鋳鉄の流動性と溶解条件との関連
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概要
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Molten iron cast into a mold retains fluidity for a short time after commencement of solidification. Fluidity of completely liquified cast iron is regarded as the inverse of viscosity and since the viscosity of molten cast iron is extremely low it will not be very much affected by melting conditions. The fluidity of iron during solidification, on the contrary, will greatly be affected with the growth process of primary crystals since the iron flows together with these primary crystals. The authors considered that the growth process is charged by melting conditions, and thus assumed that the fluidity of iron during solidification would also be changed by melting conditions. Experiments were performed to confirm this assumption. The mold used for the fluidity test had a horizontal path of 15mm in diameter and 260mm in length with one end open. The molten iron was poured into the mold through a vertical sprue of 110mm in height and flowed out from the open end of the horizontal path. When the iron is poured at temperatures near the liquidus line solidification proceeds and the flow-out ceases. The fluidity of iron during solidification was investigated by measuring differences in the amount of flow-out and the flow-out rate of iron with a small variation in the pouring temperature near the liquid us line. Four irons with 3.52, 3.75, 3.95 and 4.49C.E. were selected as test materials, and were melted with three different melting conditions such as normal melting, oxidizing melting (0.5%Fe3O4 added) and inoculated melting (0.5%Ca-Si added). When the liquidus temperatures were determined, specimens of iron mixed with primary crystals were extracted at various temperatures below liquidus line with silica tubes, quenched into water and the shape of primary crystals at each temperature was obtserved microscopically. Fluidities obtained by experiment with various melting conditions are summarized as follows : 1) Fluidity increased with increasing C.E-value. This tendency was especially clear in normal melting. The fluidity of the normally melted iron was at the best when C.E.-value was more than 3.75. 2) The fluidity of the oxidized iron was worst when C.E.-value was more than 3.75, but when C.E-value was 3.52 the fluidity of normal iron was worse than that of oxidized iron. 3) The fluidity of inoculated iron was different from those of oxidized and mormal irons. The flow-out period was very long although its flow-out rate was low, and the flow-out rate became even lower with progressive solidification. These fluidity characteristics corresponded well with the behaviours of primary crystallization observed microscopically. Coarse and irregular formation of dendrites appeared in the oxidized iron and regularly branched fine dendrites were seen in the inoculated iron. It was considered that the above fluidity characteristics were affected by the dendrite formations.
- 日本鋳造工学会の論文
日本鋳造工学会 | 論文
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