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48 巻, 11 号
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研究論文
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柳沢 平, 丸山 益輝1976 年 48 巻 11 号 p. 681-686
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーThe effects of sulfur and cooling rate on the growth of graphite crystals from carbon saturated Fe-C-Si melts were studied experimentally by crytal pulling method. Graphite of a pile of flaky crystals with rotational grain boundaries were grown and the angles of rotation agreed with the values calculated by the lowest boundary energy theory. This is one of the important evidences of crystal growing on the basal plane by the mechanism of screw dislocation. The rotational grain boundaries relax the strains around the screw dislocations forming growing steps on the interface. By increasing the pulling rate and decreasing sulfur contents of the melts, the density of the growing sites on the basal plane increased extremely. It was considered that the growth normal to the basal plane was interrupted by the pinning of adsorbed sulfur on the growing steps.抄録全体を表示PDF形式でダウンロード (820K) -
大井 利継, 藤岡 稔1976 年 48 巻 11 号 p. 687-693
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーThe authors have shown in the previous paper that the carbide metastabilizing tendency of hyper-eutectic melts of ductile cast iron decreased remarkably as the contents of carbon and silicon were increased. In this study, some experiments were made to apply this effect to the welding of cast iron. The carbide metastabilizing tendency was investingated in a case where the ductile cast iron containing 4.5%Si and CEs value (≃%C+0.31%Si) of 5.1 was melted quickly and cooled immediately by imitating the heat cycle of welding rod. When the melting temperature rose above the primary liquidus temperature, the carbide metastabilizing tendency increased suddenly. However, when the melting temperature was below the liquidus temperature, cementite was not formed at all within the region of five seconds of the solidification time. Build-up welding test was carried out on a ductile graphite cast iron plate by oxygen-acetylene gas method, using welding rods of Si3∼5% and CEs value of 5.1. When welding was carried out with special care not to heat the molten pool above the liquidus, sound weld structuut without any cementite was obtained if the silicon content of the welding rod was more than 4%. It was not necessary to preheat the plate to a high temperature in order to delay the cooling rate.抄録全体を表示PDF形式でダウンロード (972K) -
近藤 靖彦, 安江 和夫, 磯谷 三男1976 年 48 巻 11 号 p. 694-699
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーThe solidification behaviour of Fe-2.7%C-2.0%Si alloy is examined under large temperature gradients and fast freezing rate by using a new directional solidification apparatus. Temperature gradients were 55-145°C/cm and freezing rate was 3.3×10-3-7.0×10-2cm/sec. The dendrite arm spacing of primary austenite becomes gradually narrower by an increase in temperature gradient. Compared to the result obtained on a different specimen by the dynamic method with the same freezing rate, primary dendrite arm spacing of this study is smaller although secondary dendrite arm spacing is nearly equal. Critical cooling rate between stable and meta-stable eutectic solidification is 0.6°C/sec. When graphite-austenite eutectic colony solidifies in the transitional condition between meta-stable to stable eutectic solidification, it is proposed that the growth rate of the eutectic interface becomes discontinuous due to nucleation and growth of eutectic colony in liquid surrounded by austenite dendrite in front of the solid-liquid interface. It is also proposed that these growth of eutectic colonies have an effect on secondary dendrite arm spacing.抄録全体を表示PDF形式でダウンロード (765K) -
田中 雄一, 井川 克也1976 年 48 巻 11 号 p. 700-705
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーFine ferrite-pearlite duplex structures can be created in a variety of spheroidal graphite cast iron by a newly developed thermal treating process. The excepted improvement in tensile properties such as yield strength, tensile strength and elongation by matrix grain refinement has been observed in spheroidal graphite cast iron with fine duplex structure. In this study, the relation between toughness and matrix structures were experimentally investigated in the temperature range from -196°C to 200°C by Charpy impact test. When the matrix structure is a fine ferrite-pearlite duplex structure, it tends to improve the upper shelf energy level and lower the transition temperature when compared with the pearlitic one, where the tensile strength is nearly equal in both matrix structures. This tendency is especially remarkable in unnotched specimens which absorb a lot of energy before the initiation of cracks. The energy absorbed in the transition temperature range decreases according to the amount of segregation of non-metallic inclusions and undissolved cementite in the vicinity of the eutectic cell boundaries. But specimens with grains as small as several microns throughout the matrix shows a lowering of the transition temperature.抄録全体を表示PDF形式でダウンロード (847K) -
松原 安宏, 大城 桂作, 松田 公扶1976 年 48 巻 11 号 p. 706-711
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーDespite the fact that high chromium cast irons have been generally used as an abrasion resistant material because of their extreme hardness, systematic studies on solidification structures of high chromium cast irons are quite limited and several doubtful points remain on the iron-chromium-carbon diagrams. As a starting point to review certain areas of the iron-chromium-carbon diagrams reported in the past, primary and eutectic carbides were identified. Then the solidification processes of the cast irons were investigated by quenching method, and lastly the morphologies of the eutectic were determined by using a unidirectional solidification method. Hypo-eutectic, eutectic and hyper-eutectic high chromium cast irons containing about 10 to 40%Cr were prepared. The cast irons containing around 10 to 40%Cr were found to solidify under Jackson's diagram, because the primary and eutectic carbides were almost all M7C3 except M3C in 10%Cr irons. In hypo-eutectic irons, the eutectic nucleated in the liquid independent of the primary crystallites, and grew with a cellular interface. On the other hand, the eutectic of hyper-eutectic irons grew from the periphery of the primary carbides. In hypo-eutectic and eutectic irons, the eutectic that solidified as a colony structure consisted of matrix, fine rod-like carbides in the center, plate-like ones growing towards the colony boundary and coarse rod-like ones at the colony boundary. In hyper-eutectic irons, the eutectic showed the same structures as those of hypo-eutectic and eutectic irons, except when there was a big primary carbide in the center of the colony. The eutectic colony became fine as the carbon content was reduced, and it was finest at 30%Cr irons. The plate-like carbides changed into rod-like ones by increasing the chromium content.抄録全体を表示PDF形式でダウンロード (991K) -
高橋 恒夫, 神尾 彰彦, 手塚 裕康1976 年 48 巻 11 号 p. 712-717
発行日: 1976/11/25
公開日: 2012/09/13
ジャーナル フリーThe formation of primary alpha solid in hypo-eutectic Al-Si alloys was completed before approximately 20°C below liquidus temperature at cooling rates of 10 and 50°C/min. Sodium in the alloys accelerated the generation of primary alpha solid. Primary, secondary and ternary dendrite arm spacings exponentially increased with increasing local solidification time and decreasing cooling rate. Each dendrite arm spacing decreased with sodium, and dendrites were more chunky in a Na-containing alloy.抄録全体を表示PDF形式でダウンロード (763K)
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