Decrease Of Si Content Research Articles

Surface structure of conductive polypyrrole-containing composites

The surface structures of polypyrrole/silicon crosslinked poly( styrene/butyl acrylate/hydroxyethyl acrylate) (PSBH) conductive composite films were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy. It was found that the conductive composite films were of a “sandwich” structure, and the surfaces greatly differ in chemical compositions and phase morphologies from the bulk. The Si and N contents exhibit opposite gradient change with the measured depth of the two surface layers in the composite films, namely, the decrease in Si content and the increase in N content with increase in the depth of the surface layers. However, the Nδ+/N ratios in polypyrrole decreased with the measured depth of the conductive composite film. It was also found that the conductive composite film based on silicon crosslinked matrix exhibits more environmental stable than that based on linear matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 95–101, 1999

Crystallographic and magnetic properties of NdCo11−xSix compounds

The effects of substitution of Si for Co on the crystal structural stability and magnetic properties of NdCo11−xSix compounds have been studied. X-ray diffraction and magnetic measurement show that the single phase region can be expressed as NdCo9.8–9.2Si1.2–1.8 other than NdCo9Si2. X-ray-diffraction study indicates that the compounds adopt the tetragonal BaCd11-type struc- ture. The magnetic properties of a series of NdCo11−xSix solid solutions have been studied by magnetic measurement. Our investigations show that the Curie temperature of NdCo11−xSix increases drastically from 528 K (x=1.8) to 833 K (x=1.2) as the Si content decreases. The Co magnetic moment reaches a maximum between NdCo9.8Si1.2 and NdCo9.6Si1.4, and decreases with the further increase in x. The substitution of Si for Co in NdCo11−xSix leads to a contraction of lattice constant a by 0.2%, c by 0.2%, and a consequent reduction of the unit-cell volume by about 0.6%. The Rietveld refinement results show that the silicon atoms preferentially occupy the 8(d) sites. The occupation of 8(d) sites by proper amount of Si will shift the Fermi level EF upward and to a valley with a lower local density of states in NdCo11−xSix compounds, which is favorable for the stability of the BaCd11-type structure.

羽口からのフラックス吹込みによる高炉低Si操業

For the purpose of decreasing Si content in hot metal by means of flux (CaO, MgO) injection through the blast furnace tuyeres, fundamental experiments and operational tests at Keihin No. 2 blast furnace were carried out. Results obtained are as follows.(1) The generation rate of SiO gas (K'SiO) based on fundamental experiments were formularized as follows.K'SiO= 4.07 × 107 × exp (-120 × 103/RT) × αSiO2(2) For decreasing Si content in hot metal, MgO flux injection from the tuyeres was proved to be more effective than CaO flux injection. As to the charging method of flux, tuyere injection is most effective followed by top charging with coke and top charging with ore.(3) The decrease in Si content in hot metal by MgO injection was estimated to be mainly due to the decreased generation rate of SiO gas with decreased activity of SiO2 in raceway slag, which is formed by the reaction of coke ash and injected MgO flux.(4) According to magnesite injection of additional 10 kg/t from the tuyeres, Si decreases due to MgO increase in hearth slag and raceway slag were estimated to be 0.009% and 0.045% respectively.

熱風制御弁による高炉内円周バランス制御

NKK jointly with Asahi Glass Co., Ltd. have developed a Hot Blast Control Valve (HBCV) which can control the flow rate at each tuyere. 19 HBCVs out of 38 tuyeres were installed in Keihin No. 2 BF in 1986. Through various test operations, innovative technologies for blast furnace operation have been developed. This paper reports the circumferential balance control of stock line levels.(1)At the proper block with closed HBCVs, the coke consumption amount at the tuyere decreases, however the burden descending rate at the throat becomes faster. Applying these phenomena, it is Possible to control the circumferential balance of SL levels.(2)The simple stand-alone method, where the HBCVs at the block with higher SL level are closed based on the average SL levels during the past definite period of time, had sometimes put into disorder, and it was impossible to continue a stable control of SL levels.(3) For further stable control, Successive Alleviative Integration (SAINT) method has been developed, taking account of their interferences of each HBCV opening, dead time and integral action of changes in valve opening.(4)The test operation in Keihin No. 2 BF showed that it is extremely effective for the improvement of furnace conditions and decrease of Si content in hot metal to control the circumferential balance of SL levels on the SAINT method.

