低周波電気炉球状黒鉛鋳鉄の逆チルと溶湯保持との関係について
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概要
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The first part of this article describes the prevention of inverse chill of spheroidal graphite cast iron melted by a 2 t coreless type low frequency furnace lined with SiO2 and treated by magnesium-rare earth mixtured spheroidal reagent (KC-reagent) in foundry works. The inverse chill often appeared in the case of the spheroidized treatment of molten irons which were not held at all or held above 70 minutes at 1,500°C, but it was eliminated by holding the moten iron about 13 to 60 minutes at 1,500°C. It was found that inverse chill was generally associated with low graphite nodule number and imperfect spheroidal graphite forms, and the lower the graphite number the stronger was the chilling tendency. In the second part of this article, the effect of holding molten irons for applicable frequency of lined material and change of Sc was investigated. The change of chemical compositions and the behavior of gas elements (nitrogen and oxygen) were as follows. In either case carbon slightly decreased, while silicon slightly increased, but manganese, phosphorous, sulpher, chromium and titanium did not change. However when the applicable frequency was great (70 times), titanium slightly increased. In spite of Sc value, the Ns (hydrochloric acid soluble nitrogen) content changed little, but when Sc was low, the Ns content was higher than the value when Sc was high. This phenomenon corresponded with the thermodynamic equilibrium value of Ns. In either case the NI (hydrochloric acid insoluble nitrogen) content slightly decreased, but only when the applicable frequency was great (70 times), the NI content slightly increased to be as much as titanium value. In the case of high Sc, oxygen was increased by holding ever 50 minutes. This increase of oxygen may have promoted the tendency of chill effect and undercooled graphite formation. In the case of low Sc, chilling depth changed little and undercooled graphite did not appear. Though oxygen content showed a tendency to increase, it was essentially little different with high Sc melts. In the last part of this article, the contents of gases in molten irons melted by cupola and low frequency furnace were compared. The Ns content was little different in both melting methods, but the NI content in cupola was a little higher than for the low frequency furnace. On the other hand, oxygend ontent in the case of cupola was almost twice as much as in the case of the low frequency furnace, but after spheroidizing treatment, it decreased remarkably to the oxygen content of spheroidized low frequency furnace melts.
- 日本鋳造工学会の論文
日本鋳造工学会 | 論文
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