Gases on various levels of cupola stack were taken through the wall and determined with a mass spectrometer. On the bases of the determinations the reaction of moisture in blast with coke and the oxidizing and reducing reactions of metals were discussed. At the later discussion, the variation of total oxygen in gases; To₂ calculated from the following equation were remarked.
    To₂={(O₂%)+(CO₂%)+1/(2) (CO%)}×78.1/(N₂%)×{100−(H₂O%)}+1/(2)(H₂O%)
  where; (    %) represents the determined value of each gas, and (H₂O%) represents the calculated value from (H₂%) and humidity of blast.
  On the behaviour of moisture in blast, it was revealed that while the moisture reacted with incandescent coke generating H₂ and CO₂ on the levels of 0 to 550 mm above tuyeres, a part of the H₂ gas on the higher level of the cupola turned into H₂O owing to the reaction with CO₂.
  By investigating the distribution of To₂ in cupola, it was clarified that the To₂ decreased on the levels of 0 to 350 mm above tuyere because of the oxidation of molten iron. On the levels of 550 to 750 mm above tuyere, however, the increase of the To₂ was recognized. In this zone the iron began to melt and its contact area with coke increased considerably, so that FeO on the surface of iron were reduced with coke. Moreover, in the preheating zone the decrease of To₂ appears which introduce by the oxidation of solid iron.

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  Behavior of charged materials descending in cupola have been chased with the use of γ-ray level meter. The measurement of bulk density and the thickness of each charged layer in cupola was able to perform by the γ-ray penetration method. As the charged metals and coke were mixed during descending in cupola in general, the bulk density of coke layer increased by mixing some metals into coke layer. The behavior of the charged materials descending in cupola were clarified by investigating these phenomena.
  The metals and coke are usually charged into cupola layer by layer separately, but it is inevitable that these materials are mixed at the boundary between both layers as they descend in the cupola. It was confirmed that if this type of mixing proceeded so much when they arrived melting zone, the level of melting zone was lowered. Subsequently tapping temperature was lowered and fractuation of iron quality was increased. When the coke size was smaller compared with charge metal size, both layers was more apt to be mixed. Therefore, it is important to avoid the mixing by selecting optimun sizes of metal and coke. The best cupola operation was obtained when the thickness of coke layer was about three times of the coke size which was one sixth of cupola diameter in normal.

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  In this investigation, blast temperature of cupola was varied systematically with use of two kinds of coke, differed in apparent specific gravity and ash content, corresponding to each supposed optimum cupola operating conditions. The effects of the blast temperature and coke on operating conditions of cupola and also on the properties of melt were investigated basically. It was summarized from the results obtained that as the blast temperature was raised melting and carburizing rate were increased, silicon and metal loss were decreased, and tapping temperature was raised.
  The higher the blast temperature raised, the more the properties of melt were depended on cupola melting conditions. Simultaneously the effect of coke on the melting condition, however, was decreased. For preheating the blast, externally fired hot blast system using towngas as fuel with heat exchanger was utilized.
  From the stand point of heat balance this externally fired hot blast system had been found sufficiently to be paid economically in cupola operation.

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  This study was carried out to estimate a practical application of the new equipment of oxygen enrichment which increased the heat efficiency of the cupola. This equipment is installed, with a automatic oxygen flow regulator, a pressure regulator and an oxygen injection part. The enrichment of oxygen in cupola blast is performed by direct injection of oxygen into main blast pipe by using automatic flow regulator.
  The water cooled, hot blasted cupola used for this study has a diameter of 480 mm, and an effective height of 3,050 mm. The charge metals were consisted of pig iron and steel scrap of which weight ratio was 1 : 1. The coke ratio was 10% in case of hot blast operation at 350°C, and was 14% in case of cold blast. Blast volume was 16.5 m³/min and 18 m³/min.
  The rate of enriched oxygen to blast air volume was 0.3% in case of continuous oxygen enrichment. However, in the intermittent oxygen enrichment in case of cold blast operation, the rate was from 0.5% to 1%.
  This experimental work covered the practical problem in cupola operation, the influence of oxygen enrichment on the chemical composition of molten iron and mechanical properties. Experimental results are summarized as follows.
  1. The raising the temperature of molten iron by continuous oxygen enrichment in hot blast operation was noticeably increased than in case of cold blast. This is probably by better combustion of coke which promoted by enrichment of oxygen in blast. Therefore, the possibility of reduction of coke ratio was recognized by this method. Oxygen enrichment when used intermittently increased the tapping temperature about 25°C than in normal operation.
  2. The influence of oxygen enrichment on the melting condition was a little without in the case of iron temperature, and had no trouble in the operation. However, an attention not to decreasing the height of coke bed is necessary.
  3. The influence of oxygen enrichment on the chemical composition of molten iron was not so large. Moreover, variation of mechanical properties or microstructures were not recognized by oxygen enrichment in blast.
  4. The authors are expecting to apply the results obtained in this study for commercial cupola operation more economically. Also it has been clarified that the reliability of this equipment was very large.

