This investigation was carried to obtain quick malleable cast iron by means of Magnesium treatment. Magnesium has the effect to convert cast iron into white and also favors the spheroidization of graphite.
  High silicon white cast irons, for example, which contain 3% carbon and 2% or more silicon, will be malleablized in very short time. However, irons of the above mentioned composition can not be used in ordinary malleable cast iron process. Because, they get flaky graphite structure, when they are cast in normal green sand mould. When they are treated with Magnesium, white cast irons or mottled irons, mixed with nodular graphite are obtained.
  In our experiments, these irons were annealed in short time ; for example, at 900°C∼950°C for few hours in the first stage and at 700°C. of the second stage for 5∼6 hours longer than the first stage.
  In these experiments, it was shown that the decomposition time of both free cementite and pearlite cementite was not prolonged by the Magnesium treatment.
  Microstructure of quick malleable cast irons after the Magnesium treatment, has nodular graphite and temper graphite, the form of which is either rounded or star-like.
  These quick malleable irons have such high strength and ductility, as 40∼50kg/mm² tensile strength and about 10% elongation.

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  Good selecting both in mixture of raw materials and drying method of a core gives us an oil sand core having better permeability efficiently. The characteristics of the oil sand core which dried in an electric resistance oven applicating hot blast circulating system were studied.
  It is obvious that this drying method is superior than normal drying methods using in many foundries.
  From our studies, it can be concluded that shown in followings.
  (a) Studying of oil sand can be divided two reactions, one is drying reaction and the other is decomposing reaction in high temperature. The difference of two types of drying oven, hot blast system and closed system, becomes to apparent.
  (b) Volume of evolved gases and their composition were examined by re-heating oil sand cores. Also the comparison of gases evolved in decomposing of oil in sand core both in hot blast and closed system were carried out.
  (c) The more the oil addition to oil sand, the larger the gas evolvement.
  (d) The effect of temperature on a decomposing reaction were also examined.
  (e) It seems that the better the permeability of sand, the easier the evolvement of gas in re-heating treatment. In other words, the exclusion of gases by re-heating from the oil sand core dried efficiently in our oven is very easy compared with the oil sand core dried in other oven. (N. T.)

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