Abstract
In order to better understand the formation mechanism of tertiary oxide scale in high-strength steel during hot rolling, the microtexture of the oxide layer has been characterized and analyzed by the electron backscatter diffraction (EBSD) method. The results show that the Fe3O4 phase in the oxide layer has a two-phase heterogeneous morphology, Fe3O4 in the oxide layer comprises columnar grains, and Fe3O4 near the substrate comprises spherical grains. As the reduction rate increases, the Fe2O3 layer is gradually wedged into the surface of the Fe3O4 layer. Fe3O4 forms a <110> fiber texture at a reduction rate of 10%. The inner layer of the oxide scale comprises spherical grains, and Fe3O4 is preferentially nucleated and precipitated in the direction of Fe surface grains <110> texture. With the increase in the reduction rate, the {112}<−1−21> directional slip system shows the lowest Schmidt factor value, so the grains with a low Schmidt factor exhibit higher stored strain energy. The formation of the spherical Fe3O4 seam layer close to the steel matrix is the result of the combined effect of the stress state at the matrix and ion diffusion.
Highlights
Since hot-rolled steel sheets are always produced in high-temperature environments, oxide scale is always accompanied by the entire process, and it is inevitably formed on the surface of the steel
As the proportion of α-Fe in the steel matrix was much higher than the content of pearlite, only the α-Fe phase was selected for the steel matrix in the electron backscatter diffraction (EBSD) analysis
When the reduction rate increases from 10% to 27%, the matrix grains are elongated, and the number of sub-grains increases
Summary
Since hot-rolled steel sheets are always produced in high-temperature environments, oxide scale is always accompanied by the entire process, and it is inevitably formed on the surface of the steel. Proper control is related to the surface quality of the final product [1,2]. Before subsequent processing such as cold rolling, the steel plate needs to be pickled to remove the scale. It is very important to understand the origin of pickling-free steel, which is closely related to the deformation behavior of the oxide scale on the surface of the hot-rolled steel. Fe2 O3 is distributed on the surface of the oxide layer and the content is low [5,6,7]
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