Refining Slag Research Articles

Effect of Refining Slag Composition on the Cleanliness of Oriented Silicon Steel

To improve the cleanliness of oriented silicon steel, industrial experiments are performed under different refining slag composition conditions. The results show that the use of medium‐basicity refining slag (w(CaO)/w(SiO2) = 2.3–2.6, w(CaO)/w(Al2O3) = 2.3–2.6) results in higher steel cleanliness with lower Al2O3 volume fraction, and smaller inclusions. In addition, the thermodynamic equilibrium between the oriented silicon steel slag and the molten steel is investigated at a temperature of 1873 K (1600 °C) to understand the effect of different slag compositions on the oxygen content and Al2O3 absorption capacity. Furthermore, a mathematical model is introduced to describe the behavior of inclusions at the steel–slag interface as well as to predict the removal of oxide inclusions during the slag‐refining process. The experimental and predicted results for inclusion removal after slag refining are in good agreement.

Effect of CaO/Al2O3 Ratio in Fluorine‐Free Refining Slag with Low Basicity on the Cleanliness of SWRS82B Steel

A fluorine‐free quaternary CaO–Al2O3–SiO2–MgO refining slag for SWRS82B coil steel is studied by considering the requirements of the steel wire. Laboratory experiments are conducted to study the equilibrium and kinetics of steel–slag reactions. The physical and chemical properties of refining slags, including the melting temperature, viscosity, and MgO solubility, are estimated by FactSage7.2 calculation. The cleanliness of SWRS82B steel refined by slags with a basicity of 1 and C/A ratio in the range of 1.36–7.13 is studied systematically. The plasticity of inclusions is studied by phase diagram and Young modulus calculation. Deoxidizing capacity and desulfurization capacity of refining slags are discussed by kinetic calculation of steel–slag reactions based on FactSage7.2 macro‐editing and the kungliga tekniska högskolan model. Slag with a composition of 42%CaO–47%SiO2–4%Al2O3–7%MgO has the best refining effect, in which impurity elements are lowest and plastic inclusions with the smallest size and least quantity are obtained. The impurity elements oxygen and sulfur in steel can be controlled for 29 and 75 ppm, respectively. The average size of inclusions is 1.54 μm. The majority of inclusions are in a liquid state at 1600 °C and Young modulus of the inclusions ranges from 99.78 to 152.87 GPa.

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.

Effect of K2O and Na2O in Refining Slag on Non-metallic Inclusions in Tire Cord Steel

Effect of K2O and Na2O in Refining Slag on Non-metallic Inclusions in Tire Cord Steel

Removal of Residual Element Antimony from Molten Steel by CaC2-Containing Refining Slag

Increasing the use of steel scrap and enhancing its recycling utilization are important strategies for fostering the low-carbon and environmental-friendly growth of the iron and steel industry in China. However, the current steelmaking processes cannot efficiently remove the residual elements in the scrap, such as Cu, Sn, As, and Sb. As a result, the above elements are recycled and accumulate in the scrap, which will eventually have a negative impact on the properties of steel. Currently, there are few studies on Sb removal from molten steel. To remove the residual element Sb in molten steel, the CaO-SiO2-Al2O3 refining slag system containing CaC2 was used, and the effect of the CaC2 content in the molten slag, slag quantity, smelting temperature, and initial Sb and C contents in molten steel on the Sb removal ratio in the steel was investigated, and the mechanism of Sb removal by the aforementioned refining slag system was discussed in order to provide some experimental and theoretical basis for industrialization practice. When the smelting time is 5~10 min, the removal ratio of Sb from molten steel is at its peak and can reach 45.8%. The ”Sb-reversion” phenomenon will appear in the molten steel when the smelting period is progressively extended. In molten steel, CaC2 will preferentially react with O and S, and as the smelting temperature decreases, the distribution ratio of Sb, LSb, improves. An increased initial Sb content in molten steel and slag quantity are beneficial to improving the removal ratio of Sb, but an increased initial C content in molten steel is detrimental to the progress of the Sb removal reaction. The removal reaction of Sb from molten steel by CaC2 is a reversible reaction, and the diffusion of the products from the interface is the limiting factor of the overall reaction.

