熔融マグネシウム及びその合金の流動性に就て

抄録

A new apparatus for measuring the running quality of molten metals and alloyi has been designed by the authors. This apparatus consists of three parts; a metallic mould having a straight measuring canal about 150cm long whose cross section is an inverted equilateral triangle a side of which is 7mm, a sand mould of an inverted circular cone type which acts as a reservoir for the molten metal and a metallic mould having a downgate and a runner which leads to the measuring canal and acting as a part connecting the sand mould reservoir and the measuring canal.
To equalize the statical head of the molten charge throughout the test, a stopper is used in the sand mould. After filling the sand mould with the molten charge, this is removed and the charge is poured into the test mould. Assuming that the metal completely fills the measuring canal, the height difference in the reservoir is only about 2mm. The measuring canal is made by assembling two steel angles and one flat steel, and are coated with very fine alundum cement on their inner surfaces to prevent the metal from flowing in spherical drops because of extreme smoothness of the inner surfaces. The temperature of the mould is measured by inserting mercury thermometers into holes in the moulds, which are maintained at 70°. The pouring temperature is measured by an alumel-chrotnel thermocouple placed in the steel protecting tube.
By using this apparatus, the running quality of pure magnesium and the influence of a limited content of aluminium, zinc, manganese or copper on magnesium, and also the running quality of four kinds of industrial magnesium alloy, Elektron are studied. The results obtained are as follows:
The running quality of pure magnesium decreases by an addition of 5% aluminium, but increases by 10% addition The increasing effect of 30% aluminium is very marked. Zinc up to 2% gradually decreases the running quality of pure magnesium, but no further decrease is observable between 2% and 3%. A small amount of manganese within the extent added to the industrial magnesium alloy has no influence. An addition of copper up to 0.5 % gradually decreases the running quality of pure magnesium, but 1% copper suddenly decreases it. These phenomena should be attributed to many factors, such as casting conditions and inherent properties of alloying elements and others, but should be explained by the solidification theory and the equilibrium diagram as follows: the running quality of magnesium gradually decreases as an alloying element dissolves in magnesium and consequently the solidification range increases, showing a minimum value at the composition of a saturated solid solution and then gradually increases as the solidification range decreases, showing a maximum value at a composition corresponding to a eutectic, an intermetallic compound or others which have a constant temperature of solidification as does a pure metal, but as the equilibrium condition practically does not exist, the effect of supercooling and crystal segregation should be taken into account in considering the experimental results.