Papers by Keyword: Oxide Scale

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Authors: Y.P. Jacob, V.A.C. Haanappel, Eric Caudron, Henri Buscail, M.F. Stroosnijder
Authors: Xiang Long Yu, Zheng Yi Jiang, Jing Wei Zhao, Dong Bin Wei, Ji Zhou
Abstract: In hot rolling, metal oxides formed on steel surface can generally be classified as primary, secondary and tertiary oxide scales, corresponding to the reheating stages, the roughing stages and the finishing passes of continuous mills, respectively. The tertiary oxide scale grows into the final products on the hot-rolled steel strip during the finishing rolling and the subsequent cooling down to ambient temperature. We provide here a systematic overview of the oxidation mechanism, microstructure and microtexture development of the tertiary oxide scale. Mechanism of oxidation and Fe3O4 precipitation in tertiary oxide has been given as the fundamental theory. Three main sections has been divided in this review. The first section includes experimental investigations on microstructure evolution from the formation of oxide scale during hot rolling, then through continuous cooling, to Fe3O4 precipitation behaviour in storage cooling of hot-coiled strip. By using electron backscatter diffraction (EBSD) to characterise both the steel substrate and the oxide scale concurrently, the second section has further dealed with the texture-based analysis of oxide scale: phase identification, orientation analysis and coincident site lattice (CSL) boundaries. The third section has provided the general type of crystallographic texture and its evolutions in deformed Fe3O4 and steel substrate. Finally, the upcoming challenges have been addressed in this intriguing and promising research field.
Authors: Colette O'Meara, J. Sjöberg
Authors: Ding Ping Liu, Zhi Hu Ai, Jian Chen Hu
Abstract: The paper addresses the assessment of the high-temperature oxidation behavior of T91 in supercritical boilers. The trend to higher steam temperatures and longer periods of full-load operation greatly increases the oxidation corrosion on the steam-side surface. The oxide films can lead to major failures and consequently to reduced plant availability. The exfoliation of the oxide scale may block the tubes somewhere in the system with the potential for causing tube explosion. The oxide scale of T91 was sampled and analyzed by the energy dispersive X-ray spectrometry (EDXS) and the X-ray diffractmeter (XRD). The mechanism of oxidation corrosion and scale exfoliation, as well as its influence factor, were described. The measures were brought forward so as to provide a scientific guidance for dealing with oxidation corrosion and oxide exfoliation on a large scale in T91 in the supercritical boiler.
Authors: Zheng Yi Jiang, Jian Ning Tang, A. Kiet Tieu, Wei Hua Sun, Dong Bin Wei
Abstract: In this paper, the effects of the surface asperity wavelength, reduction and lubrication (friction) on the surface roughness transformation of the oxide scale have been studied. The simulation results show that the oxide scale surface roughness decreases with an increase of the average asperity wavelength and reduction. The initial surface roughness affects the decrease rate of surface roughness when the reduction increases. The surface roughness of the oxide scale and steel is quite close when the rolling with lubrication and both of them are reduced with reduction, and the surface roughness of the oxide scale is reduced less comparing with that of without lubrication case. The calculated roughness is close to the measured data.
Authors: Anne Marie Huntz, S.C. Tsaï, J. Balmain, K. Messaoudi, Bernard Lesage, C. Dolin
Authors: Mohamad Nadzir Suraya, Amrin Astuty, B. Hariffin, Roslina Mohammad
Abstract: Grade T91 steel is one of a common material used for construction of superheater tubes in power generation boiler. In general, superheater tubes that operates in subcritical boiler are expose to operating temperatures in the range between 540°C to 580°C. Exposure to high temperature makes this steel subject to formation of oxide scale which can cause detrimental effect on the material properties. Excessive formation of oxide scale on internal surface of superheater tube can cause overheating damage at early stage of the boiler operation. This study was conducted to examine the behaviour of oxide scale forms on T91 steel for specimens exposed to temperature of 540°C for 200, 400, 600, 800 and 1000 hours holding time. The oxidation kinetic was identified as parabolic and the oxide scale was observed having 3 different layers which are haematite (Fe2O3), magnetite (Fe3O4) and spinel (Fe,Cr)2O3. The oxide scales layers were observed separated by voids and crack which are growing in size over time.
Authors: Somrerk Chandra-Ambhorn, P. Promdirek, Gobboon Lothongkum, Yves Wouters, Alain Galerie
Abstract: The tensile test, accompanied by the corresponding theoretical model, has been developed to quantify the mechanical adhesion energy of the oxide scale on metallic substrate in our previous works. The method to quantify the adhesion energy took into account the effect of residual stress. The effect of the variation of the measured residual stress on the quantified adhesion energy is assessed in this paper. For the scales failed at strains initiating the spallation of 0.018 and 0.011 followed by the transverse crack, it was found that the quantified adhesion energy of the oxide is not sensitive to the variation of the residual stress measured in the range from 0.5 to 2.0 GPa. This is due to the compensation of the decrease in stored energy due to the stress applied in the loading direction (x direction) and the increase in stored energy due to the stress applied in the direction perpendicular to the loading direction (y direction) when the residual stress increases. For the scale failed by the transverse crack followed by the spallation, the quantified adhesion energy tends to be sensitive to the variation of the measured residual stress. The assumption of energy relaxation during the tensile test is alternatively proposed. It is assumed that the energy stored due to the stress in x and y directions is totally released at the first crack. The energy stored due to the stress in y direction from strain initiating the crack to strain initiating the spallation is used in the quantification of the adhesion energy. The scatter of the adhesion energy values quantified by this method and those measured by the inverted-blister test is reduced comparing to the results reported in the previous work.
Authors: L. M. Zhu, J. H. Yang
Abstract: The microstructure and pickling characteristics of oxide scale formed on hot-rolled SPHC steel strip produced by different processes were investigated based on structure observation, weight loss and corrosion potential measurements. The results show that the scale formed on strip produced by TSCR consists of mainly magnetite (Fe3O4) and little wustite (FeO), hematite (Fe2O3), and that in conventional process is composed mainly wustite (FeO) and little magnetite (Fe3O4), hematite (Fe2O3). The shape of the open-circuit potential transient is determined crucially by the oxide scale structure. Time to reach a steady-state value of open-circuit potential of strip produced by TSCR is longer than that in conventional process. Both the stability of the scale in pickling solution and the effectiveness of descaling could be evaluated and predicted by measuring the change of electrochemical potential during acid pickling.
Authors: Xin Long Yang, Hui Xin Dai, Xiang Li
Abstract: In recent years, the steel industry is in decline. To reduce environmental pollution, increase corporate profits and promote the sustainable development of China's steel industry, developing steel metallurgical slags comprehensive utilization has a very important significance. This article describe the present situation and problems in China's steel metallurgy slag comprehensive utilization, and reach the conclusion that the present method should be improved and the new method of comprehensive utilization should be further developed.
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