Kinetics Study on the Leaching of Copper from Calcification Roasting Copper Refining Slag Using Waste Acid

Kinetics Study on the Leaching of Copper from Calcification Roasting Copper Refining Slag Using Waste Acid

Study on Effects of Refining Slag on Properties and Hydration of Cemented Solid Waste-Based Backfill.

This study used refining slag (RS), ground granulated blast furnace slag (GGBS), steel slag (SS), and desulfurized gypsum (DG) to prepare a mine-filling cementitious material. The developed cementitious material and tailings sand were mixed to prepare a novel mine backfill material with better performance and a lower cost. The macroscopic properties and hydration mechanism of the cemented solid waste-based backfill were investigated when RS content was 0, 5%, 10%, 15%, 20%, 30% and 40%. The results showed that introducing RS could reduce the bleeding rate and shorten the setting time of backfill slurry while significantly enhancing the 3-day compressive strength of backfill. Compared to JL-0, the bleeding rate decreased by 50.3% as the RS content was raised to 15%, while the setting time was shortened by 36.5%, and the 3-day compressive strength increased by 4.3 times. As the RS content did not exceed 20%, the 28-day compressive strength of the backfill was not lower than that of the cement backfill (4.3 MPa). The results of microanalysis (including XRD, FT-IR, SEM, TG-DSC, and heat of hydration) revealed that the hydration products of the RS-GGBS-SS-DG quaternary material are primarily C-(A)-S-H gels and AFt. The main effect of RS is to improve the content of aluminates, accelerating and increasing the production of AFt, thus leading to faster overall hydration. This research can provide data support for the application of RS in the mine-filling field. Applying quaternary solid waste-based cementitious materials in the mine-filling field has good economic benefits.

Performance optimization and hydration mechanism of a clinker-free ultra-high performance concrete with solid waste based binder and steel slag aggregate

This study focuses on the feasibility of preparing clinker-free ultra-high performance concrete with solid waste based binder and steel slag aggregate. The influence of refining slag (RS) content, gypsum (DG) content, ground granulated blast furnace slag–hot stifle steel slag (GGBFS–HSSS) ratio and binder–sand ratio on the strength of UHPC were studied by orthogonal test, and then mainly discusses the reaction mechanism and hydration products of four solid wastes to further optimize the performance of clinker-free UHPC. The results showed the compressive and flexural strength of the Y1 samples could be increased to 108.39 MPa and 37.22 MPa respectively by optimizing RS content to 5%, DG content to 20%, GGBFS–HSSS ratio to 3:1, binder–sand ratio to 0.8. According to microanalyses (including XRD, semi-QXRD, FT-IR, TG-DSC, and SEM-EDS), the predominant hydration products of Z1 samples were ettringite and C–(A)–S–H gels, generated by the synergistic reaction of RS, GGBFS, HSSS and DG. In the first 2 days of curing, approximately 12.1% C12A7 and 1.3% gypsum was rapidly consumed, and 20.8% ettringite was simultaneously generated, which demonstrated the early strength was provided by the hydration of RS. During the 3–28 days curing, gypsum and Ca/(Si+Al) molar ratio of gels decreased by 10.9% and 0.61 respectively, and the weight loss rate was 3.85%, which indicated that gypsum reacted synergistically with HSSS and GGBFS during the process, resulting in the formation and growth of a large amount of C–(A)–S–H gels. The gels and ettringite intermingled together, making the structure more compact and the strength of UHPC increased.

Thermodynamics of Impurities Removal From Si–Fe Alloy by CaO–Al2O3–SiO2–Na2O Slag Refining

Thermodynamics of Impurities Removal From Si–Fe Alloy by CaO–Al2O3–SiO2–Na2O Slag Refining

Reaction Mechanism of CA6, Al2O3 and CA6-Al2O3 Refractories with Refining Slag.

