研究論文
凍結鋳物砂の特性とその凍結挙動について
1972 年 44 巻 11 号 p. 985-992
詳細
1972 年 44 巻 11 号 p. 985-992
Results obtained from the questionaire sent to the foundry shops in Hokkaido concerning the freezing of molding sand confirmed that there was great interest in this problem. This problem was little considered in the past and scientific research is very limited. On the realization of this fact the author began to study this subject from about two years ago. And some fundamental experiments have been carried out to obtain the characteristics and freezing behavior of frozen sand. In this report, the mechanical properties and permeability of frozen sand were compared with those of natural sand, and temperature change during cooling and deformity under freezing temperature were analyzed. From the experiments, interesting and important results were obtained which indicated that the characteristics of frozen sand should be positively utilized for casting mold in the future.
The outline of results is as follows:
(1) It is generally thought that frozen sand is inadhesive but the adhesion increases by a number of strong bridges of sintered ice as a final result.
(2) Mechanical properties of frozen sand with suitable moisture are not always inferior to those of natural sand, and increasing the moisture of frozen sand after ramming tends to remarkably improve the properties.
(3) Frozen sand before ramming is superior in permeability to natural sand, but frozen sand after ramming with increased moisture becomes inferior as the vents are filled with ice.
(4) A flat part is recognized on the cooling curve which shows the growth of ice layer. The length of this part becomes longer according to the increase of moisture and it changes with the composition of molding sand.
(5) An interesting behavior is observed in the deformation of frozen sand, which is the result of expansion and contraction. The mechanism of this deformation is almost similar to that of heated sand. The deformity of frozen sand is decided by the interaction of the expanding ice layer and the remaining constituents contracting by freezing.
