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Liu L.,University of Science and Technology Beijing | Liu L.,Shougang Institute of Technology | Jiang G.,Shougang Institute of Technology | Ma B.,Beijing Shougang Cold Rolled Sheet Co. | And 3 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2014

Generation mechanism of dark dot defect and effect on painting surface quality of hot-dip galvanized steel sheet were studied, and some relative improvement measures were proposed. The results show that little pits exist on the substrate, which form dark dot defect is composed of oxide film after galvanized. The dark dot defect markedly influences crystal structure of phosphate coating. Moreover, during practical production, it could be effectively reduced by decreasing coiling temperature, reducing current density in rinse tank and improving sealing of the annealing furnace.


Hui Y.-J.,University of Science and Technology Beijing | Li W.-Y.,University of Science and Technology Beijing | Zhao A.-M.,University of Science and Technology Beijing | Cai A.-Y.,Beijing Shougang Cold Rolled Sheet Co. | And 2 more authors.
Journal of Iron and Steel Research | Year: 2013

The formation of oxide scale of the hot rolled strip wassimulated at different temperature by holding different time, and then, the microstructure and morphology of the oxide scale were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction. The results show that the oxide scale on the surface of the steel has three layers, composed of wustite, magnetite and hematite, magnetite and hematite are compact. With the increase of the holding time at the same temperature, the thickness of the oxide scale increases. The mesh crack of the oxide scale is the main reason for the oxidation kinetic curves turn from parabolic law to linear law. The problem that the thickness of the oxide scale cannot be directly measured is solved by this simulation method, and it can provide a reference for oxide scale thickness control by adjusting the process parameters.


Wang H.-H.,Control Iron and Steel Research Institute, China | Qi C.-Y.,Beijing Shougang Cold Rolled Sheet Co LTD | Li Y.-P.,Control Iron and Steel Research Institute, China | Jiang S.-M.,Control Iron and Steel Research Institute, China | And 2 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015

Effects of dew point on the galvanizability of DP590 before galvannealing were studied, and the morphology and type of oxides on the surface of DP590 and the cross-sectional structure and subsurface structure under different dew point were studied by SEM and XPS. The results show that the morphology of oxides on the DP590 surface is affected by dew point, with dew point changing from -10℃ to -50℃, the density of oxides on DP590 surface first increases and then decreases, oxides type of Mn and Cr is not affected by dew point, while Si affected. As a result of influence on morphology of oxides on the DP590 surface, changes of dew will then affect the diffusion of Fe and Zn, at last affect the cross-sectional and subsurface structure, with dew point changing from -10℃ to -50℃, Fe-Zn phase first increases and then decreases. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.


Qi C.,Control Iron and Steel Research Institute, China | Qi C.,Beijing Shougang Cold Rolled Sheet Co. | Wang H.,Control Iron and Steel Research Institute, China | Li Y.,Control Iron and Steel Research Institute, China | And 3 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2015

To analyze the effect of galvannealing (GA) parameters on the alloying behavior of DP590 dual phase steel plate, SEM, surface roughness measuring instrument were applied to investigate the surface morphology, cross-sectional structure and surface roughness of the galvannealed coatings under different GA processes. The results show that with GA temperature rising and GA time prolonging, the content of ζ phase decreases and the content of δ phase increases, and small holes appear on the surface of the coating. When GA temperature is 480℃, surface roughness of the galvannealed coating on DP590 steel plate increases with the prolonging of time. While GA temperature is 500℃ and 520℃, the surface roughness decreases with time extension. When GA time is 25 s, the surface roughness decreases with the rising of temperature. While GA time is 20 s, with the rising of GA temperature, the surface roughness decreases first and then increases. With GA temperature rising and GA time extending, alloying degree deepens, and Γ phase appears in the galvannealed coating when GA temperature is 520℃ and GA time is 25 s. ©, 2015, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.

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