In this study, to clarify the corrosion mechanism of CA6 based refractory by refining slag, the static crucible tests for CA6, CA6-Al2O3, and Al2O3 refractory, were carried out and the detail reaction processes were analyzed from the perspective of thermodynamic simulation and structural evolution. From the results, CaAl4O7 plays a vital role in the slag corrosion resistance of the three refractories. Regarding CA6 refractory, the double pyramid module in CA6 crystal structure was destroyed very quickly, leading to the rapid collapse of its structure to form the denser CaAl4O7 in high amounts. As a result, a reaction layer mainly composed of CaAl4O7 formed, which effectively inhibited the slag corrosion, so CA6 refractory exhibits the most excellent slag corrosion. Meanwhile, the formation of CaAl4O7 can also avoid CA6 particles entering the molten steel to introduce exogenous inclusions. For Al2O3 refractory, the generation of CaAl4O7 is much slower than that of CA6 and CA6-Al2O3 refractory, and the amount generated is also quite small, resulting in its worst slag corrosion among the three crucibles. Therefore, CA6 based refractory has excellent application potential in ladle refining and clean steel smelting.

Effects of Typical Components on Physicochemical Properties of Refining Slag and Sulfur Migration Enhanced by Electric Field

Effects of Typical Components on Physicochemical Properties of Refining Slag and Sulfur Migration Enhanced by Electric Field

Design of Refining Slag Based on Structural Modifications Associated with the Boron Removal for SoG-Si.

Solar grade silicon (SoG-Si) is the core material of solar cells. The removal of boron (B) has always been a challenge in the preparation of high purity Si. Slag refining has always been considered as one of the effective methods to remove B, but the design of refined slag has been limited by the cognition of the relationship between slag structure and impurity removal, and can only rely on the apparent basicity and oxygen potential adjustment of slag based on a large number of conditional experiments. In order to clarify the B removal mechanism of slag refining from Si, nuclear magnetic resonance (NMR) and Raman vibrational spectroscopy were used to investigate in detail the behavior and state of B and aluminum (Al) in the SiO2–CaO–Al2O3–B2O3 slag. The role of the degree of B–Si cross linking on the B activity in slag was highlighted by comparing the partition ratio (LB) between slag and Si. Q2 structural unit of slag is an important site for capturing B. BO4 (1B, 3Si) species is the main form of connection between B and silicate networks, which determines the activity of B in the slag. The addition of Al2O3 into SiO2–CaO slag can change the relative fraction of Q2 and BO4 (1B, 3Si). Increasing Al2O3 content from 0 to about 20 wt% can lead to the overall increase of Q2 population, and a tendency to decrease first and then increase of BO4 (1B, 3Si) fraction under both basicity conditions (0.6 and 1.1). When Al2O3 content is less than 10 ± 1 wt%, the decrease of BO4 (1B, 3Si) population plays a major role in deteriorating the connectivity between B and aluminosilicate network, which leads to a higher activity of B. When the Al2O3 content is greater than 10 ± 1 wt%, B is incorporated into the silicate network more easily due to the formation of more Q2 and BO4 (1B, 3Si), which contributes to a rapid decline in activity of B in slag.

Oxidation Kinetics and Mechanism of Boron in Metallurgical-Grade Silicon Melt by CaO-SiO2 Slag Refining

Oxidation Kinetics and Mechanism of Boron in Metallurgical-Grade Silicon Melt by CaO-SiO2 Slag Refining

Effects of Refining Slag on Transformation and Removal of Inclusions in Type 430 Stainless Steel

Effects of Refining Slag on Transformation and Removal of Inclusions in Type 430 Stainless Steel

Effect of Al2O3 in Refining Slag on the Cleanliness and Fatigue Property of Ultra-low-carbon Automotive Steel

The influence of Al2O3 content in refining slag on the cleanliness and fatigue property of ultra-low-carbon (ULC) automotive steel were investigated based on the industrial experiments. The inclusion-adsorption capacity of the refining slag was calculated and the total [O] (T.O) content of ULC automotive steel was measured. The number density, size distribution and morphology of inclusions were analyzed and their effects on the cleanliness and fatigue property of ultra-low-carbon (ULC) automotive steel were investigated. The results showed that as the Al2O3 content in refining slag increased from 19.92% to 39.73%, the inclusion-adsorption capacity of ULC automotive steel decreased from 210.30 down to 57.12, and the fatigue life from 1.4x104 down to 0.9x104 cycles, while the T.O content of steel increased from 12 up to18 ppm and the inclusion number density from 4 up to 9 per mm2.

