치과주조용 제 Ⅲ형 금합금의 열처리에 따른 경도 및 미세조직

Abstract

Since the dental casting principle has been applied to dental clinic, crown fabrication by casting alloy has been widely used to restore dental loss. The purpose of this study was to examine the change in hardness and microstructure of heat treatment specimens using home-made dental casting Ⅲ type gold alloy. To do this experiments, specimens were buried, casted, and done heat treatment under the same condition using DM-72. Then, the specimens were divided into five groups with two each of experiment. The following results were obtained. 1. The hardness number of cast specimens was 139.00±4.58. It was slightly higher(15.83%) than minimum hardness number of type Ⅲ gold alloy(120)(P＜0.05). 2. The hardness number of type Ⅲ gold alloy by heat treatment was generally higher. The specimen 10-minute aging treatment at 250℃ was found to be the highest in hardening rate(205.00±8.89). The formation of AuCu super-lattice or the precipitation of Ag-rich phase and Cu-rich phase might partially be contributed. 3. While heat treatment temperature became increased, the hardness number of specimens became higher, heat treatment time of 60 minutes is more decreased the hardness number. Heat treatment for 5 ~ 30 minutes generated satisfying hardness number. 4. The structure of casting condition was columnar dendrite-grown casting structure. The grain size of hardening heat treatment specimens were more smaller in structure and precipitation, while softening heat treatment ones were coarser in shape and size of grain. 5. The grain size of heat treatment specimens in a furnace casting and water quenching were more smaller in structure and as temperature and time became higher and longer, the shape and size of grain became coarser. In conclusion, heat treatment of dental casting type Ⅲ gold alloy showed higher hardness number than the cast specimens. Accordingly, heat treatment will improve the mechanical properties of type Ⅲ gold cast alloy used in this study.