Wen Dong Xue

Study on High Performance Fe3Si-Si3N4-SiC Composite Preparation and its Application in Blast Furnace

Excellent Fe3Si-Si3N4-SiC composites were successfully prepared with FeSi75 and SiC as main starting materials by nitridation reaction(at 1300°C for 8Hrs). The effect of ferrosilicon alloy addition amount on material properties was studied; the ferrosilicon nitridation mechanism was analyzed through chemical thermodynamics; phase composition, microstructure, alkali resistance of products were also investigated. The results show that when ferrosilicon addition amount is 12wt%, the comprehensive property of Fe3Si-Si3N4-SiC is the best. The nitridation products are fiber-like α-Si3N4 and rod-like β-Si3N4, which makes better mechanical behavior due to fiber reinforcement; a great deal of Fe3Si intermetallic compounds uniformly distribute in matrix, which is one of the products of Fe-Si nitridation and as a plastic phase forming in grain boundary optimizes the performance of products. Chemical thermodynamic analysis shows that the fiber-like α-Si3N4 is formed by SiO(g) and N2(g) reaction which also increases the rate of nitridation. Fe3Si-Si3N4-SiC material has good performance. Now it has been successfully applied to one 2000M3 domestic steel plant, the blast furnace operation goes well.

Distribution Status of Trace Oxygen in Fe3Si-Si3N4

The distribution status of trace oxygen in the ferro-silicon nitride (Fe3Si-Si3N4) was investigated at the present, which was prepared by flash combustion synthesis method from FeSi75. The results showed that while the grain size of FeSi75 used in preparing Fe3Si-Si3N4 was less than0.074 mm, “active oxidation” occurred firstly, silicon was oxidized to form gaseous SiO(g), oxygen partial pressure was reduced in the system, silicon reacted with nitrogen directly to form Si3N4 while the system oxygen partial pressure approached less than 10-19MPa (T=1823K). O2(g) promoted the formation of Si3N4, Gaseous SiO(g) finally reacted with nitrogen and Si to form Si2N2O. The ferro silicon nitride was characterized by X-ray diffractometer and scanning electron microscope, the distribution of Si2N2O was uneven in the silicon nitride, and Si2N2O mainly distributed around Fe3Si or near the hole.

Effect of Sintering Pressure on Mechanical Properties of BN-Si3N4 Ceramic Composites Prepared by Spark Plasma Sintering

BN-Si3N4 composite ceramic wave-transparent materials with excellent mechanical properties were prepared by spark plasma sintering (SPS) using h-BN and α-Si3N4 powders as raw materials, Al2O3 and Y2O3 as sintering aids. The influence of sintering pressure on density and mechanical properties of BN-Si3N4 composite ceramics were studied. The phases were observed by X-ray diffraction (XRD), and the microstructures were identified by scanning electron microscopy (SEM). The results showed that with the sintering pressure increases, the relative density, bending strength and fracture toughness of the composite ceramics were significantly increased, and the porosity decreased rapidly. The effects of pressure on the properties of the composite ceramics was not significant at >40MPa, so 40MPa is optimal for the composite ceramics to gain good overall performance, i.e. the relative density was 89.1%, the porosity was 2.3%, the bending strength reached 215.4 MPa, and the fracture toughness was 3.1/MPa·m1/2.

Influence of Si3N4 Adding on the Performance of Al-Al2O3 Composite

Al-Si3N4-Al2O3 composite was prepared using tabular corundum, white fused corundum,α-Al2O3 fine powder and Si3N4 fine powder as raw materials and phenolic resin as low temperature binder under nitrogen atmosphere at 1 300 °C for 8 h. The results show that the main reinforced phase of Al-Al2O3 is Al4O4C in Al-Al2O3 specimens without Si3N4 fine powder adding,the main reinforced phase of Al-Si3N4-Al2O3 is SIALON while small quantity of Al,Si plastic phase presents in Si3N4 adding Al-Al2O3 specimens. Si5AlON7(Z=1) is formed in Al-Si3N4-Al2O3 specimens at low temperature (1 300 °C), which presents good comprehensive properties.

Effect of Refractory᾽s Thermal Expansion Coefficient on the Stress Field of the Top of Gasifier

The top of COREX-C3000 gasifier was simulated with a finite element analysis technique. It is studied of the influence of thermal expansion coefficient of the refractories on the temperature field and stress field and the function discipline with different parameters. The results of the simulation indicated that when the coefficient of thermal expansion of working lining and permanent lining are respectively 3.5×10-6/K and 4.5×10-6/K, the distortion and initial stress of the gasifier top are much less.

Effect of Refractory᾽s Thermal Conductivity on the Thermal Stress Field of the COREX Gasifier Top

The top of COREX-3000 gasifier was numerical simulated and investigated the relationship between thermal conductivity and the thermal-stress field. It is concluded that when the thermal conductivity of the working lining and permanent lining is respectively 0.95W / (m•K) and 0.5 W / (m•K), the change rate of the top stress along radical direction is minimum.

Effect of Slit Structure of Purging Plug on Stress Field

The three-dimensional model of purging plug was analyzed by the finite element method. The influence of slit structure (length, width, center radius and numbers) on the maximum principal stress was Contrastive studied in argon blowing process under the same boundary conditions.

Effect of Brown Corundum Dust Powder on the Sintering Performance of Corundum-Silicon Nitride Castable

The sintering performance of corundum-silicon nitride castable with brown corundum dust powder added was studied in this paper to provide a theoretical basis for the reuse of this waste powder. Waste powder, corundum, silicon nitride and silicon carbide were used as raw materials in this experiment. The sintered samples were measured routine physical property, and analyzed the microstructure of samples by SEM. Results shows that the addition of dusting powder could promote the sintering performance of non-oxides and the formation of Sialon, and improve the physical properties of samples. But when dusting powder added over 6% of the total, there are too much liquid phases, which will reduce the fire resistance performance at high temperature, so the appropriate added amount of dusting powder should be less than 6%.

High Quality Al2O3-ZrO2-C Slide Gate Properties Adding Si-Fe Sintered by both Nitrogen and Carbon Monoxide Atmosphere

The Si-Fe (≤0.043 mm) fine powder was added to the Al2O3-ZrO2-C slide gate, and the influences of adding different Si-Fe contents (2wt%, 4wt%, 6wt%, 8wt%) are studied. Two different firing ways of nitridation and carbonazation atmosphere were used. The experimental results indicated that the addition of Si-Fe improve the physical and chemical properties of the slide gate, the performance is the best when the addition of Si-Fe is 6wt% and the properties of slide gate sintering in N2-flowing atmosphere is better than that in CO-flowing atmosphere. Si-Fe will react with nitrogen and generate Si3N4 in the N2-flowing atmosphere, while it will react with C or CO to produce SiC in CO atmosphere.

Influence of Refractory᾽s Poisson’s Ratio on the Stress Field of COREX Gasifier Top

Poisson’s ratio and elastic modulus are important parameters reflecting resistance to deformation and mechanical properties of refractory. In this paper the effect of posision’s ratio and elastic modulus on the stress field of the top of gasifier was investigated by numerical simulation. It is concluded that when for working lining poisson’s ratio is 0.15, elastic modulus is 128.8×107Pa, for permanent lining poissons ratio is 0.1, the elastic modulus of 47.7 × 107Pa, the stress of the top is smaller and it is conductive to long-time use of top refractory.