Desiliconization Reaction of Pig Iron with MnO Containing Blast Furnace Slag under Pressurized and Coke-coexisting Condition

For the clarification of the mechanism of the desiliconization reaction of pig iron with MnO containing blast furnace slag under pressurized and coke-coexisting condition, fundamental experiments were performed by the use of a pressurized high frequency furnace. Based on the experimental results, a mathematical simulation model with consideration of the direct reduction reaction as the coupled reaction with the desiliconization reaction was developed and applied to the quantitative evaluation of the desiliconization reaction with MnO and FeO containing slag.The following knowledge was obtained.(1) Under the existence of coke, MnO and FeO are partly consumed by the coupled reaction of direct reduction reaction and the desiliconization reaction is restrained.(2) The increase of pressure, with the presence of coke, results in the indirect enhancement of the desiliconization reaction through the restraint of the direct reduction reaction.(3) The effect of the charging of manganese ore on the increase of Mn content and the decrease of Si content in pig iron was quantitatively evaluated by an another simulation model for blast furnace hearth.

小型燃焼炉におけるレースウェイ領域での吹込み鉱石粉の伝熱と反応

Influence of injected ore fines on the chemical and physical phenomena in and around the raceway was examined and the mechanism of silicon decrease in iron melt was experimentally investigated by using a small-scale hot furnace.(1) The temperature in the raceway decreases with increasing the amount of injected ore fines mainly due to the endothermic reaction(2) A part of injected ore fines remains inside of the raceway and shows high fractions of melting and reduction. Both fractions of sample increase with the increase of the injection rate, as the proportion of remaining ore also increases.(3) SiO content in the gas and Si content in the metal in the dripping region above the raceway decrease with increasing the injection rate, since SiO gas generated in the raceway can be absorbed by injected iron ore at the molten state.(4) Decrease of Si content in the metal by the reaction with FeO in slag formed by injected ore is negligibly small in the dripping region below the raceway.

コークス共存,加圧下におけるMnO含有高炉スラグによる脱珪反応

For the clarification of the mechanism of the desiliconization reaction of pig iron with MnO containing blast furnace slag under pressurized and coke-coexisting condition, fundamental experiments were performed by the use of a pressurized high frequency furnace. Based on the experimental results, a mathematical simulation model with consideration of the direct reduction reaction as the coupled reaction with the desiliconization reaction was developed and applied to the quantitative evaluation of the desiliconization reaction with MnO and FeO containing slag.The following knowledge was obtained.(1) Under the existence of coke, MnO and FeO are partly consumed by the coupled reaction of direct reduction reaction and the desiliconization reaction is restrained.(2) The increase of pressure, with the presence of coke, results in the indirect enhancement of the desiliconization reaction through the restraint of the direct reduction reaction.(3) The effect of the charging of manganese ore on the increase of Mn content and the decrease of Si content in pig iron was quantitatively evaluated by an another simulation model for blast furnace hearth.

Precipitation behavior of laves phase and its effect on toughness of 9Cr-2Mo Ferritic-martensitic steel

This study clarified the ralationship between the toughness of a 9Cr-2Mo dual phase steel and precipitates formed during aging, with special attention to the Laves phase (Fe 2 Mo). The ductile-brittle transition temperature (DBTT) is increased and the upper shelf energy decreased when the Laves phase begins to precipitate during aging. Electron microscopy and X-ray diffraction indicate that elimination of Si in the steel reduces the precipitation of the Laves phase and results in maintaining good toughness. It is also noted that the toughness of the steel is controlled by the total amount of precipitates (Laves + carbides) in the aging at 873 K for more than 3.6 × 10 3 ks. A time-temperature-precipitation diagram for the Laves phase is established and it clearly shows that the precipitation of the Laves phase is markedly retarded by the decrease of Si content. In Si-free steel, no Laves phase is observed in the temperature and time range investigated.

Effects of Alloying Elements on the Rotating Bending Fatigue Properties of Carburized Steels

A study was made on the effects of alloying elements such as Si, Mn, Cr, Ni and Mo on the rotating bending fatigue properties of carburized steels. At first, the effect of Si was studied using commonly used grades, JIS SCM420 and SNCM420. It was shown that the decrease in Si content remarkably reduced internal oxidation and resulted in higher fatigue strength. In order to clarify the effects of other alloying elements, fatigue tests were carried out on low Si steels where the Si contents were less than 0.15%. Internal oxidation was reduced and fatigue resistance was improved with increasing Ni and Mo contents and with decreasing Cr and Mn contents when keeping the core hardness constant. The 0.2%C-3%Ni-0.45%Mo steel showed the highest fatigue limit of 100kgf/mm2. High Ni-high Mo-low Mn-low Cr steels are considered to exhibit superior fatigue resistance by supressing internal oxidation and by the greater fracture toughness of carburized case.