The comprehensive utilization of Baosteel steel slag

Summarizes the processes and development of Baosteel slag processing techniques such as the instantaneous slag chill （ISC） process, the tank-type hot disintegrating process and the rotary drum process. A detailed introduction of the slag comprehensive utilization at Baosteel is given. The details of Baosteel＇ s comprehensive utilization in the fields of simering materials, returned slag for steelmaking, road construction, cement production, mixed concrete, new construction materials, ground-filling materials and reinforced material for soft earth are given. Emphasis is placed on source management and ensuring that from both organizational and managerial perspectives, Baosteel＇ s slag processing techniques are safe and energy-saving, thus constantly demonstrating the issue of sustainable development.     

Equilibrium boron distribution between Fe–C–Si–Al melt and boron-bearing slag

HSC 6.1 Chemistry software (Outokumpu) and a simplex–lattice experiment design are employed in thermodynamic modeling of the equilibrium boron distribution between steel containing 0.2% C, 0.35% Si, and 0.028% Al (wt % are used throughout) and CaO–SiO₂–Al₂)₃–8% MgO–4% B₂O₃ slag over a broad range of chemical composition at 1550 and 1600°C. For each temperature, mathematical models (in the form of a reduced third-order polynomial) are obtained for the equilibrium boron distribution between the slag and the molten metal as a function of the slag composition. The results of simulation are presented as graphs of the composition and equilibrium distribution of boron. The slag basicity has considerable influence on the distribution coefficient of boron. For example, increase in slag basicity from 5 to 8 at 1550°C decreases the boron distribution coefficient from 160 to 120 and hence increases the boron content in the metal from 0.021% when L _B = 159 to 0.026% when L _B = 121. In other words, increase in slag basicity favorably affects the reduction of boron. Within the given range of chemical composition, the positive influence of the slag basicity on the reduction of boron may be explained in terms of the phase composition of the slag and the thermodynamics of boron reduction. Increase in metal temperature impairs the reduction of boron. With increase in temperature to 1600°C, the equilibrium distribution coefficient of boron increases by 10, on average. On the diagrams, we see regions of slag composition with 53–58% CaO, 8.5–10.5% SiO₂, and 20–27% Al₂O₃ corresponding to boron distribution coefficients of 140–170 at 1550 and 1600°C. Within those regions, when the initial slag contains 4% B₂O₃, we may expect boron concentrations in the metal of 0.020% when L _B = 168 and 0.023% when L _B = 139.     

Study of penetration and corrosion of olivine–periclase and periclase based tundish DVMs by molten slag

Abstract

To enhance the billet caster tundish life, this study examines the relevance of the replacement of regularly used olivine–periclase based mixes by purer MgO containing dry vibe mass (DVM). After service, tundish working lining samples were studied by scanning electron microscopy energy dispersive spectroscopy to understand the influence of MgO saturation of the adhering slag and working lining interaction with the infiltrated slag. The result showed that the tundish working lining was penetrated and corroded by the molten slag for both DVM recipes. However, an increase in MgO content in the DVM exerted a chemical filtration to the molten slag, and the higher concentration of periclase dissolved into the slag, forming a saturated layer at the slag/refractory interface that resulted in the restriction of further slag penetration, probably due to an increase in the slag viscosity.     

Slag–graphite wettability and reaction kinetics Part 1 Kinetics and mechanism of molten FeO reduction reaction

Abstract

The present paper reports results relating to the kinetics and mechanism of FeO reduction by graphite, the data being obtained from experimental investigations into the wettability of graphite by molten slag containing FeO. The rate of FeO reduction was determined by measuring the volume of CO gas formed as a result of the reduction of FeO in experiments conducted in the same sessile drop apparatus. The reduction reaction initiated by direct slag–graphite contact produces CO gas which spreads into the molten slag droplet causing foaming of the slag; further reduction of FeO proceeds mostly via indirect reduction. The rate of reduction was found to depend directly on the initial FeO content. An increase in temperature improves the rate of reaction, which has an activation energy of 112·18 kJ mol^-1. These results indicate that transport of FeO (Fe²⁺, O^2- ) in the liquid slag phase is probably the slowest step.     

