冷却速率对高铬铸铁初生奥氏体稳定性的影响

Effects of cooling rate on stability of primary austenite of high chromium cast iron

借助金相显微镜、扫描电镜分析能谱,显微硬度仪,通过改变高铬铸铁(Cr15)凝固冷却速率,研究冷速对初生奥氏体稳定性的影响。结果表明:随着冷却速率增加,共晶组织含量先增加后减少,初生奥氏体量呈先减少后增加的趋势演变;初生奥氏体中固溶的C、Cr含量增加,奥氏体的过饱和度增大,当二次碳化物未析出时,初生奥氏体稳定性增加,一旦二次碳化物析出,其稳定性降低;初生奥氏体向马氏体转变数量减少,稳定性增强;共晶奥氏体和初生奥氏体边缘部位不稳定,最先发生A→M转变。

The effect of cooling conditions on the stability of primary austenite was investigated through changing the cooling rate of high chromium cast iron containing 15% Cr by means of optical microscope, scanning electron microscopy （SEM） and micro- hardness tester. The results show that the volume fraction of eutectic microstructure in increases first and then decreases with the increase of cooling rate, the volume fraction of primary austenite is on the contrary. The solubility of carbon and chromium atoms in primary austenite increases, so the supersaturation of austenite increases, the stability of primary austenite increases when no secondary carbides precipitate, however, once the secondary carbide precipitates, the stability of primary austenite decreases. The transformation quantity from primary austenite into martensite decreases, so the stability increases. The edge place between eutectic austenite and primary austenite is unstable, where the transformation from austenite into martensite first takes place.