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利用热重法研究了低碳钢在500~900℃恒温氧化动力学,利用扫描电镜和金相显微镜对氧化铁皮的表面和断面形貌进行了观察。在试验基础上建立了恒温氧化动力学模型,并推导变温条件下氧化动力学模型用于氧化铁皮厚度演变计算,并研究了氧化铁皮中三种铁的氧化物的生长方式。结果表明:数值模拟出的铁皮厚度与实测结果十分接近。这种模拟方法解决了轧制过程中,高温情况下无法直接测量氧化铁皮的厚度问题,为调整生产工艺参数、控制氧化铁皮厚度提供了参考。FeO的晶粒是以三角锥型或是金字塔型的生长方式。Fe3O4在氧化初期是以柱状晶的形式生长;而在氧化后期,Fe3O4的生长方式转变成大量的柱状晶和团簇状结构的复合组织。Fe2O3有金属须状、片层状和多边形晶粒状三种生长方式。金属须状的Fe2O3对氧化增重影响不大,但对Fe2O3层相对厚度增加。
The thermogravimetric method was used to study the isothermal oxidation kinetics of mild steel at 500-900 ℃. The surface and cross-sectional morphology of the scale were observed by scanning electron microscopy and metallographic microscope. Based on the experimental results, a constant temperature oxidation kinetics model was established and the oxidation kinetics model under varying temperature was used to calculate the thickness evolution of the scale. The growth patterns of three iron oxides in the scale were also studied. The results show that the numerical simulation of the thickness of the metal sheet is close to the measured result. The simulation method solves the problem that the thickness of the scale can not be directly measured during the rolling process under high temperature conditions, and provides a reference for adjusting the production process parameters and controlling the thickness of the scale. FeO grains are triangular pyramid or pyramid-based growth. In the early stage of oxidation, Fe3O4 grows in the form of columnar crystals. In the late stage of oxidation, the growth mode of Fe3O4 transforms into a large number of composite structures with columnar crystals and clusters. Fe2O3 metal whisker, lamellar and polygonal grain three kinds of growth. Metal whisker Fe2O3 has little effect on the weight gain, but the relative thickness of the Fe2O3 layer increases.