Control of sulphur for spring steel killed by Si–Mn and with low basicity slag

Experiments are carried out in the case of low basicity slag for spring steel killed by Si and Mn, then the changes of the sulphur content, the sulphur distribution ratio L_S and inclusions are investigated. Finally, the effect on desulphurisation of oxygen content in molten steel, the calculated and measured lgL_S and the deep desulphurisation of the vacuum degassing station are discussed. It is found that the most sulphur in liquid steel is mainly removed during the early stage of LF refining. The average sulphur content in steel and the sulphur distribution ratio after the soft bottom-blown are 0.0047% and 115, respectively. It is very accurate and credible to use the L_S model to predict L_S. During the early stage of LF refining, to reduce the oxygen content in steel quickly is very crucial for the rapid desulphurisation of the Si and Mn killed spring steel with low basicity slag. The desulphurisation of molten steel can be further carried out during the VD refining station and it is beneficial to reduce the sulphur content for the control of sulphide in spring steel killed by Si–Mn and with low basicity slag.     

Impact of slag–refractory lining reactions on the formation of inclusions in steel

Abstract

The present study was carried out to investigate the impact of slag– refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.     

Study on control technology of slag composition for low-sulfur ＆ low-oxygen steel

为实现高品质低硫、低氧钢的生产,有效降低钢中T．0、S含量,在考虑转炉下渣、炉渣氧化性以及钢水氧活度的条件下,研究确定了用于低硫、低氧钢冶炼的CaO-Si02-A1：03精炼渣系,并结合转炉下渣改质技术以及LF精炼钢包渣成分控制技术等工艺措施,制定了低硫、低氧钢的钢包渣改质制度。采用该技术生产的27CrMoNbV等圆管坯钢达到了成品w（T．0）≤15×10,w（S）≤0．005％的水平,实现了低硫、低氧钢的生产。     

In situ studies of agglomeration between Al2O3–CaO inclusions at metal/gas,metal/slag interfaces and in slag

Abstract

Studies of inclusion behaviour at the metal/slag interface is of great importance for the steel industry in order to achieve better control of both the size and amount of the inclusions, as well as improving the steel quality and the casting process. In this work agglomeration of liquid Al₂O₃–CaO particles at both steel/argon gas and steel/slag interfaces was studied with a confocal scanning laser microscope. In addition, agglomeration of liquid Al₂O₃–CaO–SiO₂ inclusions present in the slag was investigated. The results showed that liquid inclusions more easily agglomerated to semiliquid inclusions than to liquid inclusions. Moreover, the agglomeration of liquid particles was found to be improved remarkably when the particles were present in the slag compared to when they were in the steel/slag interface.     

Relationship between tension toughness and fracture toughness of low carbon low alloy steel北大核心CSCD

Basic mechanical properties for four kinds of low carbon and low alloy steels, including S355, S275, Q345D, Q345E, were examined by means of tension toughness and plane strain fracture toughness tests at room temperature to -100 °C Test results of yield strength, tensile strengh, tension toughness, fracture toughness and ductile-brittle transition temperature for each steel were obtained for the sake of identifying the relationship between tension toughness and fracture toughness. More than 200 groups of samples were tested and analysed. It shows that there is a linear relationship between tension toughness Uk and fracture toughness J0.2BL for each steel at a tempearture which is greater than its own ductile-brittle transition temperature respectively. And this sastis-fied the requirement of the linear equation.     

