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42 巻, 5 号
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研究論文
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津田 昌利, 西田 脩1970 年 42 巻 5 号 p. 375-386
発行日: 1970/05/25
公開日: 2012/10/01
ジャーナル フリーIn this study the authors have investigated the influence of basic components C and Si on the oxidation behavior of Fe-C-Si alloy, the basic type of gray cast iron, at the high temperature level of 800°C in an O2 environment. The following results were obtained : It was found that there were oxidation and decarburization of the metallic matrix. We recognized that the velocity of oxidation depended on the velocity of diffusion by parabolic law. When the carbon content in Fe-C-Si alloy with about 2%Si is varied, the form, the size, the quantity and the distribution of graphite structure change. A type coarse graphite was obtained with about 3%C and D type fine graphite mixed with A type graphite structure was obtained with more 3%C. We recognized that the oxidation was greater in Fe-C-Si alloy with fine graphite than with coarse graphite, and that the size and quantity of graphite structure influenced oxidation of Fe-C-Si alloy remarkbly. After the experiment we observed that the graphite in the center of the specimen had grown we considered that the internal diffusion of C occurred at the same time as decarburization. As a natural result the addition cf graphitizing element Si in Fe-C-Si alloys with about 3%C varied quantities changes the graphite and matrix structures of these alloys. When the Si content of alloys is increased to over 4%Si, Fe-C-Si alloys with as perfect feritic matrix and a mixed graphite structures of A, C and D types were obtained. The scale formed on the surface of the specimen with under 3%Si content after the experiment consisted of three layers of different oxides. The scale was exceedingly thin in the Fe-C-Si alloys with 4%Si and with over 4%Si. The Si was dense in the scale, and therefore we considered that the diffusion of Fe was obstructed.抄録全体を表示PDF形式でダウンロード (1502K) -
片島 三朗1970 年 42 巻 5 号 p. 386-393
発行日: 1970/05/25
公開日: 2012/10/01
ジャーナル フリーFour peaks can be detected in the expansion rate curve of rapidly heated molding sand specimens to 800°C. It is considered that if the time and degree at any peak can be shown quantitatively and analyzed, the expansion mechanism under rapid heating can be clearly recognized. As a result of experiments using specimens of a new shape distinct peaks in the expansion rate curve were noted and characterized as follows : Peak 1 was due to the disagreement between the periods of the evaporation of moisture at the surface and boundary layers of the specimens, Peak 2 and 3 were due to the change of volume in transformation at the outer and inner parts of the specimens, and Peak 4 was dus to the appearance of cracks in the specimen. Finally, we concluded that the expansion rate cuve of specimens against time should be controlled by the following factors under rapid heating : (A) Accelerating Factors ; i) Increase in the rate of expansion of specimens (the change of volume in transformation of quartz is not involved) ii) Increase in the rates of the change of volume in transformation at the outer aud inner parts of specimens iii) increase in the expansion rate by the appearance of cracks in the specimen. (B) Preventig Factors ; i) Decrease in the rate of expansion due to sudden evaporation of moisture at the surface of specimens ii) Decrease in the expansion rate to a slow evaporation of moisture at the boundary layer of specimens. These factors have been schematically arranged and shown in a figure.抄録全体を表示PDF形式でダウンロード (722K) -
大出 卓, 大平 五郎1970 年 42 巻 5 号 p. 394-404
発行日: 1970/05/25
公開日: 2012/10/01
ジャーナル フリーQuite a number of papers on the spheroidization of temper carbon dealing the effects of spheroidizing elements, the amount of excess sulphur in the Mn/S ratio and mechanical stresses have been published. The authors were able to obtain spheroidal temper carbon with clear nucleus on graphitization of white cast iron without any addition of spheroidizing elements. The present investigation was conducted to find the conditions of the formation of spheroidal temper carbon. The base white cast iron used contained 3.0%C and 1.0%Si. Manganese and sulphur were added to the melt separately and the influence of them on temper carbon was studied. All the specimens were cast into a metal or a sand mold, and quenched into water during or after solidification to vary the cooling condition of the cast specimens. These were annealed in vacuum at 1,000°C and the first stage graphitization was measured by a