生型合成砂用基本砂の研究（第1報）

— 搗固めによる變形について —

抄録

    Influences of grain size distribution and grain shape of moulding sand on its physical properties have not yet been fully discussed owing to the complexity of multiple combinations of the factors.
    In case of adopting a new type of synthetic moulding sand, however, every foundry has to face with the problems to discuss its grain size distribution and grain shape.
    That is, in view of mouldability and stability, they seem to be the fundamental problems for a mass production system.
    In this report, several data and experiences on silica sands for steel and malleable castings which are used in our foundry, are analised and discussed.
    Especially, changes of volume by ramming were measured and compared on three kinds of different base sands containing bentonite and moisture.
    These leading results obtained are as follows :
  (1) Volume or height of a sand specimen weighing 200 g, which is given a constant ramming energy, indicates its maximum value in a constant moisture content on the curve showing the relation between specimen height and moisture.
  (2) Over 2 blows with a standard rammer, there is a proportional relation between height or volume of a sand specimen and a logarithm of the number of ramming.
  (3) Provided |b| as the gradient of the line which has been calculated by the least square method and ‘a’ as the height of the sand mass which is given two times of blow, then the former expresses the deformability in ramming per a unit ramming energy and |b|/a expresses the compactability.
  (4) The more bentonite is added the higher the |b| is. Each sand indicates its maximum value in each constant moisture on the curve showing the relation between |b| and moisture.
    In this experiment, base sand Ⅲ having an optimum grain size distribution and a subangular grain shape showed the highest value of |b| among these three sands.
  (5) In view of Dietert's Flowability, base sand Ⅲ having the largest value of |b| is thought to be related to this flowability and has smallest value of flowability. This sand is, however, considerd to have a close value to Kyle's Flowability which usually indicates an important phase of mouldability.