It needs no explanation that cast iron plays an important role in the present mechanical industry, and, above all, to make the cast iron which has a high resistance against abrasion as well as good mechanical properties is highly desirable. The present experiment has been done in order to realize this end through the improvement of the melting method. The result of this experiment may be briefly summarized as follows:
(1) When composition of cast iron is same as that of a high grade cast iron;
(a) It is reasonable to consider that the property of cast iron varies as the kind of pig iron used, and that there is the so-called heredity in its property.
(b) The mechanical property can be improved by raising the casting temperature, but the degree of improvement is lessened if the melting temperature is raised.
(c) Raising the melting temperature generally improves its mechanical property.
(d) Examing the structure, it reveals that melting and casting at high temperatures result a satisfactory structure of the so-called “Kikume” or inter locking hook.
(2) When pig iron is used;
(a) In case of Kanaaisi No. 3 pig, the improvement of mechanical properties can not be expected by melting and casting at high temperatures. However, graghite is refined at a melting temperature of 1,500° and above, and becomes finer at casting temperatures ranging from 1,350° to 1,400°.
(b) In case of Honkeiko No. 1 high grade pig, mechanical properties can not be improved by melting and casting at high temperatures, and also the refinement of graghite is not so noticeable as in case of Kamaisi No. 3 pig.
(3) When a mixed pig is used;
(a) The melting and casting at high temperatures improve mechanical properties.
(b) The melting and casting at high temperatures graghite finer.
(4) When melting in the cupola;
(a) The melting at high temperatures with the cupola can be done by the hot blast system.
(b) The casting at high temperatures with the hot blast cupola gives good mechanical properties.
(c) Even with the hot blast cupola, at least 20% of reclaimed material is necessary to be added to the charge instead of the fresh pig only.
(d) The iron melted in the hot blast cupola shows very good structure, the graghite being finer.
(5) The foundation of designing the air heater for the hot blast cupola has been established.
(6) The salient features of the hot blast cupola:
(a) The temperature of molten metal is 80° higher than that by cold blast cupola.
(b) From the first tapping, the temperature of the molten metal is favourably high, and the fluctuation of the temperature throughout the operation is very little.
(c) The structure of the casting is superior and its mechanical properties are also better as compared with that by ordinary cupola.
(d) Any bad effect can hardly be noticed, even when air of high humidity is blown in.
(e) From 20% to 30% of coke consumption can be saved.
(f) Percentage of the failed casting can be reduced.
(g) The use of second grade coke is poSsible.
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