Shuigen Huang

Effect of the CaO-Al2O3-Based Top Slag on the Cleanliness of Stainless Steel During Secondary Metallurgy

The ladle treatment of a 18xa0pct Cr-9xa0pct Ni stainless steel, with desulfurization as its main purpose, was simulated on a laboratory scale. The influence of the top slag chemistry on the steel cleanliness was evaluated. A higher steel cleanliness was obtained with an optimized lime-alumina-based slag than with a lime-fluorspar-based slag. The inclusions were found to be mainly in the form of oxysulfide; the alumina content in the inclusions first increased and subsequently showed a slow drop, while the sulfide content decreased during the treatment. The equilibrium between steel and inclusions was found to be more easily reached than that between slag and steel. A slag–steel kinetic model was used to predict the steel chemistry evolution during the treatment. Furthermore, a slag–steel–inclusions interaction kinetic model was developed to calculate the change of alumina content in the inclusions during the ladle treatment. The sulfide content of inclusions was also calculated and compared with the measured values.

Modeling of nucleation and growth of M23C6 carbide in multi-component Fe-based alloy

Three-dimensional atom probe (3DAP) technique has been used to study the nucleation and growth of M23C6 carbide in a supersaturated multi-component Fe-based alloy aged at 800°C. 3D images indicate that the radius of M23C6 carbide after ageing for 10 min is about 9 nm. Concentration profiles of alloy elements in the carbide are also obtained. Combined with PANDAT and Thermo-Calc software, attempts to model the early stages of precipitation are present. The calculated particle size and composition of M23C6 carbide is in good agreement with 3DAP data.

Computer simulation of W-C-Co-V system diffusion couples

Abstract Diffusion couples, WC/Co-1 at.%C, V8C7/Co, and WC/Co-0.3wt.%V8C7 were constructed and annealed at temperatures ranging from 1100 to 1300°C. The concentration profile of V and W atoms in these couples were measured by EPMA. Aided by Thermo-calc & DICTRA software package, the concentration profiles of W and V in established diffusion couples were calculated by the moving boundary model according to revised dynamic parameters and MOB database, respectively. Then the concentration profile of W in Co binder during sintering WC-Co cemented carbide was simulated by the Cell model. It can provide reference for composition and sintering process design of cemented carbides with high performance. Meanwhile, the validity of revised dynamic parameters of the W-C-Co-V system is verified by the comparison of experimental and simulated results.

Valorization of BOF Steel Slag by Reduction and Phase Modification: Metal Recovery and Slag Valorization

Basic oxygen furnace (BOF) steel slag is a main byproduct in steelmaking, and its valorization is therefore of considerable interest, from a metal-recovery perspective and from a residue-utilization perspective. In the present study, the carbothermic reduction of BOF slag was investigated systematically. The reductions of Fe- and P-containing phases (i.e., oxide and compounds) are discussed. Effects of Al2O3 and SiO2 additions on the solidification microstructure and mineralogy associated with the reduction processes were also investigated. The formation and growth of the extracted metallic phase are discussed, and the mineralogy of the residue slag is determined. We conclude that by controlling the additions under a rapid cooling condition, it is possible to extract metallic iron as high-grade metal and simultaneously to utilize the remaining slag for construction applications.

Stabilization of Free Lime in BOF Slag by Melting and Solidification in Air

The present study reports on the mineralogy of BOF slag after melting and solidification under Ar and air atmosphere. Results indicate that free lime can be effectively stabilized in air without additional stabilizers like SiO2. The stabilization mechanism was analyzed, and the role of the oxygen partial pressure was explored. Wustite is believed to be oxidized to hematite under high oxygen partial pressure and then stabilizes the free lime by forming brownmillerite.

