiffness evolution. Leachate analysis confirmed that the proposed AAC could effectively immobilise any contaminants from soil or precursors. The effect of curing under stress was analysed in triaxial compression tests and found to be insignificant, indicating that laboratory data obtained without stress curing can represent the material's behaviour in a DSM column, which will cure under the weight of the column.

Ladle Furnace Slag: Synthesis, Properties, and Applications

AbstractLadle slag is a byproduct formed during the ladle refining stage of steel making. It is a dusty material that has been considered industrial waste. Technical advancements towards a sustainable industry led to the development of different applications for ladle slag. Depending on the processing methods during the steel slag production and the weathering of the slag post‐production, the elemental composition of the steel slag largely varies. Owing to this, its characteristics cannot be generalized and specific applications depending on the sources are developed. It is generally used in construction materials, soil rejuvenation, and CO2 capture. This paper reviews the production process, the mineralogical and morphological properties, stabilization techniques, and the applications of ladle furnace (LF) slag. One of the prime focuses of waste remediation and sustainable industry is to find meaningful ways to turn waste into products. In this respect, a comprehensive review of the properties of LF slag and its current application will help provide a framework for the development of future sustainability goals. With increased slag usage, the ladle refining process of steelmaking can be turned into a more carbon‐neutral process.

The Incorporation of Ladle Furnace Slag in Fire Insulating Gypsum-Based Materials

Ladle slag, a byproduct of steel manufacturing, exhibits inherent reactivity and undergoes hydration when exposed to water. Nevertheless, these reaction byproducts often remain metastable, leading to microstructural alterations when incorporated into cementitious materials, thereby limiting the recycling potential of ladle slag. This study explores the fire insulating capacity and the physical, mechanical, and leaching characteristics of gypsum-based materials with substantial quantities of ladle slag in instead of gypsum. The mechanical strength of the specimens declines as the ladle slag content increases. Nevertheless, the percentage decrease in compressive strength at various temperatures (300 °C, 500 °C, and 700 °C) is less pronounced when higher amounts of ladle slag are used. Fire-resistant properties, assessed using the EN 1363-1 standards, diminish with increasing slag proportions; although the inclusion of ladle slag introduces certain endothermic processes that positively affect the fire insulating capacity, resulting in a 20% reduction when 60%wt of slag is employed. Notably, no gas emissions were observed during the fire test, indicating the absence of environmental hazards. In conclusion, ladle slag does not pose a leaching threat to the environment, making it a viable and sustainable alternative to gypsum in gypsum-based materials.

Effect of MgO on Evolution of Interface Structure between Low‐Basicity Refining Slag and MgO–C Refractory

MgO–C bricks are widely used as a refractory lining in the slag line part of the ladle of a cord steel refining. The dissolution of their main component MgO into the refining slag is one of the main reasons for their shortened service durability. Laboratory experiments are carried out using low‐alkalinity refining slag and unaltered MgO–C bricks by static crucible method. Physicochemical analysis, FactSage thermodynamic calculations, etc., are performed on the specimens, and the dissolution mechanism of magnesia is investigated. When the low‐melting‐point‐phase CaMgSiO4 (CMS) decomposes at high temperatures, the concentration and activity of (MgO) at the local interface between slag and MgO‐C brick increase rapidly, inhibiting the dissolution of magnesia into slag at the CMS in situ. The rapid weakening of the dissolution drive of the slag to the magnesia corrosion occurs when the MgO content in the refining slag approaches saturation. To verify the feasibility of extending the service life of MgO–C bricks at the refining ladle slag line, the study involves controlling the MgO content in the refining slag.

Use of ladle slag for CO2 sequestration and zinc immobilization

Environmental pollution, waste management, and greenhouse gas emissions pose significant challenges to global sustainable development. To address these challenges, this study introduces an innovative approach by reusing an industrial waste, ladle slag (LS), and greenhouse gas, CO2, for fast immobilization of zinc. In this study, specimens were prepared by mixing LS with zinc nitrate with initial concentrations of 0–25,000 mg/kg and then subjected to conventional and CO2 curing. Leaching test and chemical analysis tests were also conducted. The results showed that LS with CO2 requires only 112 hours to achieve around 2–3 times lower leaching concentrations than that of conventional curing for 28 days, being around 1–2 orders of magnitude lower than that without CO2 and conventional curing. Simultaneously, CO2 up to 13.5 % of LS mass was also sequestered. This approach provides a triple benefit by simultaneously immobilizing zinc, mitigating LS landfilling, and capturing CO2.

