無機樹脂水玻璃砂之加熱乾燥強度

The Strength of the Inorganic Binder, Sodium Silicate, Sand by Heating and Drying

劉承勳(Chang-Yung Liu) ； 許富淵(Fu-Yuan Hsu)

《鑄造工程學刊》 46卷3期 (2020/09) Pp. 33-44

摘要

水玻璃砂不論是物理硬化和化學硬化皆為物理性的脫水機制，所以本實驗利用物理加熱的方式來使水玻璃砂模脫水硬化，藉由固定矽砂及水玻璃的成分比，利用添加額外的含水量，將水玻璃砂製成為長條型試棒，並且利用單方向加熱的方式達到水玻璃砂脫水乾燥。通過改變加熱時間和含水量的變化，來了解何者影響砂模較大，並利用自硬性樹脂砂來做對照。將不同的加熱乾燥時間和不同含水量的試棒，進行三點抗折的強度試驗，希望藉由不同含水量及乾燥時間得到水玻璃砂強度的變化。本實驗發現含水量和加熱時間只影響水玻璃砂模的熱定型高度，但並不影響砂模強度。和有機樹脂相比，強度約為有機樹脂的三分之一，可能是因為砂模體密度偏低，使試片強度過低。而2%含水量在加熱二十分鐘後強度突增但隨後弱化，推論係加熱過程的矽酸鈉的相變化所致。

關鍵字

水玻璃砂膜 ； 水玻璃物理硬化機制 ； 熱定型樹脂砂 ； 砂模強度

並列摘要

The hardening mechanism of sodium silicate sand mold is classified by the physical and chemical mechanism. However, various authors point out the main mechanism is the dehydration of sodium silicate (water glass) during the hardening process. In this study, the physical heating drying method to harden sodium silicate is utilized. It is one of purposes of this study to valid the dehydration theory. The test squared sand bar was made by a constant composition of sand and water glass with additional specific water portions. One directional heating from the bottom of test bar is applied to dry the mixture. Various drying time and water contents in the water glass sand mixture are tested to understand the main influence of the strength of the test bars. Additional resin bonded sand was also made to do comparison experiment with the water glass sand bars. The strength of sand test bars was examined by three point bend test. In the result, the drying height of sand test bar is influenced by the heating time and water content. However, the strength of the sand bar remained constant for all these tests. It is independent of the water content and drying time. In the low water content 2% in the mixture bar, its strength showed an abrupt change at 20 minutes of heating time. And after this time, the strength is declined again for heating. It is implied that the phase transformation of sodium silicate took place at this time of heating. Some other influences for the strength of sodium silicate sand is needed to further study.

並列關鍵字

Sodium silicate sand mold ； Physical sodium silicate hardening mechanism ； Thermo-setting resin sand ； Sand mold strength