Copper solubility in FeO−Fe2O3−SiO2−Al2O3 slag and distribution equilibria of Pb,Bi, Sb and As between slag and metallic copper

The solubility of copper in silica-unsaturated fayalite slags containing an average of about 8 pct Al₂O₃ was measured by equilibrating the slag with metallic copper at 1200 and 1300°C under CO?CO₂ atmospheres with oxygen potentials in the rangep _{O 2}=10^?6 to 10^?11 at. The copper solubility, which was found to be dependent upon the oxygen potential, was expressed in terms of the Fe/SiO₂ ratio, temperature and activity of CuO_0.5. The distribution of Pb, Bi, Sb and As between copper and slag was measured concurrently by doping the metallic copper. The distribution coefficient was defined by (mole fractionX in metal)/(mole fractionX in slag) assuming the FeO?FeO_1.5?SiO₂?AlO_1.5?CuO_0.5 system slag. The distribution coefficient for lead was found to be a function of the oxygen potential, and a PbO activity in the slag of 0.07±0.01 was measured over the range of 1200 to 1300°C. Dissolution of Bi, Sb and As in the slag was found to be independent of the oxygen potential suggesting atomic rather than oxidic dissolution. The observed distribution coefficient for Bi and Sb was 30. The observed distribution coefficient for As was 300, but this is subject to error up to one order of magnitude due to analytical uncertainty of slag. The data are useful in analyzing minor element behavior in copper smelting processes.     

Development of mould fluxes based on lime–alumina slag system for casting high aluminium TRIP steel

Abstract

With excellent strength and ductility properties, transformation induced plasticity (TRIP) steels are superior to ordinary commercial steels and have great application potential in the automobile industry. However, the continuous casting of TRIP steels is associated with challenges owing to its high aluminium content, approximately 0?5–1?8%. The reaction of aluminium near the steel/slag interface continuously changes the basicity of conventional lime–silica based mould fluxes causing variation in the flux physical properties between the solidifying shell and mould wall. Therefore, the heat transfer process is unstable and the surface quality of the as-cast slab is not guaranteed.

To reduce the reactivity of aluminium in TRIP steel during casting, it is suggested to replace the lime–silica based fluxes with a lime–alumina based mould flux, based on laboratory measurements and industrial trials.

The trials showed great improvement in the slab surface quality and no depression defect was noticed so far.     

Characterisation of sintering of alumina matrix–stainless steel dispersion composite and interaction between chromium,carbon and alumina during powder metallurgy process

Abstract

This paper aims to study the sintering of 316L stainless steel and alumina composites. Compositions range from 0 to 100 vol.-% steel, and the experimental procedures involve density and microstructure analysis of the samples, as well as dilatometric measurements. In this study, it is shown that reducing atmosphere debinding can lead to carbon residues. These have a negative effect on alumina densification by delaying the sintering onset. For metal–ceramic composites, densification is modified by a complex interaction involving carbon (which lowers alumina density), chromium oxide (which is documented in literature to diminish alumina densification) and stainless steel phase. Chromium carbide formation is possible for some experimental conditions (1–30% stainless steel and hydrogenated argon debinding); this mechanism, locking both carbon and chromium outside alumina phase, leads to higher sintered densities.     

Microstructural Evolution of the Interdiffusion Zone between U-9 Wt Pct Mo Fuel Alloy and Zr-1 Wt Pct Nb Cladding Alloy Upon Annealing

Diffusion couple formed between U-9 wt pct Mo and Zr-1 wt pct Nb alloys, proposed as fuel and clad materials, respectively, in nuclear research reactors, was annealed to investigate the microstructural evolution of the interdiffusion zone (IZ) as a function of temperature. A layered-type IZ microstructure was observed, the mechanism of development of which was elucidated. Mo₂Zr phase, present as dispersoids, in the U-rich part of the as-bonded IZ evolved into a continuous layer and into a “massive” morphology upon annealing. The discontinuous precipitation reaction in the matrix adjoining the Mo₂Zr phase, instigated by Mo depletion, generated lamellae of α-U phase within the γ-U(Mo,Zr) matrix. Zr-rich α-Zr(U) precipitates were observed in U-rich U-Mo-Zr matrix in the IZ next to the U-9Mo base material due to the clustering tendency of the matrix phase. The IZ next to Zr-1Nb base material comprised a “basket weave” microstructure of α-Zr laths with β-Zr(Nb,U) interlath boundaries, wherein an omega like transformation of the latter to δ-UZr₂ was also noticed. The growth rates of the IZ were orders of magnitude lower when compared with the ones reported between the compositionally similar U-10 wt pct Mo alloy and the presently used Al or Al-Si cladding alloys.     