EPA LEAF Testing of a Powdered Ladle Slag to Support pH Neutralization and Stabilization/Solidification Applications

EPA LEAF Testing of a Powdered Ladle Slag to Support pH Neutralization and Stabilization/Solidification Applications

Chemical Range of Stability for Self-Dusting Ladle Furnace Slags and Destabilizing Effect of Sulfur

Ladle furnace slags are characterized by volumetric expansions associated with the transition of dicalcium silicate (C2S) from β to γ phase, which generates fine dust during cooling, causing handling and storage issues that further reduce their recycling opportunities. The present work focuses on the effect of slag basicity on dusting and the role of sulfur on slag stability. Seven synthetic ladle slag precursors were made by mixing lime, magnesia, quartz and alumina in different proportions to match effective industrial compositions, increasing the binary basicity and keeping the ternary and quaternary indexes unchanged. Samples were heated to 1500 °C for 15 min and monitored during air cooling (< 5 °C/s) through thermocouples and camera to characterize the behavior, temperature, and time interval of dusting. The cooled samples were characterized chemically, mineralogically and morphologically. Starting from the chemistry of a self-stabilized slag, five additional slag precursors, characterized by increasing amounts of S, were created and analyzed using the same procedures. Experimental evidence showed the presence of three different dusting behaviors (stable, partial and complete) and stabilization of the slag once an optical basicity of 0.748 or higher was reached. In addition, mayenite was identified as the main phase capable of suppressing the β to γ transition by exerting hydrostatic pressure on C2S. Finally, although S can stabilize the β phase when dissolved in it, after saturation it precipitates as CaS, which can react with mayenite, locally decreasing the optical basicity and allowing dusting.Graphical

Experimental investigation on strength, durability and micro structural characteristics of slag based concrete

In this study, experimental investigations are conducted using 100 percent Portland Slag Cement and Processed Granulated Blast Furnace Slag sand (PGBFS, iron slag) with 100 percent and partial or full replacement of Natural Coarse Aggregates (NCA) with Ladle Slag Aggregates (LSA) with 0, 20, 40, 60, 80, and 100 percent variations. All of the materials used in the inquiry are manufactured by Jindal Steel Works' Bellary factory in India. It has been shown that aggregates containing 20 percent Ladle slag provide the highest strength. Again, 5 percent variation strength tests are conducted, and it is determined that maximum strength is attained with 20 percent variance. The XRD examination demonstrates that the intermolecular bonding between hardened aggregate and cementitious paste is mostly comprised of silicates with a high degree of crystalline order. Due to the fact that the XRD test pattern is mostly composed of quartz aligned with alite and belite, the spaces between the substrate have been minimized to a minimal extent, which may contribute to the concrete's excellent endurance. For 20 percent variance, the tests of durability are modest, as shown by the durability test. The SEM images show porous structures which suggest a limited formation of C-S-H, gel and a correlation between them. The calcium hydroxide generated during cement hydration could be the result of interaction with the reactive amorphous silica present in slag and cement, leading to the formation of C-S-H gel, which plays a role in enhancing the mechanical and durability properties of concrete.

Application of refractory materials for steel ladles

The article analyzes the service life of refractories and various options for combined lining of steel ladles used in steelmaking shops with out-of-furnace steel processing departments, and identifies the main trends in its development. The use of various types of lining is analyzed based on the experience of Japan, Germany, Austria, and France. The technological conditions of operation of steel ladles with the main lining are considered. Under operating conditions, the lining areas near the slag belt and the place where the jet hits the bottom of the ladle are subject to the greatest destruction, so it is advisable to install high-quality refractories in these areas. In addition, the reasons for the insufficient stability of refractories are identified, including decarburization, corrosion, ladle slag formed during out-of-furnace metal processing, the use of synthetic additives to slag, high thermal conductivity of refractory materials during operation, and others. Ways to increase the service life of steel ladles are identified. It is shown that the world practice is characterized by the use and intensive improvement of the main lining of steel ladles through the use of new materials with increased refractory and operational characteristics. The experience of refractory improvement by Shinagawa Refractories, TYK Corp, Plibrico, Nippon Steel, Krosaki Harima, and IPSCO Steel, including practical testing at production, is presented. It is established that the high cost of consumables and increased requirements for manufacturing technology hinder the massive introduction of the developed technologies at metallurgical enterprises

