氧化对蠕墨铸铁导热性能影响的数值模拟

Numerical Simulation of the Effect of Oxidation on the Thermal Conductivity of Vermicular Graphite Cast Iron

服役条件下蠕墨铸铁的氧化导致其导热性能下降,进而恶化材料的服役环境。为准确评估蠕墨铸铁的服役寿命,文中采用扫描电镜观察蠕墨铸铁氧化后的微观组织形貌,借助氧化条件下蠕墨铸铁金相组织构建了蠕墨铸铁二维有限元导热模型,定量讨论了石墨和基体界面氧化层厚度δ对蠕墨铸铁的导热性能的影响。研究结果表明:当氧化层厚度约为6μm时,由于低导热氧化层的阻隔,基体的传热效率开始高于石墨;当氧化层厚度逐渐达到12μm时,蠕墨铸铁导热系数λ由无氧化状态的35.8W·m^-1·K^-1下降至26.7W·m^-1·K^-1,下降幅度高达25.4%。

The oxidation of vermicular graphite cast iron in service will lead to a decrease in its thermal conductivity,which will worsen its service environment.In order to accurately assess the service life of vermicular graphite cast iron,the VGI micro-morphology after high temperature oxidation was observed with a scanning electronic microscope.A two-dimensional finite element model for thermal conductivity was built on the metallographic microstructure of oxidized vermicular graphite cast iron.The effect of the thickness of oxide layer on the thermal conductivity of vermicular graphite cast iron was quantitatively analyzed.The results show that the heat transfer efficiency of the matrix is higher than that of graphite due to the barrier of the low thermal conductive oxide layer when the oxide layer is nearly 6 μm in thickness.When the thickness reaches 12 μm gradually,the thermal conductivity of vermicular graphite cast iron decreases from 35.8 W·m^-1 ·K^-1 to 26.7 W·m ^-1 ·K^-1,by as much as 25.4%.