Effect of change of slag phase on dephosphorization of ��double- slag+slag- remaining�� steelmaking technology

The microstructure and phase constituent of dephosphorization slag of ??double- slag+slag- remaining?? steelmaking technology were observed and analyzed by SEM, part of the slag were heat treatment, and the effect of the change of slag phase on dephosphorization was studied. The research results show that the phase of dephosphorization slag A1-A3 with high dephosphorization rate are composed of calcium ferrite, complex liquid silicate phase (Ca3TiFeSi3O12, Ca54MgAl2Si16O9) and 2CaO??SiO2(C2S) solid phase solution with calcium phosphate (2Ca2SiO4??Ca3(PO4)2, Ca7(PO)4(SiO4)2), the main phase of dephosphorization slag A4 with low dephosphorization rate is liquid phase, the main phases of dephosphorization slag A5 are MnFe2O4, MnV2O4, Ca12Al14O33, little phosphorus rich calcium silicate solid phase is found in both dephosphorization slag A4 and A5; the phase of dephosphorization slag A3 changes little before and after heat treatment, but the phase of dephosphorization slag A4 changes greatly after heat treatment, which changing to liquid phase and white branches like RO phase; the dephosphorization slag of ??double- slag+slag- remaining?? steelmaking technology contain many un- dissolved CaO, but little is found in decarburization slag, the formation of C2S solid phase in dephosphorization slag plays an important role to accelerate the dephosphorization reaction.     

Synthesis and dissolution of slag minerals - a study of β-dicalcium silicate,pseudowollastonite and monticellite

Leaching of slag must be limited when slag is used in other areas than landfill. As slag is composed of different minerals, the properties of slag, inter alia the dissolution, depend on these minerals. If the leaching properties of each mineral are known, counter measurements can be taken to prevent the leaching of unwanted elements. In this study, the dissolution of three common slag minerals will be examined. The three minerals; boron-stabilised β-dicalcium silicate, pseudowollastonite and monticellite were synthesised. The dissolution was measured by setting pH to 4, 7 or 10 and adding 0.05 g mineral in the size range 20-38 mm and the HNO₃ consumption required to maintain the pH level was recorded during 40 h. As expected, the dissolution increases for all minerals when pH decreases. The boron-stabilised β-dicalcium silicate was the only mineral fully dissolved at all pH levels, while pseudowollastonite and monticellite only dissolved completely at pH 4.

On doit limiter le lessivage de la scorie lorsqu'elle est utilisée en d'autres endroits que la decharge publique. Puisque différents minéraux composent la scorie, ses proprieties, parmi d'autres la dissolution, dependent de ces minéraux. Si l'on connaTt les propriétés de lessivage de chaque mineral, on peut utiliser des contre-mesures pour empecher le lessivage d’éléments indésirables.

Dans cette étude, on a examine la dissolution de trois minéraux communs de la scorie. On a synthétisé les trois minéraux, soit le silicate β-dicalcique stabilise au bore, la pseudowallonite et la monticellite. On a mesuré la dissolution en établissant le pH à 4,7 ou 10 et en ajoutant 0.05 g de minéral dans la gamme de taille de 20 a 38 mm. On a ensuite enregistré pendant 40 heures la consommation d'HNO₃ requise au maintien du niveau de pH.

Comme on s'y attendait, la dissolution de tous les minéraux augmente avec la diminution du pH. Le silicate β-dicalcique stabilise au bore était le seul minéral complétement dissous a tous les niveaux de pH, alors que la pseudowallonite et la monticellite étaient complétement dissoutes seulement au pH de 4.     

Differential rates of age of seizure onset between sexes and between hemispheres?

