Showing papers in "Tetsu To Hagane-journal of The Iron and Steel Institute of Japan in 1995"

Gas diffusion electrode

Abstract: Disclosed herein is a gas diffusion electrode comprising a reaction layer and a gas diffusion layer attached to each other characterized in that a plurality of apertures or a concave convex surface is provided on or through the electrode to facilitate the flowing of an electrolyte. In this electrode, a large volume of an electrolyte and a gas can flow even though the interelectrode distance is small so that a reaction can be promoted to elevate the efficiency.

Influence of Heating Temperature and Strain on Surface Crack in Carbon Steel Induced by Residual Copper

Abstract: Synopsis : Mechanism of surface crack formation of steel induced by residual copper (Cu) is investigated using a new technique of Greeble test. Two kinds of experiments were carried out, to clarify the effect of temperature and to understand the behavior of crack growth. Crack is caused by liquid Cu, which precipitates at steel-scale interface during oxidation. However, no crack formed at higher temperature. Micro analysis indicates that it is due to the formation of liquid scale above eutectic temperature of FeO-2FeO¥SiO2. Liquid Cu-precipitates are trapped in the liquid scale area, and they cannot penetrate into austenite grain boundaries. The fact that silicon addition reduces the crack formation also supports this mechanism. Deformation test with various strains reveals that there exist two stages in the behavior of crack growth. At the first stage, crack grows deeper, because liquid Cu penetrates into the boundary. The crack stops growing along the depth direction and opens its width in the second stage, because of the lack of liquid Cu. That means the amount of Cuprecipitates decides the crack depth.

Separation of Non-metallic Inclusions from Molten Metal Using Traveling Magnetic Field

Abstract: Synopsis : A new method for separating inclusions from a molten metal by using a traveling magnetic field is proposed. A bundle of thin tubes for flowing molten metal is set between two linear induction motors which generates a transverse magnetic field traveling in the direction perpendicular to the molten melt flow. As the flow driven by the electromagnetic force which is induced to the traveling direction of magnetic field is constrained by the tube wall, inclusions move toward the tube wall opposite to the direction of the electromagnetic force. Two mathematical models to evaluate the electromagnetic force acting on inclusions were developed. The analytical formulations of the electromagnetic force in both the models were derived as a function of the design parameters of induction motors and the operating variables. The elimination principle of inclusions proposed here was confirmed in the experiment in a Al-Al203 system. A feasibility study on the application of the method to the elimination of inclusions from molten steel was performed.

Reaction Rates of Oxidized Iron-Scrap Briquette with Pulverized Coke in Nitrogen Atmosphere

Abstract: Synopsis : Reaction rates for the reduction of iron oxide, the gasification of coke and the thermal decomposition of the binder in oxidized iron-scrap briquettes containing pulverized coke were measured under the conditions of elevating and fixed temperatures in the nitrogen atmosphere. The reaction rates were obtained by examining the various factors affecting the reaction mechanisms. The weight change of the briquette calculated by the rate equations agreed well with experimental values. The rate equations can therefore be applied to the mathematical simulation model of a cupola process to which oxidized iron-scrap is charged as a burden material.

Effect of Testing Atmosphere on Low Cycle Fatigue of Hot Work Tool Steel at Elevated Temperature

Abstract: Effects of atmosphere and strain amplitude on low cycle fatigue behavior of AlSl H11 hot work tool steel were investigated. The fatigue life in vacuum was twice as long as that in air. From the result of the fatigue test in vacuum, it became clear that slip bands on the specimen surface were formed during fatigue and they grew up with increasing number of cycles. The initial fatigue cracks were generated at the intersection of slip bands and were vertical to loading direction. The fatigue cracks mainly initiated at internal inclusions when tested in vacuum, whereas superficial cracks were observed on the same fracture surface when applied higher strain amplitude. In contrast, nucleation sites of fatigue cracks when tested in air were specimen surface irrespective of the magnitude of strain amplitude. The extension of low cycle fatigue life in vacuum was mainly due to the decreasing of growth rate of superficial and internal cracks to the critical crack length.

Fabrications and Thermoelectric Properties of Semiconducting Iron Disilicides

Abstract: 鉄 け い 化 物 は 耐 熱 材 料 と して開 発 さ れ て き た一 連 の 金属 間 化 合 物 で1)~5), Table 1に 示 す5つ の 化 合 物 が 存 在 す る6)~32)。こ の表 に は それ ぞれ の 結 晶 構 造 と室 温 に お け る比 抵 抗,熱 電 能(Seebeck係 数)お よび ホ ー ル 係 数 を示 した が,熱 電 能 の特 別 大 き な け い 化 物 はβ-FeSi2で あ る。この け い化 物 は,半 導 体 的 性 質 を もち,熱 電 能 が 大 きい ば か りで な く, 比 抵 抗 が 比 較 的 小 さ く,し か も1200K以 上 の 高 温 の 大 気 中 に も耐 え るの で,熱 電 エ ネ ル ギ ー 変 換 に利 用 す る試 み が な さ れ29)33)~38),すで に2,3の 応 用 製 品 も市 販 さ れ て い る37)38). β-FeSi2は 高 温 の金 属 相 か ら低 温 の 半 導 体 相 に変 わ る金属 一半 導 体 遷 移 を示 す24)28)39)~43).Fig .1に 示 すPitonとFayの 状 態 図 に よれ ば鋤,Fe-66.7at%Si組 成 にお い て 共 晶 点 と包析 点 が 存 在 し,共 晶温 度1489Kと 包 析 温 度1259Kの 問 で はFesi (ε相)25)~23)とFe2Si5(α 相 †1)44)45)の共 晶 合 金 で あ るが,1259 K以 下 で は化 学 量 論 組 成 のFeSi2(β 相)に な る。また,ε 相 の Si固 溶 範 囲 は1at%以 下 で あ るが22),α相 は 共 晶 温 度 にお い て7.1~12at%のFe空 格 子 点 を もつ44)45)。 Fe-66.7at%Si共 晶 合 金 に お け るα相 の 空 格 子 点 は 約7.1at%で あ り,こ の 合 金 を包 析 温 度 以 下 で 熱 処 理 す る こ とに よ っ て,半 導 体 相 の β 一FeSi2が 生 成 さ れ る24)30)40)~4δ)。 一 方 低 温 の β相 は ,Mn33)~37)40)~42)あ る い はA124)29)46)を 添 加

Technology for Granulating Coke Breeze by Centrifugal Rolling Type Pelletizer and Effect of Granulated Coke Breeze on Sintering Operation

Abstract: Coke breeze was granulated by a centrifugal rolling type pelletizer which was operated at a Froude number (Fr) that is more than 102 times that for the conventional drum mixer. The effects of the coke breeze granulated by this new technology on the sintering opetation, the granulation of raw mix for sintering, and the quality of sinter were quantitatively studied through sintering pot test and plant test at Nagoya No. 2 Sintering Plant. As a result, the following findings were obtained:(1) In the coke breeze granulation test, the centrifugal rolling type pelletizer could not only granulate fine coke breeze but also cause ultra-fine coke particles to penetrate into coarser particles, while preventing the granulated particles from becoming excessively coarse.(2) In the sintering pot test and sintering plant test, it was clarified that granulated coke breeze became the nuclei of quasi-particles of the raw mix for sintering and then promoted the granulation of other raw materials in the iron ore sintering process.(3) It was confirmed that this new technology could decrease NOx emissions by reducing the ratio of fine particles in coke breeze. NOx emissions could be further reduced by the addition of quick lime. It was also clarified that the reducibility of sinter was improved.