Treatment of cadmium-contaminated soil using ladle slag with and without CO2

Cement and lime are widely used to stabilize/solidify (S/S) contaminated soils, however, the production of ordinary Portland cement (OPC) and lime causes CO2 emission and consumption of energy and non-renewable resource. In this context, this study proposes a sustainable S/S approach by utilizing an industrial by-product, ladle slag (LS), and carbon dioxide (CO2), to substitute cement and lime for treating cadmium (Cd)-contaminated soil. In laboratory investigation, contaminated soils spiked by Cd with concentrations of 0–32,000 mg/kg were treated by LS with a binder content of 10 % and subjected to conventional curing and carbonation curing for different periods varying from 3 hours to 112 days. The results showed that LS with conventional curing could reduce the leaching of Cd, however, it was still less effective than OPC in S/S of Cd-contaminated soils under the same curing period of 28 days. When CO2 was introduced, LS with CO2 rapidly decreased the leaching of Cd in soils by five orders of magnitude, using only 104 hours to achieve better S/S efficacy than OPC with conventional curing for 28 days. The LS with carbonation curing also sequestered CO2 up to 16 % of LS mass and yielded higher strength than that without CO2.

Optimal Control of Inclusions to Prevent “Sand-Hole” Surface Defects in Deep Cold-Drawn Battery Cups for Electrical Vehicles

The present work was conducted to elucidate the influence of inclusionson surface quality of deep cold-drawn battery cups for electrical cars. The obtained results revealed that, to prevent the surface defects of sand-holes in battery cups in deep cold-drawing process, attentions should be paid to steelmaking and casting process for optimal control of inclusions. Because sand-holes were often caused by large Al2O3 clusters and CaO-Al2O3 particles. Most important, a worthy finding was that these inclusions were not safe when they were over 100 μm and bigger than 27 μm, respectively, which was important for process optimization. By reducing (FeO) contents in ladle slag and tundish covering flux to about 5% or lower, together with optimal fluid flow of molten steel in tundish, such large inclusions can be well decreased to prevent the occurrences of sand-holes in battery cups in industrial production.

Evaluation of low-cost oxygen carriers for biomass chemical looping gasification

Biomass Chemical Looping Gasification (BCLG) is a cost-effective and efficient alternative to conventional gasification. The selection of appropriate oxygen carriers (OCs) is crucial for stable BCLG performance. These OCs need to possess high reactivity, selectivity, material strength, and resistance to sintering. The study investigated various OC materials, including industrial wastes (copper, nickel slag, desulphurization, LD, and ladle slags), residential waste (sewage sludge ash), and natural ore (manganese). The evaluation of OCs focused on reactivity, H2-selectivity, mechanical strength and sintering behaviour. Except for ladle slag, all OC samples exhibited favourable reactivity due to the presence of Fe- and Mn-oxides possessing high oxygen transport capacity (10–17.6%). Nickel slag, manganese ore, and desulphurisation slag displayed notable H2-selectivity (8.7 to 10.4). It can be attributed to the presence of less-active (lattice) oxygen, limiting strong oxygen agents such as Fe2O3, Fe3O4, and Mn2O3. Moreover, desulphurization slag contained highly selective Ca2Fe2O5, which falls within the partial oxidation zone of the Ellingham diagram. Furthermore, all OC samples exhibited desirable material strength (>20 MPa), suitable for fluidised bed reactors. However, nickel, LD, and ladle slags demonstrated limited sintering with sintering onset temperatures exceeding 963 °C. This limited sintering may be attributed to the absence of iron silicates, iron-bearing aluminium silicates, manganese silicates, and potassium that contributed to the low thermal stability observed in the remaining OCs. Altogether, nickel slag calcined at 1100 °C was identified as the most promising OC material with optimal reactivity, selectivity, material strength, and minimal sintering for BCLG. Overall, this study provides a detailed and scientific methodology for OC selection and can aid future OC development.