Interfacial reactions between impurities and slag onset of Si purification by slag addition

The interfacial reactions between impurities (Al and Ti) and slag onset of Si purification by 51 mol% SiO2–34 mol% CaO–15 mol% MgO slag addition were studied to enhance impurity removal efficiency from Si. The Al distribution behavior at the Si/Slag interface was investigated; a short reaction time (10 s) resulted in the formation of successive SiO2–CaO–MgO–Al2O3 layers in the slag with a thickness of 10 µm; increasing the reaction time (60 s) resulted in the entire ternary slag being changed into SiO2–CaO–MgO–Al2O3 quaternary slag due to the diffusion of Al2O3. It was shown that the highest impurity removal rate of Al could be achieved at the onset of the slag refining process. Based on the Ti distribution at the Si/slag interface, the slag refinement with 51 mol% SiO2–34 mol% CaO–15 mol% MgO had no effect on Ti removal.

Effect of Medium Basicity Refining Slag on the Cleanliness of Al-killed Steel

Effect of Medium Basicity Refining Slag on the Cleanliness of Al-killed Steel

Influence of Hydrothermal Pretreatment Temperature on the Hydration Properties and Direct Carbonation Efficiency of Al-Rich Ladle Furnace Refining Slag

The influence of hydrothermal pretreatment temperature on the hydration products and carbonation efficiency of Al-rich LF slag was investigated. The results showed that the carbonation efficiency was strongly dependent on the morphology of hydration products and the hydration extent of the raw slag. Hydrothermal pretreatment at 20 °C or 80 °C favored the formation of flake-shaped products with a higher specific surface area and therefore resulted in a higher CO2 uptake of 20 °C and 80 °C-pretreated slags (13.66 wt% and 10.82 wt%, respectively). However, hydrothermal pretreatment at 40 °C, 60 °C or 100 °C led to the rhombohedral-shaped calcite layer surrounding the unreacted core of the raw slag and the formation of fewer flake-shaped products, resulting in a lower CO2 uptake of 40 °C, 60 °C and 100 °C-pretreated slags (9.21 wt%, 9.83 wt%, and 6.84 wt%, respectively).

Generation of Pyroxene-Based Porous Ceramics from Steel Refining Slag

In this paper, porous ceramics were prepared by controlling the composition and sintering temperature of raw materials based on slag from steel refining operations and without the need for a pore-forming agent. Solid-state processing included a phase transformation from low-density raw materials (2.10–2.90 g/cm3) to high-density pyroxene-based ceramics (3.22–3.88 g/cm3). Phase transformations and densification of porous ceramics were investigated by means of mercury intrusion, XRF, SEM and EDS. Results showed that a porous ceramic with optimum properties produced from raw material containing 35 wt.% steel refining slag, exhibited a high water absorption capacity of 31.62%, flexural strength of 18.26 MPa, porosity of 44.5% and an average pore diameter of 1.27 µm. Raw materials with high fineness or content near the pyroxene composition promoted formation of pyroxene and accordingly more volumetric shrinkage which enhanced both bending strength and porosity of the porous ceramics.

Molecular Dynamics Study of Structural Properties of Refining Slag with Various CaO/Al2O3 Ratios

SiO2-Al2O3-CaO-MgO is the main type of refining slag in a ladle furnace. Here the effects of the CaO/Al2O3 mass ratio on the structural properties of the refining slag system are studied by molecular dynamics simulations. The pair distribution function, coordination number, micro-structure unit and diffusion capacity were analyzed. An increase in the CaO/Al2O3 ratio did not change the bond lengths of these units. However, an increase of the CaO/Al2O3 ratio caused more charge compensators to be introduced into the refining slag system, which led to conversion of free oxygen and non-bridging oxygen to tricluster oxygen and bridging oxygen in the system. Moreover, this augmented the content of relatively stable 4- and 5-coordinate Al. As the micro-structure of the system became more complex, the overall diffusion capacity of the refining slag became poorer. In the micro-structure, the diffusion capabilities of different atoms decreased in the following order: Mg > Ca > O > Al > Si.