CO2和H2O气氛下Fe-C合金薄带脱碳对比

 为了对CO₂和H₂O两种气氛的脱碳效果进行对比,将碳质量分数约为4.2%的Fe-C合金薄带分别在两种气氛中进行脱碳处理。通过热力学分析结合试验保证碳被脱除且铁不氧化的气氛条件分别为:Ar-CO-CO₂(气体流量为850 mL/min,CO的体积分数为25%,$P_{CO_2}$/(P_CO+$P_{CO_2}$)为0.26),Ar-H₂-H₂O(气体流量为500 mL/min,H₂体积分数为15%,水浴温度为313 K)。当脱碳温度为1 413 K时,Ar-H₂-H₂O气氛下,脱碳时间为50 min时,脱碳后的平均碳质量分数为0.6%,Ar-CO-CO₂气氛下,脱碳时间为70 min时,脱碳后的平均碳质量分数为0.92%。当脱碳时间相同时,Ar-H₂-H₂O的脱碳效果优于Ar-CO-CO₂的脱碳效果,由于随着脱碳反应的进行薄带表面与氧化气体反应达到平衡,Ar-H₂-H₂O反应平衡时薄带的碳活度要低于Ar-CO-CO₂气氛条件的碳活度,导致Ar-H₂-H₂O气氛条件下薄带的碳浓度梯度高于Ar-CO-CO₂气氛条件,进而导致Ar-H₂-H₂O气氛条件的扩散通量大,脱碳效果好。

Comparison of decarburization of Fe-C alloy strips in CO2 and H2O atmosphere

In order to investigate the decarburization behaviour of Fe-C alloy in CO₂and H₂O, the Fe-C alloy strips with a carbon content of about 4.2% were decarburized in Ar-CO-CO₂and Ar-H₂-H₂O atmospheres respectively. The atmospheric conditions that ensure the strips can be decarburized but iron not be oxidized were made by combining thermodynamic analysis and tests. The atmospheric conditions of the Ar-CO-CO₂ atmosphere were gas flow rate of 850 mL/min, mass percent of CO of 25%, $P_{CO_2}$/(P_CO+$P_{CO_2}$) = 0.26. The atmospheric conditions of the Ar-H₂-H₂O were gas flow rate of 500 mL/min, mass percent of H₂ of 15%, water bath temperature of 313 K. The average mass percent of carbon was 0.6% after 50 min at 1 413 K in Ar-H₂-H₂O. The average mass percent of carbon was 0.92% after 70 min at 1 413 K in Ar-CO-CO₂. The decarburization effect of Ar-H₂-H₂O was better than that of Ar-CO-CO₂ at the same decarburization time and temperature. The reason is that the carbon activity of the strips in Ar-H₂-H₂O is lower than that of the Ar-CO-CO₂ atmosphere when the decarburization reaction is in equilibrium. As a result, the carbon concentration gradient of Fe-C alloy strips in Ar-H₂-H₂O is higher than Ar-CO-CO₂. And the diffusion flux in Ar-H₂-H₂O is higher than Ar-CO-CO₂.