Formation and Evolution Mechanism of the Inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in Seamless Steel Tube Steel

Herein, the formation and evolution mechanism of inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in seamless steel tube steel are investigated. In the long strip defects on the longitudinal cross section of the steel tube after the rolling bar piercing, the defect is mainly formed by Al2O3·SiO2·CaO·MgO inclusions and Al2O3·SiO2·CaO·inclusions dotted with·CaS inclusions after the rolling. The typical inclusions in the different steelmaking stages are mainly composed of CaS, Al2O3·(SiO2), CaO·(SiO2), MnS·(TiN), Al2O3·SiO2·CaO·(CaS)·(MnS), Al2O3·SiO2·CaO·MgO·(MnO), Al2O3·SiO2·CaO·MgO·(CaS)·(MnS), etc. In the billet, the average sizes of Al2O3·SiO2·CaO‐based and Al2O3·SiO2·CaO·MgO‐based inclusions are much larger than those of the other types of inclusions. Part of SiO2 in the deoxidized products SiO2 can be reduced by [Al], resulting in the formation of the Al2O3·SiO2 composite inclusions. The SiO2 in Al2O3·SiO2 inclusions can continuously be reduced by the dissolved [Ca] to form the Al2O3·SiO2·CaO composite inclusions. The SiO2 in the Al2O3·SiO2·CaO inclusions can be reduced by the dissolved [Mg] to form the Al2O3·SiO2·CaO·MgO composite inclusions. Another formation process of Al2O3·SiO2·CaO·MgO inclusions is the entrapment of ladle slag in the vacuum degassing (VD) stage, due to the strong agitation of the rising Ar bubbles in the vacuum condition of the VD stage.

Multi-model coupling-based dynamic control system of ladle slag in argon blowing refining process

Multi-model coupling-based dynamic control system of ladle slag in argon blowing refining process

Prediction of the ribbon length to determine the viscosity of ladle-refining powder containing CaF2 using inclined plane test and advanced mathematical model

ABSTRACT In the present research, the inclined plane test (IPT) and an author-developed advanced mathematical model were used to determine the viscosity of ladle-refining + CaF2 powder containing 3–10% CaF2 (LRC powder). The ladle slag powder is composed of such compounds as CaO, Al2O3, SiO2 containing percentages of CaF2 to make special changes to the chemical and physical properties of the compound. The procedure for determination of the viscosity obtained by IPT method was supported using a high-temperature viscometer. The results showed that the ribbon lengths of LRC powder obtained by using the IPT method were related to an Arrhenius relationship of viscosity. Furthermore, from the advanced mathematical relationships, it was found that there is a very close relationship between the oxygen-to-silicon molar ratio (O/Si), basic/acidic oxide molar ratio (B/A), the number of non-bridging oxygen per tetrahedrally-coordinated atoms (NBO/T), and the chemical compositions of LRC powder. Hence, the advanced mathematical relationships from the software output, and Statistical Package for the Social Sciences (SPSS), were used to determine the prediction model of the viscosity of LRC powder based on its chemical composition. This model had a very good correlation with the actual values obtained.

Clay rich river sediments calcined into precursors for alkali activated materials

Alkali activated materials (AAMs), a potential alternative to cement-based products or ceramics, can incorporate large amounts of currently landfilled aluminosilicate rich materials such as calcined clay-rich river sediments collected at hydropower plant dams. Untreated fresh sediment and untreated aged sediment intended to serve as AAM precursors were calcined to increase their amorphous content, then activated by Na or K-based silicate or hydroxide solutions and cured at 60 °C for three days.Up to 30 mass % (ma%) of fly ash (FA) or ladle slag (LS) increased the mechanical performance. The phase composition and microstructure are analyzed using X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and mercury intrusion porosimetry to gain further insight into how the additives influence the final properties of the resulting AAMs. The main crystalline components of the prepared AAMs are quartz, illite/muscovite and feldspar. The amorphous content reaches up to 52.5 ma% in the Na-activated AAMs and up to 48.8 ma% in K-activated AAMs. The acquired results confirm the suitability of the investigated sediments as sole precursors for AAMs. The mechanical properties of the AAMs can be improved by adding FA and/or LS.

Enhancing the thermal stability of alkali-activated Fe-rich fayalite slag-based mortars by incorporating ladle and blast furnace slags: Physical, mechanical and structural changes

A proper and detailed understanding of the thermal stability of Fe-rich fayalite slag-based alkali-activated materials (AAMs) is important due to their potential use in refractory and fire-resistant applications. Here, fayalite slag (FS) was used as the main precursor for AAMs. The effects of incorporating ladle slag (LS) or blast furnace slag (BFS) and different temperature exposures up to 1000 °C were investigated through visual observation, compressive strength, ultrasonic pulse velocity (UPV), thermal conductivity, x-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope coupled with electron probe microanalyzer (SEM-EPMA). The experimental results indicated that the incorporation of LS or BFS as additional calcium and aluminum sources positively affected the high-temperature behavior of blended mortars, which exhibited a reduction in voids, cracks, and thermal shrinkage while having higher residual strength and thermal stability than solely FS-based AAMs. This was mainly due to the differences in mineralogical transformation and the phases formed. Interestingly, the joint effect of elevated temperature exposure and the addition of LS or BFS enhanced the formation of more stable crystalline phases and densified the structure of blended mortars at 1000 °C.

