金銀パラジウム合金の鋳造法の違いが諸性質に及ぼす影響
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概要
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Dental Au-Ag-Pd alloy is usually melted by a gas-air blow torch in air and cast with a centrifugal machine. In this study, the possibility of improving the characteristics of the alloy castings was investigated for some other casting methods. The casting machines used were Castmatic CM-230 (CM) : arc heating in Ar gas and suction-Ar gas pressure type ; Argoncaster-DX・S (AC) : induction heating in Ar gas and vacuum-Ar gas pressure type ; Caspac-MK3 (CP) : resistance heating in carbon crucible and vacuum-air pressure type ; and Sure CV-51 (SR) as a control : gas-air flame heating in air and centrifugal pressure type. The vacuum-pressure type machines, AC and CP, showed superior ability to cast the alloy into thinner detail. The ability was the worst in the suction-pressure type, CM. It may be atributed to its insufficient suction effect through the investment mold. The roughness value of the as-cast crown surface became the largest with AC and smallest with CP and SR. It was found from SEM observation and X-ray microanalysis that the roughness on AC casting was caused by dendritic structure with less oxide formation while the smoother surfaces on CP and SR castings were due to the thick oxide formed on the dendrite. There were more micro porosities and oxide inclusions in the casting with CM than those with the other machines probably because CM tended to cause overheating of the alloy and poor suction effect. Marked increase in pores was observed when the alloy was repeatedly cast with this machine. The presence of such pores and oxide inclusions were reflected in lower elongation of the castings with CM and SR in tensile test. The casting with CP having few pores and inclusions showed highest elongation. No significant differences in the dimensional change of the cast crown were found among the casting machines. It is summerized from these results that the castings with AC and CP at mold temperature of 700℃ were superior in several important characteristics to those with CM and SR. Although CM has some advantages such as ease of manipulation and short-time completion of the casting process, it may be necessary to improve its suction effect for producing better castings.
- 九州歯科学会の論文
- 1988-12-25