Strain Development in Oxide Scale during Phase Transformation of FeO

Tanei, Hiroshi; Kondo, Yasumitsu

doi:10.2355/isijinternational.isijint-2016-552

Cited by 13 publications

(8 citation statements)

References 18 publications

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“…[12][13][14][15] Therefore, the research of phase transformation behavior of FeO in oxide scale has become a hotspot in recent years. [16][17][18][19][20][21][22][23] Based on the previous studies, it is worth noting that the chemical composition of steel also affects the phase transformation of FeO besides start cooling temperature, isothermal time and cooling rate. Shizukawa and Yoneda 21,24) proposed the effect of Mn, Au addition to steel on eutectoid transformation of FeO in oxide scale.…”

Section: Introductionmentioning

confidence: 99%

Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling

Cao

Lin

et al. 2018

ISIJ International

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Pre-oxidation in air at 750°C for 10 min, the plain carbon steels without Cr and containing 0.4 wt.% Cr tended to rapidly form oxide scale composed of outer Fe 3 O 4 layer and inner FeO layer. Moreover, a FeCr 2 O 4 layer was observed at the FeO/substrate interface on the steel containing Cr. A comparative study was carried out between the scales on the two steels in inert gas cooled from 350-600°C to room temperature at the cooling rate range of 1-40°C/min, to determine the effect of low concentration Cr addition on the phase transformation of FeO. Based on the cross-sectional morphologies of oxide scale during various cooling conditions, the relationship between cooling rate and start cooling temperature were constructed, and the area fraction of eutectoid structure was analyzed. The result shows that the transformation rate and area fraction of eutectoid structure in oxide scale on steel containing Cr were greater than that on steel without Cr, and then the nucleation, growth and 100% transformation region of eutectoid structure in oxide scale on steel without Cr were delayed. This study proposed two mechanisms to discuss the experimental results. Firstly, the formation of FeCr 2 O 4 layer reduced the consumption of O, and then prevented short-range uphill diffusion of Fe from FeO to substrate. Secondly, combined with the lamellar spacing in eutectoid structure and the Fe-Cr-O equilibrium phase diagram, the Cr addition increased the formation temperature of FeO in oxide scale, which provided sufficient driving force for eutectoid transformation during continuous cooling.

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Section: Introductionmentioning

confidence: 99%

Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling

Cao

Lin

et al. 2018

ISIJ International

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“…However, discrepancies still exist between reported values for Fe 1 − x O scales because of the decomposition of Fe 1 − x O into Fe 3 O 4 and Fe during the experiment. Such decomposition of Fe 1 − x O occurs below 833 K, according to the phase diagram of Fe-O system 9) and studies by Tanei et al 10,11) The phase transformation of Fe 1 − x O increased the measured thermal diffusivity because iron, which is formed by the phase transformation, has thermal diffusivity much greater than that of Fe 1 − x O. The decomposition of Fe 1 − x O had affected to values measured by Taylor et al and Li et al To derive the thermal diffusivity of Fe 1 − x O below 833 K, Li et al 6,7) corrected the measured data based on volume ratio of existing phases in the post-experiment samples.…”

Section: Introductionmentioning

confidence: 72%

“…Since Fe 1 − x O is a kind of semiconductor with low electrical conductivity, 24) the heat is mainly conducted by a phonon, and the phonon thermal conductivity can be expressed by the following equation: Equation (10) indicates that temperature dependence of thermal diffusivity of Fe 1 − x O is affected by v s and l l . The value of v s approximately equals the speed of sound in solids, which is assumed to be independent of temperature.…”