Hydration of blended ladle slag and calcium aluminate cement

Partial replacement and co-hydration of calcium aluminate cement (CAC) with ladle slag was investigated in this study as a pathway in valorizing the slag and reducing the economic cost of CAC. The impact of this replacement on the physical and microstructural properties were analysed using different techniques such as mechanical strength test, freeze-thaw, sulfate attack, XRD, SEM etc. Thermodynamic modelling was used to predict the phase assemblages of the blended cement using the hydration kinetics of the system. Experimental results showed the reference CAC mortar and the substituted mortar exhibited comparable strength gain at 7 and 28 days, and durability as measured by sulfate attack, abrasion, and freeze-thaw resistance. A low water-to-binder ratio (0.35) lessened the effect of conversion on the hydrates, as XRD showed metastable CAH10 and C2AH7.5 as the hydrates at 7, 28 and 60 days. This however can convert later to the thermodynamically stable phase C3AH6. Thermodynamic modelling suggests these two metastable phases as major binding phases, while Si-hydrogarnet and FeOOH appeared a minor trace in the binder.*Cement chemistry notation used, where C = CaO, A = Al2O3 and H = H2O

Formation mechanism of surface upwarping and black line defects on low carbon hot rolled plate

To improve the surface quality of low-carbon hot-rolled steel plates, the upwarping and black line defects were investigated by means of XRF (X-ray diffractometer), OM (optical microscopy), SEM (scanning electron microscopy) and EBSD (electron back scatter diffraction). The results showed that the micro area compositions under surface upwarping and black line defects were mainly made of secondary oxide particles, steelmaking slag and mould flux respectively. According to the metallographic structure, inclusion compositions and grains texture analysis, it could be concluded that surface defects on hot rolled plates were attributed to the entrapment of ladle slag or mould flux, gas bubbles, micro-cracks of casting slab in the steelmaking process, rolled-in scale and unreasonable sizing press rolling parameters during the rolling process, and the position and formation process of typical surface defects on hot rolled plates were discussed in detail. Finally, it concluded that the slag entrapment and solidification hook should be controlled during continuous casting.

DISTRIBUTION OF METAL DROPLETS BETWEEN GAS AND SLAG PHASES DURING BUCKET BATH BLOWING

Losses of metal with slag falling from the surface of the molten cast iron at the loading plants after the end of the ladle desulfurization process and losses with metal drops leaving the ladle bath when gas bubbles exit and break on its surface affect the cost and energy efficiency of the operation. Blowing a mixture of dispersed magnesium with lime into the ladle bath in the conditions of cast iron desulphurization plant PrJSC "KAMET—STEEL" leads to an increase in both the viscosity and the mass of the ladle slag, with an increase in the metal content in the form of balls in the ladle slag to 65— 80 %.&#x0D; The purpose of the work is to study the peculiarities of the removal of metal drops into the surrounding space, which are formed after the bursting of gas bubbles, when they fall on the surface of the ladle bath. To realize the set goal, a series of high—temperature experiments with simulation of bath purging during bucket desulfurization of cast iron were conducted in the laboratory conditions of the Department of metallurgy of ferrous metals and pressure metal processing of DSTU. A study of the features of removal and loss of cast iron with drops during overflows of the latter shows that some of the drops explode in flight with the release of brown smoke and the formation of drops of smaller sizes than the "mother" drop. Despite favorable conditions, part of the drops reach the surface of the bath or fly beyond it without exploding. Using the obtained experimental data, a model of the release of gas bubbles on the surface of the bath and an algorithm for calculating the indicators of the movement of metal drops formed from a metal film on the surface of gas bubbles after their rupture are proposed. It was determined that the most probable condition for blowing out the bath in a 230-ton bucket is the departure of metal drops from the surface of the bath at angles in the range of 35...45 degrees. The decisive role of the physicochemical properties of the slag cover and the expediency of further improvement of the blowing mode and slag regime of ladle desulphurization of processing cast iron have been confirmed.