| Budget Amount *help |
¥10,540,000 (Direct Cost: ¥10,300,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2004: ¥5,800,000 (Direct Cost: ¥5,800,000)
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| Research Abstract |
In this study, to establish a laser welding method for castings of different types of metal, laser irradiation of dental alloys was performed under various conditions to measure the penetration depth, tensile strength, and deformation, and the tensile break surface was observed for evaluation. Dental alloys used were titanium, gold alloy, high-gold ceramic bonding alloy, silver-palladium-gold alloy, and cobalt-chromium alloy. As a result, the penetration depth markedly differed among alloy types and under laser irradiation conditions. When laser irradiation energy was too strong, alloys scattered and hole within them, causing welding defects. Therefore, to perform laser welding, it was considered necessary to produce data bases regarding the relationships between laser irradiation conditions and the penetration depth and melting diameter of welding alloys. Furthermore, to obtain a stable laser beam, the irradiation energy of laser welding machines should be regularly measured and adjusted. On the other hand, alloy surface characteristics and defocusing influence the penetration depth and melting diameter. Furthermore, during laser welding, it is important to exclude oxygen using an argon gas shield. When the flow rate of argon gas is low, influences such as the oxidation of alloy occur. When strong laser irradiation penetrates alloys in dental plaster models, plaster components are evaporated and scattered, and alloys become brittle. The level of deformation of alloys differed under laser irradiation conditions. Deformation can be decreased by establishing appropriate levels for these conditions. From these study results, laser welding of castings of different types of metal was possible by closely adhering the junction areas at the welding site, and performing laser irradiation at the lowest energy level required to weld, creating conditions causing no welding defects.
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