鑄物砂の耐久度並に燒附に關する研究

鑄物砂の研究 第4報

抄録

The most important properties of moulding sands in reference to the refractoriness are the so=called "durability" and "burning on". In this report, the experiments by casting for the moulding sands of Japan and Manchuria were conducted in the same conditions as in foundry as far as possible, and after it, the used sands and the surfaces of casting were investigated from the points of view of the durability and the burning-on.
Comparing the results with the properties of bonding materials of moulding sands related in the 3rd report, the following conclusions were obtained.
(1) One of the most important properties of moulding sands influencing the durability is the quality and the quantity of bonding materials, e.g. the durability of moulding sands depends chiefly upon the reversibility of the water of kaolin and the irreversibility of the water of ferric hydrogel after heatihg at 400°C. Therefore, the durability of moulding sands which depends mostky upon the latter for its bonding power is comparatively weak.
(2) The durability of moulding sands depending mostly upon the quality and quantity of bonding material, the water-vaporization-experiments by the thermo-balance by prof. K. Honda are the most suitable methods for the durability test of moulding sands.
(3) For the burning-on, the most influential factor of moulding sands is the mineral composition of sand grades: The feldspar group of lower melting point is undesirable, especially orthoclase is detrimental. The naturally bonded moulding sands of Japan and Manchuria contain comparatively large quantity of the feldspar group.
(4) In order to protect from the burning-on, it is necessary conditions for bonding part that after casting, the bond near at the caked metal fuses in glasssy state, incloses sand grains and thus makes the so-called "scale". In cooling, it parts easily from the surface of casting by the difference of coefficient of expansion.
(5) The same principle holds good in steel casting. If necessary to lower the melting point of the bonding material with the purpose of making the scale, the addition of powdered iron oxide to it is one of the effective methods to protect from the burning-on.