Jun Hong Chen

The Wear Mechanism Comparison between MgO-Based Chrome-Free Brick and MgO-Cr2O3 Brick in the Lower Part of RH Vacuum Degasser

The damage and improvement mechanism of rebonded MgO-Cr2O3 brick and MgO-ZrO2 brick used in the lower part of RH vacuum degasser were studied. The results show that the main damage of rebonded MgO-Cr2O3 brick is structure spalling because of the penetration of slag. MgO-ZrO2 brick has characteristics of high direct-bonding degree, small air permeability and making the viscosity of penetrated slag increased by means of ZrO2 absorbing CaO in slag to form CaZrO3 or ZrO2 solid solution, which make the degree of slag penetration decrease and improve the structure spalling resistance. MgO-ZrO2 brick has the defect of poor thermal shock resistance in use, the incorporation of MgO-rich spinel into MgO-ZrO2 brick significantly improved both thermal shock resistance and hot modulus of rupture because of the formation of eutectoid structure of grain-refining spinel and zirconia, which also improved structure spalling resistance because air permeability was decreased to 5% of MgO-ZrO2 brick

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.

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 Premelted Calcium-Magnesium-Aluminate Flux on Magnesia Carbon Brick

The novel Calcium-Magnesium-Aluminate (CMA) based premelted fluxes with different concentrations of MgO are developed and their corrosion to MgO/C brick is compared with traditional fluxing practice based on CaF2 addition. Results show that the corrosion of the MgO/C brick can be reduced obviously with initial high content of MgO employed in CMA. Additionally, the corrosion could be decreased correspondingly with the increase of MgO content in CMA fluxes, and the working lifetime of ladle slag zone can be extended by adding CMA flux.

Study on Melting Properties of CaO-Al2O3-SiO2-MgO System Calcium Aluminate Flux

Melting properties of CaO-Al2O3-SiO2-MgO system calcium aluminate (CA) flux were investigated through orthogonal design on three levels of four factors (content of CaO, Al2O3, SiO2 and MgO, respectively) to explore a reasonable chemical composition of CA flux. Results show that the softening temperature (Ts), hemispherical temperature (Th) and flowing temperature (Tf) of CA flux are influenced by the flux components in the order of SiO2 > MgO > CaO > Al2O3. The optimal chemical composition of flux is 3 wt.% SiO2, 6~12 wt.% MgO, 45 wt.% CaO and 40 wt.% Al2O3. Additionally, mineralogy composition analysis of flux clinker shows that the CA flux is mainly composed of 12CaO•7Al2O3 (C12A7), 3CaO•Al2O3 (C3A) and 6CaO•4Al2O3•MgO•SiO2 (C6A4MS, Q phase).

High Performance Iron-Rich Magnesia-Spinel Composite for Burning Zone of Cement Rotary Kiln

The structure and properties of iron-rich magnesia-spinel composite prepared using sintered iron-rich magnesia and MgO-rich spinel for burning zone of cement rotary kiln were analyzed. The results show that fine-grained magnesioferrite precipitation and magnesiowustite improved the flexibility of magnesia. The formation of Mg (Al,Fe)2O4 reaction rim between iron-rich magnesia and MgO-rich spinel by inter-diffusion reaction of Fe3+ and Al3+ improved the direct-bonded degree and high temperature strength. At high temperature, Fe3+ diffused into the grain of periclase of MgO-rich spinel and was precipitated in the from of magnesioferrite during cooling, which strengthened the structure flexibility of MgO-rich spinel. Iron-rich magnesia-spinel composite had a good adhesion property to clinker because of the uniform distribution of FeOn. Under the same content of Al2O3 and Fe2O3, the iron-rich magnesia-spinel composite had higher hot modulus of rupture, better thermal shock resistance and adhesion property to clinker compared to MgO-spinel composite and MgO-hercynite composite.

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.

Mechanism Analysis of Synthesizing Fe-Si3N4 by Flash-Combusting FeSi75

It is necessary to know the synthesis mechanism of Fe-Si3N4 by flash-combusting FeSi75 in order to control the phase composition and microstructure of Fe-Si3N4 composites. In this paper, Fe-Si3N4 and starting material FeSi75 were analyzed with XRD, SEM and EDS. The results show that Fe-Si3N4 synthesized by flash-combusting FeSi75 (≤0.074 mm) is composed of β-Si3N4, α-Si3N4, FexSi, and SiO2, in which β-Si3N4 and α-Si3N4 are from the nitridation of metal silicon and part of the silicon in ξ phase while FexSi is from the nitridation of ξ phase; during the nitridation of ξ phase, Si content declines gradually, when Fe: Si is close to 3, the nitriding reaction tends to balance; the loose accumulation of nitriding products results in the slow heat release, which makes α-Si3N4 transform to β-Si3N4 and β-Si3N4 grow further to form rod-like β-Si3N4 crystals of high slenderness ratios; the rapid quenching of nitriding products helps to keep the proportion between α-Si3N4 and β-Si3N4 small particles, and to reduce the crystallization of rod-like β-Si3N4; The grain size and distribution of FexSi in Fe-Si3N4 are related to the particle size and distribution of ξ phase in the starting material.