EFFECT OF SILICON ON PRODUCING DUCTILE IRON WITH COMPLEX STRUCTURE OF BAINITE AND MARTENSITE

This paper deals with an important role of silicon in producing ductile iron with quenched complex structure of bainite and martensite. The samples are cast in permanent mold and quenched in solution of sodium silicate. The result of thc experiments shows that the austenizing temperature should rise with increasing silicon content, otherwise much undissolved ferrite is present in the matrix after quenching. However the undissolvec ferrite can be decreased greatly or even eliminated by adding appropriate amount of ooron. On this condition, the amount of bainite gets increasing and the amount of residual austenite decreasing with the silicon cortent increasing. An approach has also been made to the mechanism of the effect of silicon on the transformation of bainite in ductile iron. The T.T.T. curves measured show that the increase of sllicon content causes the curve to shift to the left. This is quite different from the fact in steel.

Effects of CaO and Na2CO3 on the Reduction of High Silicon Iron Ores

The effects of CaO and Na2CO3 on the reduction of high silicon iron ores at 1 250 ℃ were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na2CO3, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na2CO3 were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na2CO3 was more noticeable than that of CaO, and higher Na2CO3 doses resulted in stronger inhibition of the increased metallization rate. However, when Na2CO3 was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na2CO3 were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na2CO3 dosage.

The Analysis of Silicon-iron-peach Occlusion Pigment 510B in Mossbauer Spectra

Silicon iron peach pigment 510B in Mossbauer spectra was analyed,the results show that there are mainly two kinds of iron phase mineral existing in 510B pigment,α FeO(OH) and γ FeO(OH).The Mossbauer spectra of 510B sample after being calcined in 1200℃ was also analyzed.

New insights into the effects of silicon content on the oxidation process in silicon-containing steels

Simultaneous thermal analysis（STA） was used to investigate the effects of silicon content on the oxidation kinetics of silicon-containing steels under an atmosphere and heating procedures similar to those used in industrial reheating furnaces for the production of hot-rolled strips. Our results show that when the heating temperature was greater than the melting point of Fe2SiO4, the oxidation rates of steels with different silicon contents were the same; the total mass gain decreased with increasing silicon content, whereas it increased with increasing oxygen content. The oxidation rates for steels with different silicon contents were constant with respect to time under isothermal conditions. In addition, the starting oxidation temperature, the intense oxidation temperature, and the finishing oxidation temperature increased with increasing silicon content; the intense oxidation temperature had no correlation with the melting of Fe2SiO4. Moreover, the silicon distributed in two forms： as Fe2SiO4 at the interface between the innermost layer of oxide scale and the iron matrix, and as particles containing silicon in grains and grain boundaries in the iron matrix.

Application Research of Dense Sintered Alumina in Iron Runner Castables

Three different kinds of corundum aggregates-tabular sintered alumina, dense sintered alumina, and fused dense corundum-were introduced into the silica fume .free or silica fume containing Al2O3 -SiC - C iron runner castables to investigate their influences on the flow ability, linear change on heating, bulk density, apparent porosity, cold strength, hot modulus of rupture, therm, al shock resistance, slag resistance, oxidation resistance as well as wear resistance of Al2O3 - SiC - C iron runner castables. The results show that （ 1 ） compared with the specimens with fused dense corundum, the specimens with dense sintered alumina have equivalent installation property, slag resistance and oxidation resistance, equivalent or even higher cold modulus of rupture, cold crushing strength and hot modulus of rupture, exhibiting better thermal shock resistance and cold wear resistance ; （2） adopting bimodal alumina micropowder LISAL22RABL as well as water reducers ZX2 and ZD2 can well reduce the water requirement of silica fume free castables, solving the problem of deteriorated flow ability resulted from the lack of silica fume; since the lack of silica fume avoids the formation of low melting point liquid, the hot modulus of rupture and the thermal shock resistance of the silica fume free castables are both better than those of the silica fume containing castables ; （3） the density of the castable specimens with dense sintered alumina is 4% -6% lower than that of the castable specimens with Jhsed dense corundum so the refractories consumption of one iron runner reduces by 5% by using the tastable with dense sintered alumina, which obviously reduces the cost of refractories.

Synthesis and characterization of Fe_3O_4@SiO_2 magnetic composite nanoparticles by a one-pot process

Fe3O4@SiO2 core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe3O4@SiO2 core–shell structures from prepared Fe3O4 nanoparticles. The properties of the Fe3O4 and Fe3O4@SiO2 composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe3O4 particles were approximately 12 nm in size, and the thickness of the SiO2 coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe3O4@SiO2 powder（34.85 A·m^2·kg^–1） was markedly lower than that of the Fe3O4 powder（79.55 A·m^2·kg^–1）, which demonstrates that Fe3O4 was successfully wrapped by SiO2. The Fe3O4@SiO2 composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.

Corrosion-wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

The corrosion-wear behavior of a nanocrystalline Fe_（88）Si_（12） alloy disc coupled with a Si_3N_4 ball was investigated in acid（pH 3） and alkaline（pH 9） aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe_（88）Si_（12） alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe_（88）Si_（12） alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe_（88）Si_（12） alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si_3N_4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe_（88）Si_（12） alloy in the pH 9 aqueous solution.

浅谈铜冶炼渣中横膈膜形成机理与消除实践

本文利用电学显微镜分析了电炉横膈膜的物相成分及铜损失形式,探究了电炉横膈膜的形成原因,对比了投入碳还原剂、生铁、石英石消除横膈膜的效果。发现将渣中Fe/SiO_(2)控制在1.0以下时可有效抑制横膈膜的产生,电炉渣含铜品位从最高1.09%最低降至0.36%。