Computer Simulation of Fe-Al-Si System Diffusion Couples

Diffusion couples, Fe-6.8 wt% AI-1.0 wt% Si/Fe and Fe-6.3 wt% AI-0.9 wt% Si/Fe were constructed and separately annealed at 1050°C for 3 h and at 1000°C for 64 h. The concentration profiles of Fe, Al and Si atoms in these couples were measured by electron probe micro-analysis (EPMA), while the diffusion behavior was also simulated by coupling thermodynamic and kinetic properties of Fe-AI-Si system. The simulation results were in good agreement with the measured concentration profiles showing the validity of dynamic parameters of Fe-AI-Si system. Calculation was made for Fe-7 wt% Al-1 wt% Si/Fe diffusion couples at 1000°C with different diffusion time. Silicon uphill was found under the influence of aluminum.

Metal Recovery from BOF Steel Slag by Carbo-thermic Reduction

BOF steel slag is axa0main by-product in steelmaking. The valorization of BOF slag is good for the industry and the environment. In the present study, the carbo-thermic reduction of BOF slag has been investigated, the reduction of Fe and P containing phases (i.u2009e. oxide and compounds) is discussed, and the effects of Al2O3 additions on the reduction process are described. XRD and EPMA have been applied for characterizing the slag. We conclude that, by controlling the test conditions, it is possible to purify the recovered Fe.ZusammenfassungBOF Stahlschlacke ist ein wichtiges Nebenprodukt in der Stahlerzeugung. Die Verwertung von BOF-Schlacken ist gut für die Industrie und die Umwelt. In der vorliegenden Studie werden die carbo-thermische Reduktion von BOF-Schlacke, die Reduktion von Fe- und P-haltigen Phasen (d.h. Oxide und Verbindungen) und die Wirkungen von Al2O3-Zusätzen auf den Reduktionsprozess beschrieben. XRD und EPMA wurden zur Charakterisierung der Schlacke angewendet. Wir schließen daraus, dass es durch die Kontrolle der Testbedingungen möglich ist, das gewonnene Fe zu reinigen.

Freeze‐Lining Formation from Fayalite‐Based Slags

Formation of freeze-linings from aggressive process slags is used in industrial pyrometallurgical processes to protect the furnace wall. In this laboratory study, the formation of freeze-linings from fayalite-based (FeO-SiO2-Al2O3-CaO) slags was investigated. This was performed with a gas-cooled probe at 1200 °C under protective atmosphere. The microstructure of the freeze-linings formed on the samples was characterized using scanning electron microscopy (SEM). The influence of cooling rate, slag agitation and slag composition on the freeze-lining formation was studied by varying the gas-flow rate, rotating the crucible and changing the CaO and Al2O3 contents in the fayalite-based slag, respectively. The results indicate that fayalite (Fe2SiO4) precipitated from the slag and grew into large columnar crystals along the heat gradient from the cooled probe to the bath slag. The thickness of the freeze-lining increased with increasing cooling rate, while an increase in the slag agitation and the CaO and Al2O3 contents in the slag decreased the thickness of the freeze-lining. These macroscopical observations are discussed with respect to the microstructural evolution in the formed freeze-lining samples.

Numerical simulation on magnetic assembled structures of iron-based metallic particles within MMCs by a homogeneous strong magnetic field

Particle-reinforced metal matrix composites (MMCs) have excellent physicochemical properties as structural materials. The morphology and distribution control of reinforcement particles during the fabrication of MMCs are difficult-but-critical-to-achieve required properties of the materials. This research demonstrates a possibility to quantitatively control the distribution of particles in the metal matrix by applying a magnetic field. A 2D numerical model is developed and applied to evaluate the behaviour of Fe-based metallic particles in aluminum MMCs. By combination of 2D simulation with intersectional directions, this model also provides some hints for 3D practice. The assembled structure is found to be governed by the external magnetic field orientation, magnetic flux density and magnetic susceptibility of the particles. Both behaviours of particle agglomeration and dispersion are quantitatively characterized in different conditions. By using a strong magnetic field, it is found that assembled structures of weakly magnetic particles can be effectively manipulated. Therefore, it can be expected to fabricate particle-enhanced metal matrix composites/ceramics/glass with substantial improvements in physical and chemical properties by using a magnetic field.