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  This experimental work was carried out in expecting to reduce coke ratio and to increase melting rate by using oil firing on the cupola operation.
  The cupola was used for this experiment, 300 mm inside diameter at tuyere, had two vertical type combustion chambers on both sides of the shaft. And combustion gas was blown through the lower part of the chambers which are located in 470-790 mm upside of tuyere's level.
  The favourable results in the cupola operation were obtained by 8-10% coke ratio and 20-35 1/t oil consumption ratio. By utilizing oil firing to cupola operation increasing of melting rate up to 20-40% was achieved and coke ratio reduced by 30-40% to compare with ordinary operation.
  Marked increasing of both CO₂ content in cupola exhaust gas and FeO content in slag were not obtained by oil firing. It was recognized, however, that H₂ content in exhaust gas reached to about 10%, whilst no special abnormalities were observed on the quality of molten iron.

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  The effects of raw materials, melting condition and composition of the iron melted in line frequency furnace on its solidification characteristics and casting properties were investigated by using statistical method, in an intention to find the critical factors in controlling of melting operation.
  The results were as follows.
(1) Quick analysis of composition before casting: The composition can be estimated accurately by measuring the solidification temperature range (ΔT) in thermal analysis. The relation between solidification temperature range and composition can be expressed by following equation.
          %C − 1/(6.4)%Si=3.985−0.00664·ΔT
  By chilling test also the carbon equivalent can be estimated, but only roughly. The strengh, however, can not be estimated by either thermal analysis or chilling test.
(2) Control factors: Control of element such as carbon or silicon, must be done more severely than in cupola operation. The effects of these elements on the characteristics of line frequency furnace melt is stronger than on cupola melt.
  Tensile strength was determined by carbon content and amount of steel scrap (SS%) in charge as shown in following equation.
          T.S.kg/mm²=76.26-16.44%C-0.394SS%
Consequently it is important to control the weight of steel scrap in charge as well as carbon content to obtain the constant strengh.
(3) Line frequency furnace iron v.s. cupola iron: If both iron had been melted from the same charge and had the same composition, chilling and shrinkage tendency were stronger in line frequency furnace iron than in the other. The tensile strength of the iron melted in line frequency furnace was higher by about 7 to 8 kg/mm² than the iron from cupola.
  It was found that eutectic temperature of line frequency furnace iron showed about 10°C lower than cupola melted iron, but showed higher nitrogen content. These facts were considered to be a cause of difference in many characteristics between both iron melts.

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  Experimental results on the melting procedure of cast iron by the use of heavy oil fired rotary furnace of 3 ton capacity have been summarized in this report. Experiments were made on the method of composition control, variation of chemical compositions during melting, variation of iron temperature with time elapsed and also on the quality and castability of iron obtained. Experimental results were in brief as follows:
  1) The carburization method by adding electrode scrap combined with 15 percent water-glass to half melted mushy iron was superior to other methods.
  2) Yields of silicon and manganese were better when they were added to iron at around 1,400°C than in case of adding them with original charging materials.
  3) Oxidation losses of carbon and silicon were large until iron temperature reached 1,400°C, while at temperatures higher than this, the reduction of both elements ceased and they became stable.
  4) Charged metals melted down in about 80 minutes after firing the burner and reached 1,470 to 1,500°C in 70 to 80 minutes thereafter. Those melting periods increased somewhat when furnace wall became thin after the many times of use or when slag volume was large.
  5) The mechanical properties of test castings were almost the same or rather better than those of cupola melting. The castability was good when the charging ratio of pig iron was high, but it was the same to that of cupola iron when the charging ratio of pig iron was only 10 percent.

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