高溫預氧化對鑄鐵耐鋁熱熔損之作用

Effect of Pre-oxidation at High-temperature on the Thermal Erosion of Cast Iron in Molten Aluminum

本研究使用FC 250鑄造片狀石墨鑄鐵及FCD 450鑄造球狀石墨鑄鐵之商用鑄鐵為底材，實施750、850及900℃之高溫預氧化處理後，進行700℃的試片靜態和動態旋轉之商用壓鑄鋁矽合金（ADC12）熱熔損試驗。實驗結果顯示，鑄鐵之氧化層若具有良好的完整性及附著性，可阻礙鋁鐵之交互擴散，進而提升耐熱熔損能力。片狀石墨在高溫氧化處理時，氧化並形成連續的孔隙，提供氧氣滲入之路徑，使得氧化物沿片狀石墨晶界向材料內部快速生長，形成鋁矽熱熔損之阻礙層，因而相對於球狀石墨鑄鐵有較佳的耐鋁矽熱熔損之能力。

This study uses commercialized cast iron materials such as FC 250 flake graphite cast iron and FCD 450 spheroidal graphite cast iron as the substrate; then pre-oxidized at 750 ℃, 850 ℃ and 900 ℃ to obtain the surface scales. The static and dynamic thermal erosion tests were performed on oxidized specimen in order to investigate the effect of the oxide layer of the cast irons on the resistance of the thermal erosion in the molten Al-Si-Cu alloy (ADC12) at 700 ℃. The results show that the completeness and adhesion properties of the scales are the important factors that would influence the resistance to the thermal erosion. Since the flake graphite formed interconnected cavities after high temperature oxidized, the suitable sites for the oxide growth, the iron oxide grew faster and penetrated along the flake graphite's boundaries resulting in effective resistance to thermal erosion of ADC12. Therefore, the flake graphite cast iron has greater thermal erosion resistivity than the spheroidal graphite cast iron.