Study of strip-shaped chromatic aberration defects on the surface of an electro-galvanized fingerprint-resistant sheet

Abstract; Strip-shaped chromatic aberration defects on the surface of an electro-galvanized fingerprint-resistant sheet were systematically studied using Thermo-Calc thermodynamic calculations, scanning electron microscope and X-ray diffractometer analyses,and rapid heat treatment simulation technology. The formation mechanism of these defects was also analyzed. The results show a strong correlation between the defects and the uneven distribution of the Fe(001) componet on the surface of the steel substrate. The relatively high proportion of Fe(001) components on the surface of the steel substrate afects the distribution density of the Zn crystal cells in different orientations during the electrodeposition process, which causes the reflection intensity of the light of the galvanized layer to differ from various visual perspectives, and macroscopic strip-shaped chromatic abereation defects ae fnally formed. The high proportion of the Fe(001) component on the surface of the steel substrate is mainly related to the following two factors. First, when the strip steel is hot-rolled, the fnishing hot-rolling temperature is close γ the α ^ a phase tansition temperature. When the local temperature on the upper surface of the strip steel is low, γ + a two-phase rolling easily occurs, and this results in an uneven stess distribution between the y and a phases after the hot-rolling process. This uneven distribution of hot-rolling stess results in the formation of a coarse grain structure in the local area on the surface of the hot-rolled sheet, which storngly affects the subsequea cold rolling and annealing process, and the annealed steel sheet substrate ultimately contains a greater proportion of the Fe (001) component. And second,a fast cooling rate ( >10 К/s) during the slow cooling stage in the continuous annealing process inhibits the transformation of the Fe(001) to the Fe(lll) component on the surface of the cold-rolled steel sheet,and it is then not possible to effectively eliminate the nriluence of the unevenly distributed Fe(00 1 ) component on the surface of the annealed steel sheet (originating from the uneven hot-rolled microstructure). This uneven distribution of the Fe(00 1 ) component on the surface of the annealed steel sheet following the continuous annealing heat treatment has a stong effect on the electrodeposition behavior of the Zn crystal cell in the subsequent electoplating process and the formation of macroscopic strip-shaped chromatic aberrat