Section: Temperature Dependence Of Thermal Diffusivitymentioning

confidence: 99%

Determination of Thermal Diffusivity and Its Temperature Dependence of Fe<sub>1−<i>x</i></sub>O Scale at High Temperature by Electrical-Optical Hybrid Pulse-Heating Method

et al. 2021

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Thermal diffusivity of Fe 1 − x O scale formed on iron sheets have been measured using an electricaloptical hybrid pulse-heating method, which can avoid decomposition of Fe 1 − x O scale even at elevated temperatures by executing the experiment rapidly. The samples were 50 μm-thick Fe 1 − x O scale, which had been obtained by oxidation of a 0.5 mm-thick iron coupon at 1 123 K in the air followed by sandblasting to remove the outer oxide layers of Fe 3 O 4 and Fe 2 O 3 . In the experiment, the sample was heated by a large current pulse supplied to the iron layer of the coupon, and the Fe 1 − x O scale was indirectly heated up to experimental temperature from room temperature within 0.2 s. The temperature was maintained at the experimental temperature, and the laser flash method was conducted to measure the effective thermal diffusivity of the coupon. The laser irradiation position was adjusted by two ceramics blocks to make the temperature profile better. The effective thermal diffusivity produced the value for Fe 1 − x O scale based on a three-layered analysis for the Fe 1 − x O/iron/Fe 1 − x O structure. Thermal diffusivities of Fe 1 − x O scale were around 4.8 × 10 − 7 m 2 s − 1 , and there can be seen no obvious temperature dependence from 600 K to 900 K. X-ray diffraction analysis confirmed that phase transformation did not occur in the Fe 1 − x O scales during the experiment and x value was calculalted to be 0.09. Non-stoichiometry is supposed to have a significant effect on thermal diffusivity of Fe 1 − x O scale and its temperature dependence in this research.

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“…That is, at high temperature, Cr 2 O 3 in the inner oxide layer reacted with O 2 to generate CrO 3 gas that was volatilized outward, generating holes. The reaction schematic diagram is shown in Figure 7, and the reaction formula can be found in Equation (6). Due to the partial failure of the inner oxide layer, the protective Cr 2 O 3 was reduced, and the presence of holes provided a favorable channel for the two-way diffusion of iron and oxygen ions, thereby reducing the proportion of Fe 2 O 3 in the iron oxide layer and accelerating the oxidation rate of steel.…”

Section: Oxidation Mechanism Of Fe-10cr Steel In Airmentioning

confidence: 99%

“…In order to reduce iron oxide scales production in the hot rolling process and improve the oxidation resistance of steel, research has been carried out on heating systems, rolling systems, and alloying elements [5][6][7][8]. It has been widely recognized that adding Cr element to steel can improve the oxidation resistance of steel.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Oxidation Behavior of Fe–10Cr Steel under Different Atmospheres

Liu

Sun

et al. 2021

Materials

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Using a thermogravimetric analyzer (TGA), Fe–10Cr steel was oxidized in dry air and in a mixed atmosphere of air and water vapor at a relative humidity of 50% and a temperature of 800–1200 °C for 1 h. The oxidation weight gain curves under the two atmospheres were drawn, the oxidation activation energy was calculated, and the phase and cross-sectional morphology of the iron oxide scales were analyzed and observed by X-ray diffractometry (XRD) and optical microscopy (OM). The results showed that when the oxidation temperature was 800 °C, the spheroidization of Fe–10Cr steel occurred, and the oxidation kinetics conformed to the linear law. At 900–1200 °C, the oxidation kinetics followed a linear law in the preliminary stage and a parabolic law in the middle and late stages. In an air atmosphere, when the oxidation temperature reached 1200 °C, Cr2O3 in the inner oxide layer was partially ruptured. In an atmosphere with a water vapor content of 50%, Cr2O3 at the interface reacted with H2O to generate volatile CrO2(OH)2, resulting in a large consumption of Cr at the interface. At the same time, a large number of voids and microcracks appeared in the iron oxide layer, which accelerated the entry of water molecules into the substrate, as well as the oxidation of Fe–10Cr steel, and caused the iron oxide scales to fall off. Due to the volatilization of Cr2O3 and the conversion from internal oxidation to external oxidation, the internal oxidation zone (IOZ) of Fe–10Cr steel under water vapor atmosphere decreased or even disappeared.

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Strain Development in Oxide Scale during Phase Transformation of FeO

Cited by 13 publications

References 18 publications

Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling

Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling

Determination of Thermal Diffusivity and Its Temperature Dependence of Fe<sub>1−<i>x</i></sub>O Scale at High Temperature by Electrical-Optical Hybrid Pulse-Heating Method

High-Temperature Oxidation Behavior of Fe–10Cr Steel under Different Atmospheres

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