The American Diabetes Association and a working group of the International Diabetes Federation and the World Health Organisation are considering the possibility of lowering the level of fasting glucose for diagnosis of diabetes from 7.8 mM to 7.0 mM (126 mg/dl) and adding a "hyperglycaemia" category (6.1-6.9 mM). This report studied the resulting change in the frequency of diabetes in the French D.E.S.I.R. cohort and evaluated cardiovascular risk factors according to the proposed limits. The frequency of treated diabetes was 1.0% in this cohort of more than 5,000 French men and women 30 to 64 years of age, 0.7% had a fasting glucose > or = 7.8 mM versus 1.6% for the proposed > or = 7.0 mM. Using the new criteria, 3.8% of men and 1.6% of women would be diabetic. For many cardiovascular risk factors, men with fasting glucose > or = 7.8 mM had a significantly higher risk than those in the (7.0-7.7 mM) range, whereas no significant differences were found for women. There were few differences between the (7.0-7.7 mM) and (6.1-6.9 mM) ranges, but highly significant differences were apparent for both sexes between the normoglycaemic (< 6.1 mM) and hyperglycaemic (6.1-6.9 mM) categories. The percentage of men with two or more of ten risk factors increased with fasting glucose: 36% in the normoglycaemic (< 6.1 mM) and 49% in the hyperglycaemic (6.1-6.9 mM) categories; 73% with fasting glucose in (7.0-7.7 mM) versus 90% with fasting glucose > or = 7.8 mM. In women, the corresponding percentages were lower: 26% and 60%, 32% versus 64% respectively. The major increase in cardiovascular risk factors would appear to occur at 6.1 mM, for men, whereas the increase in the combination of risk factors was at the more conservative cut-off of 7.0 mM.     

Shock synthesis of silicides—II. Thermodynamics and kinetics

A thermodynamic and kinetic analysis of shock-induced reactions in the (Nb or Mo)-Si systems provides a framework for the extraordinary high reaction rates and a quantitative interpretation of the experimental results obtained in Part I. The thermodynamic analysis is conducted by adding the heat of reaction to the shock energy; increases in shock pressure, temperature, and velocity are predicted. At the particle level, melting at the silicon-metal interface is found to be a necessary condition for the initiation of reaction; heat conduction calculations enable the prediction of a critical molten (Si) region size for which the heat generated through the reaction exceeds the heat lost to the unreacted regions. The calculation of melt fraction (of Si) as a function of shock energy coupled with critical melt pool sizes enables the determination of a minimum shock energy for the initiation of shock-induced reaction. At the local level, the reaction kinetics can be rationalized through the production of a liquid-phase reaction product (NbSi₂), the formation of spherical nodules (∼2 μm diameter) of this product through interfacial tension and their subsequent solidification (in times of 1–5 ns). The heat generated by the reaction is sufficient to melt niobium along the interface which facilitates both the expulsion of the NbSi₂ nodules into the liquid Si, and the generation of fresh Nb interface for further reaction. In addition, the dissolved Nb enriches the surrounding Si liquid, promoting more NbSi₂ reaction and formation.     

Smelting reduction reactions by solid carbon using induction furnace: foaming behaviour and kinetics of FeO reduction in CaO–SiO2–FeO slag

Abstract

Smelting reduction process technology is progressing rapidly, and research to understand the reduction of FeO in molten slag and the associated foaming behaviour has gained importance. The present paper reports experimental data on the reduction of FeO in molten slag generated in a 30 kW capacity induction furnace. The influence of FeO content in the slag and temperature on the foaming and kinetics is discussed. The foaming index, a parameter describing the travel time of gas in the reactor, is shown to decrease with an increase in the superficial gas velocity. The quantitative dependence of the foaming index on slag properties viscosity, surface tension and density has been studied. The data have also been analysed to give an estimation of the activation energy for the reduction reaction. The reduction reaction, initiated by direct slag–graphite contact, produces CO gas, which spreads into the molten slag bath causing foaming of the slag; further reduction of FeO proceeds mostly via indirect reduction. The rate of reduction is found to depend directly on the initial FeO content. An increase in temperature increases the rate of reduction, which has an activation energy of 118 kJ mol^?1 of FeO. The results indicate that transport of FeO in the liquid phase is the rate controlling step. The major findings are in agreement with those reported by earlier investigators.