铬元素添加对热轧低碳钢高温氧化行为的影响

Effects of chromium addition on high temperature oxidation behavior of hot rolled low carbon steel

为了研究铬元素和加热工艺参数(加热温度、保温时间)对热轧低碳钢表面氧化铁皮形成过程的复合作用,采用热重分析法研究了铬含量对低碳钢在1100~1250℃空气中氧化行为的影响规律,计算了氧化速率常数,并对比了不同试验条件下氧化铁皮的物相组成、显微结构以及微区元素占比。结果表明,所有氧化过程均呈现两阶段特征,即初期氧化动力学曲线呈线性规律,中后期逐渐转变成抛物线规律,而从线性到抛物线转变所需时间会随着钢中铬含量的升高而缩短;同时,铬元素添加后氧化铁皮的结构由最外侧的Fe_(2)O_(3)层、中间的Fe_(3)O_(4)层和FeO层以及靠近基体的富铬尖晶石(FeCr_(2)O_(4))层组成,FeCr_(2)O_(4)层在氧化过程中通过阻碍铁离子和电子的外扩散,降低了氧化速率,从而显著提高低碳钢的抗高温氧化性能。

In order to study the compound effect of chromium and heating process parameters(heating temperature,holding time)on the oxide scale formed on the surface of hot rolled low carbon steel,the effect of chromium content on high temperature oxidation behavior of low carbon steel in air at 1100-1250℃was studied by thermogravimetry analysis.The oxidation rate constant was calculated.The phase composition,the micro-structure and the element proportion of oxide scale under different experimental conditions were compared.The results show that the high temperature oxidation presented a two-stage model.The oxidation kinetics curve was linear in the early stage of oxidation,and then changed to parabolic in the middle and late stage of oxidation.The transformation time from linear to parabolic was shortened with the increase of chromium content in the steel.The structure of the oxide scale was composed of the outermost Fe_(2)O_(3)layer,the middle Fe_(3)O_(4)layer and FeO layer,and the chromium rich spinel(FeCr_(2)O_(4))layer near the substrate after the adding of the chromium.In the oxidation process,the FeCr_(2)O_(4)layer suppressed the outward diffusion of the iron ions and the electrons,and reduced the oxidation rate.Meanwhile,the high temperature oxidation resistance of low carbon steel was significantly improved.