中碳域铁碳合金薄带气—固反应脱碳研究

Experimental of Gas-solid Decarbonization Process of Fe-C Alloy Ribbon in Medium Carbon Region

为了研究中碳域铁碳合金薄带固态下的脱碳规律,试验以初始碳质量分数1.2%、1.5 mm厚的铁碳合金薄带作为研究对象,以界面气—固反应的形式对薄带进行脱碳处理。通过调整入炉Ar-H2-H2O的流量比例,控制气氛PH2O/PH2为0.61。脱碳温度选用1 353、1 413、1 453 K,保温脱碳时间为10~40 min,间隔为10 min。研究表明:薄带的脱碳反应近似为表观一级反应,求解得到反应活化能为68.85 kJ/mol,脱碳过程的限制性环节为碳在薄带基体内的扩散。拟合得出试验条件下薄带剩余平均碳含量经验公式为wt=1.2e((0.148 82-1.28×10-4T)t)。提高脱碳温度既可有效提高脱碳速率又可增大极限脱碳量。随着脱碳处理时间的延长,碳的浓度梯度差减小、扩散行程加大,脱碳速率会逐渐降低并出现明显的转变节点。

In order to study the decarbonization development of iron-carbon alloy in carbon domain,an initial carbon fraction of 1.2% and 1.5 mm thick Fe-C alloy thin strip was used for this purpose.Decarbonization of the strip had been conducted in the form of interface gas-solid reaction.The PH2O/PH2 of the atmosphere in the furnace was controlled at 0.61 by adjusting the flow ratio Ar-H2-H2O.The experimental temperatures were set to 1 353 K,1 413 K and 1 453 K.And the decarburization time was set to 10~40 minutes.The results show that the decarbonization reaction of the strip is similar to that of the order reaction,and the activation energy is 68.85 kJ/mol.The limiting factor of the reaction is the diffusion of carbon in the thin strip.Tthe empirical formula for the average carbon content in the strip had been fitted and expressed as wt=1.2e((0.148 82-1.28×10-4T)t).Increasing the decarbonization temperature can not only increase the decarbonization rate but also increase the limit decarbonization amount.With the increase of decarbonization time,the gradient difference of carbon concentration decreases and the diffusion stroke increases.The rate of decarbonization decreases gradually and appears obvious nodes.