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Kinetics of iron oxidation with eater vapour at temperatures between 1300 and 1450 deg C

机译：在 1300 至 1450 摄氏度的温度下与食者蒸气氧化的动力学

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In this paper measurements of the kinetics of iron oxidation in H_2O-containing gas mixtures of various compositions in the temperature range of 1300 to 1450 deg C, and metallographic examinations are described. The reaction product is solid wustite below and liquid iron saturated iron oxide above 1377 deg C, this temperature being the incongruent melting temperature of iron saturated wustite. The experiments were carried out by measuring the weight increase during the oxidation of an iron specimen connected to a thermo-balance with a platinum wire. The water vapour was generated by means of a water vapour saturator. The rate law is linear in the beginning of the single experiment and later becomes parabolic. The linear law was interpreted as being caused by two resistances connected in series: the transport of the oxidising gas through the adjacent gas boundary layer, and the phase boundary reaction at the oxide interface. The parabolic law was interpreted as being determined by the transport of iron ions and vacancies through the growing oxide layer. The resistance of gas transport becomes negligible above a certain critical gas velocity which is, for example, 23 cm/s at 1342 deg C. The temperature-dependent values of the phase boundary reaction rate constant were calculated with the help of known theories from the results of those experiments in which the gas velocities were above the critical value for gas transport at the respective temperatures. The parabolic law did not apply, when the oxidation product was liquid as under these circumstances the formed oxide dropped off the specimen during the experiment and hence, became no thicker than 22 mu m. For all the experiments the oxide layer was composed of wustite, even when the oxygen potential of the reaction gas was far higher than that for equilibrium of the gas with wustite and magnetite. The surface structure of the oxide layer and the grain sizes varied with temperature. At lower temperatures the grains were relatively small while at higher temperatures they became extremely large up to a diameter of 6 mm.
机译：本文描述了在1300至1450°C的温度范围内，各种成分的含H_2O气体混合物中铁氧化动力学的测量，以及金相检查。反应产物为1377°C以下的固体乌氏石和液态铁饱和氧化铁，该温度为铁饱和乌氏铁的不一致熔化温度。这些实验是通过测量用铂丝连接到热天平的铁试样氧化过程中的重量增加来进行的。水蒸气是通过水蒸气饱和器产生的。速率定律在单个实验开始时是线性的，后来变成抛物线。线性定律被解释为由两个串联的电阻引起：氧化气体通过相邻气体边界层的传输，以及氧化物界面处的相边界反应。抛物线定律被解释为由铁离子和空位通过生长的氧化层的传输决定。气体输送的阻力在某个临界气体速度以上可以忽略不计，例如，在 1342 摄氏度时为 23 厘米/秒。相界反应速率常数的温度相关值是借助已知理论计算的，这些实验结果中的气体速度高于相应温度下气体传输的临界值。当氧化产物为液态时，抛物线定律不适用，因为在这种情况下，形成的氧化物在实验过程中从试样上脱落，因此厚度不超过 22 μ m。在所有实验中，氧化层均由乌氏石组成，即使反应气体的氧势远高于气体与乌氏石和磁铁矿平衡的氧势。氧化层的表面结构和晶粒尺寸随温度的变化而变化。在较低的温度下，颗粒相对较小，而在较高温度下，它们变得非常大，直径可达 6 毫米。

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