The effect of temperature on oxide scale adherence during descaling operations (original) (raw)
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Oxidation of Metals, 2017
The Deflection Test in Monofacial Oxidation (DTMO) was used to assess the parameters of a phenomenological model aimed to represent the mechanical behavior of the martensitic T91 steel during oxidation at 550°C under wet atmosphere. The constitutive equations of the mechanical model were determined from the knowledge of the growth mechanism of the oxide scale. Some model parameters were found in the literature and complementary data were obtained by the comparison between experimental DTMO curve and simulated results.
Chemical Descaling of High Temperature Oxides Formed on Low Alloy Steels
2012
Introduction The dissolution processes of “low temperature” thermal oxide layers (Fe3O4|Fe2O3) on iron and steels have been studied in acid solutions for over 80 years 1, 2 . Even though, many questions about the pickling mechanism of high temperature Fe(1-x)O-containing scales remain open. It was early proposed 2, 3 that the cathodic reactions involved in the dissolution of Fe3O4 and Fe2O3 in HCl solutions are most probably: 1) the reductive dissolution of ferric oxide, 2) oxygen reduction reaction (ORR) and 3) the hydrogen evolution reaction (HER). In the case of the acid pickling of the same oxides in 0.1 M H2SO4 solution, it was suggested 4 that the rapid dissolution of the oxide films, when in contact with the metal substrate would be due to the formation of the cell “metal|acid|ferric oxide”. In this cell, the cathode would be the ferric oxide and could be quickly reduced to ferrous oxide, which would dissolve. It was early identified by Pryor and Evans 2 that during the disso...
Impact of Oxide Scale on Heat Treatment of Steels
2014
Oxidation is an inherent aspect of steel production and heat treatment. Oxide scale layers commonly impact surface quality and material loss during steel processing. This paper is focused on the study of the influence of the oxide layer on cooling intensity. Spray cooling of a hot steel surface is considered. Typical examples are secondary cooling in continuous casting, interstand and run-out table cooling at hot rolling, and heat treatment and other metallurgical processes where controlled temperature regimes are required. Cooling intensity is primarily affected by spray parameters such as pressure and coolant impingement density. Though not frequently reported, even thin layers of oxides can significantly modify cooling intensity. This effect is prevalent when cooling steel surfaces at high surface temperatures. The influence of oxide scale layers on cooling intensity was studied using experimental measurements and numerical analysis. Experimental measurements compare the cooling ...
Examination of Oxide Scales of Hot Rolled Steel Products
ISIJ International, 2005
Porosities in the scale layer and wavy scale-steel interfaces are two common artefacts generated during metallographic preparation of oxide scale samples. This paper presents the techniques used by the authors to effectively remove porosities in the scale and reduce the waviness of the scale-steel interface so that the true scale structures can be examined. The techniques have been successfully applied to the examination of oxide scales on hot-rolled steel with various thicknesses and structures.
OXIDATION OF METALS, 2011
The influence of surface preparation on the stress and adhesion of oxide scales formed on the ferritic stainless steel AISI 441 was studied. Steel coupons were surface-finished to different degrees of surface roughness from 400-grit SiC through to 1-micron diamond, and were also electropolished to remove the work hardened surface. Initial metal roughness was measured by optical profilometry. Oxidation was carried out at 800°C under synthetic air for 100 h. Oxide residual stress was derived from the Raman shift of the main chromia line, and adhesion of oxide scales was quantitatively obtained using forced spallation by tensile straining. The results show that surface hardening is the most influential factor on adhesion, with the high dislocation-containing mirror-polished samples exhibiting the lowest adhesion energy (*4 J m-2), and the electropolished samples with non-mechanically affected surface exhibiting the highest adhesion energy (17 J m-2). Recrystallisation of the subsurface zone during heating to the oxidation temperature is thought to be the most influential factor reducing scale adhesion.
Materials Science and Engineering: A, 2003
The inverted blister test was used to study the adhesion of chromium-rich oxide scales thermally grown on several ferritic stainless steels. With this technique, a quantitative determination of the adhesion energy of the oxide on its substrate was possible. The adhesion energy is found to vary between 3 and 170 J m (2 depending on the specimens. It appears that the parameters influencing adhesion are oxide thickness and the nature of the minor alloying elements present in the alloy. The microstructural observation of both sides of the oxide/alloy interface after debonding provides important information on adhesion and spallation. #
Journal of Metals, Materials and Minerals
This article addresses applying a tensile test with a CCD camera to assess scale adhesion on hot-rolled steel as a function of hot-rolled coil position. The scale adhesion in this study was shown in the value of the strain initiating the first scale spallation. The result of strain initiating the first scale spallation was confirmed with an acoustic emission (AE) method. The as-received hot-rolled coil was studied at the head, middle, and tail positions. A scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to examine the scale morphology and phase identification respectively. The results show that the oxide scale comprises hematite and magnetite layers. It was found that the higher strain initiating the first scale spallation was revealed on the scale formed on the hot-rolled coil at the head and middle positions. This indicates that the oxide scale was more difficult to remove than at the tail position of the coil. The scale growth and cooling affects the stre...
Effect of grain-refined microalloyed steel substrate on formation mechanism of tight oxide scale
Corrosion Science, 2014
The formation mechanism of tight oxide scale on the microalloyed steel was investigated at temperatures of 550-850°C in dry air. Microstructural characterisations reveal that the spallation of oxide scale dominates at the centre of coarse grains on the oxidation initiation. The fine-grained steel improves the adhesive properties of oxide scale by enhanced grain-boundary diffusion. The lower activation energy and higher oxidation rate accelerate cation/anion migration along grain boundaries, leading to high magnetite content in the oxide scale. The approach by grain refinement at initial oxidation has been proposed to generate the pickle-free tight oxide scale.
Study of the morphology of oxide scale formedon hot-rolled steel
2014
Mechanism of oxide scales formation on steel during hot rolling process is delicately determined and their structures are extremely complex. This work is part of larger studies made to understand the oxide scale behavior. Therefore, the morphology of oxides is determined by optical microscopy. Identification of the mechanical properties of oxide scales is achieved by micro-hardness measurement. The work has revealed a variation of microstructure in several layers of oxide. It was obtained that the oxide scales consisting mainly of wustite FeO, magnetite Fe3O4 and hematite Fe2O3 owing to the formation of voids and cracks in the scales, especially on the outer layer where it is high porous. The intermediate layers is thicker than others oxide layers. The outer layer has a lowest hardness and highest porosity.
HAL (Le Centre pour la Communication Scientifique Directe), 2014
Two austenitic stainless steels, AISI 304L and AISI 303, containing 0.025 and 0.249 wt%S were oxidized in thermobalance at 1000°C for 50h. The chemical composition and the crystallographic structure of the oxide scales were investigated by Raman spectroscopy. Adhesion of oxide scales was tested by SEM in situ tensile tests. A correlation between the specific mass change, the chemistry, the microstructure and the adhesion properties is made and results are discussed in relation with sulphur concentration in the alloy.