displacement measuring apparatus. The experimental results are as follows: (1) There is a clear formation of spheroidal temper carbon when white cast iron is solidified rapidly. This may be attributed to the thermal stress in the white iron in rapid cooling. (2) Manganese content has no influence over the spheroidization of temper carbon. In contrast, sulphur exerts a strong influence, when its content is kept within one per cent. (3) The decrease of graphitization time by manganese addition is related to the aggregated temper carbon, while the increase of its time by sulphur is related to the spheroidal temper carbon. (4) The form, size, number of nodule and distribution of temper carbon influences the degree of expansion of graphitization to a great extent.抄録全体を表示PDF形式でダウンロード (1640K) -
佐藤 敬, 音谷 登平1970 年 42 巻 5 号 p. 404-410
発行日: 1970/05/25
公開日: 2012/10/01
ジャーナル フリーThe location of spheroidal graphites in Fe-C-Si and Fe-C-P alloys were investigated. Observation was made using the potentiostatic etching technique which reveals primary structures of these alloys. The results are summarized as follows; (1) Some spheroidal graphites were found in the boundaries of the flake graphite eutectic cells where Si is scarce. In low carbon Fe-C-Si alloys, particularly, the majority of spheroids were found in the interdendritic spaces. (2) The addition of Mg caused remarkable structural changes of Fe-C-P eutectic alloys, i.e. , steadite thus making the coexistence of hyper-eutectic cementite and austenite dendrite in the microregions possible. Spheroidal graphites can occur within such carbide phases and also in the eutectic devoid of austenite shells. These indicate that spheroids can grow prior to the formation of primary cementite just after Mg addition and that the presence of austenite envelope is not a prerequisite for the formation of spheroids. (3) Spheroidal graphite was also obtained in Fe-3.23%C-3.0%Si alloy containing 0.014%S which melted in alumina crucible out-of-doors in the atmosphere and cast into Cu mold from 1,500°C without any addition of spheroidizing elements. (4) From these experimental facts and published data on splat-quenching of Ni-C, Co-C, and Fe-C alloys, it is considered that the spheroidizer such as Mg not only contributes to the nucleation of graphite but also increases the tendency of non-equilibrium solidification in which case the crsytallized austenite will contain far less C than can be predicted from the equilibrium diagram. Thus in low carbon iron, spheroidal graphites may grow directly in the remaining liquid enriched in C.抄録全体を表示PDF形式でダウンロード (901K) -
木下 禾大, 竹本 義明, 松尾 英明1970 年 42 巻 5 号 p. 411-418
発行日: 1970/05/25
公開日: 2012/10/01
ジャーナル フリーTo examine various factors associated with the internal defects of iron castings, chemical composition, casting method and shape of microporosities in small specimen castings were investigated. The following results were obtained : 1. Perpendicular top gate The amount of microporosity increased with in thicker and higher carbon equivalent specimens. Regardless of thickness, the amount of microporosity decreased by a riser, but in thinner castings, it was difficult to obtain directional solidification. As for the interrelationship of shape factor, chemical composition and size of riser, larger riser was required to get soundness, when the shape was fixed and the carbon equivalent increased and also for thicker castings with equal carbon equivalent. When the riser was of equal size, the amount of microporosity increased with the decrease in shape factor. 2. Horizontal side gate In thicker castings, an inadequate size of riser led to the increase in microporosity, while in thinner castings, the effect of risering was scarcely recognized. The interrelationship of shape factor, chemical composition and size of riser was complex. With a small shape factor, the riser deteriorated the soundness of castings, and with a large shape factor, the riser began to show effect. When the shape factor was under 4, and the carbon equivalent under 3.9, soundness of castings deteriorated with a riser. But when shape factor was over 10, and the carbon equivalent over 4.0, soundness of castings was increased by riser. These rasults support empirical results that, in higher carbon equivalents, coarse grain, microshrinkage and water pressure leakage occur easily, and for platelike castings perpendicular top gate is favorable and effect of risering can be expected but it can not be expected by inadequate casting method, and therefore, that riser is not required because it has reverse effects.抄録全体を表示PDF形式でダウンロード (768K)
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