Effect of Si content and surface defects on hot-dip galvanizing layer of Q235 hot-rolled steel sheet
NIU Yue-wei1,2, LI Yi-lun3, LIU Chao3, YANG Zhi-gang1,2, HUANG Wei-li1,2, YANG Shu-feng4
1. Technology Center, Delong Steel Co., Ltd., Xingtai 054009, Hebei, China; 2. Hebei Hot Rolled Plate and Strip Technology Innovation Center, Xingtai 054009, Hebei, China; 3. Institute for Advanced Materials and Technology, University of Science and Technology, Beijing 100083, China; 4. School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing 100083, China
Abstract：In order to study the effect of Si content and surface defects on hot-dip galvanizing layer of Q235 hot-rolled steel sheet, the cross-sectional morphology, thickness and element distribution for hot-rolled steel sheets of Q235 with different Si content and different surface physicochemical properties under the same dip coating conditions were investigated using coating thickness gauge, scanning electron microscopy and energy spectroscopy and so on. The results show that, when the mass fraction of Si element is greater than 0.15%, the Zn-Al phase decreases and the pure Zn phase concentrates due to the bias of Al elements, and abnormal Fe-Al intermetallic compounds grows at the interface, leading to increase in the thickness and decrease in the bonding strength of the layer. The absence of Fe-Al intermetallic compound layer due to holes in the plating for flame-cut side of the steel is found, leading to inward expansion of the layer and uneven layer thickness. Therefore, the mass fraction of Si element in Q235 steel used for hot-dip galvanizing should be controlled below 0.15%, and the use of flame cutting process can be reduced, or the surface treatment of the flame-cut plate can be carried out to improve the quality of the steel surface plating.
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NIU Yue-wei, LI Yi-lun, LIU Chao, YANG Zhi-gang, HUANG Wei-li, YANG Shu-feng. Effect of Si content and surface defects on hot-dip galvanizing layer of Q235 hot-rolled steel sheet[J]. China Metallurgy, 2023, 33(3): 85-93.
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2023, Vol. 33 
