| ZHANG Lishuai,GUO Tieming,WU Weihong,HU Yanwen,LIU Xiaoqian,NAN Xueli,ZHOU Guiyi,YI Weibin.Wet-dry Cycle Corrosion Behavior of Q420qENH Steel and Its Welded Joint in Simulated Industrial Atmosphere Containing PM2.5[J],53(2):97-109 |
| Wet-dry Cycle Corrosion Behavior of Q420qENH Steel and Its Welded Joint in Simulated Industrial Atmosphere Containing PM2.5 |
| Received:November 18, 2022 Revised:May 15, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.02.009 |
| KeyWord:Q420qE bridge weathering steel welded joints northwest industrial atmospheric environment PM2.5 SiO2 dry-wet cycle corrosion |
| Author | Institution |
| ZHANG Lishuai |
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou , China |
| GUO Tieming |
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou , China |
| WU Weihong |
Gansu Provincial Transportation Planning Survey and Design Institute Co., Ltd, Lanzhou , China |
| HU Yanwen |
Gansu Provincial Transportation Planning Survey and Design Institute Co., Ltd, Lanzhou , China |
| LIU Xiaoqian |
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou , China |
| NAN Xueli |
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou , China |
| ZHOU Guiyi |
State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou , China |
| YI Weibin |
Gansu Precision Machining Technology and Equipment Engineering Research Center, Lanzhou , China |
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| Abstract: |
| In this work, the corrosion behavior of Q420qENH weathering steel and its welded joints in industrial atmospheric environment containing PM2.5 was studied by dry-wet alternate accelerated corrosion test. The corrosion trend, corrosion type and rust layer protection of the plate, weld and heat affected zone samples, and the effect of SiO2 on corrosion were investigated. In the industrial atmospheric medium containing SiO2, the initial corrosion rate of Q420qENH plate sample was higher than that of the welding sample, and the corrosion rate of the two samples gradually decreased and tended to be the same in the middle and late period. During the entire corrosion process, the n values of the plates and welded samples were all less than 1, indicating that the corrosion of Q420qENH steel plates and welded samples was a deceleration process in the northwest industrial atmospheric medium environment containing PM2.5. The corrosion types were characterized by general corrosion and local corrosion, but the local corrosion pit size of the plate was large and the corrosion was serious. The outer rust layer of the three samples was loose and easy to fall off, and there were defects such as long cracks and holes. However, the rust layer in the weld and heat affected zone was denser than the plate and closely bonded to the steel matrix, and the content of Cu and Ni elements in the rust layer was significantly higher than that of the plate sample. The three samples all had obvious element enrichment phenomenon, and the Si element enrichment in the rust layer of the weld and heat affected zone samples was less than that of the plate, which indicated that the inner rust layer formed by the weld and heat affected zone samples could be more concentrated. The self-corrosion current of the three samples after corrosion for 30 days wa:plate > weld > heat affected zone, and the self-corrosion potential wa:heat affected zone > weld > plate. The rust layer resistance of the weld and heat affected zone samples was 1.28 times and 1.68 times that of the plate samples, respectively, indicating that the protection of the rust layer formed by the heat affected zone and the weld was better than that of the plate samples, and the corrosion resistance was better than that of the plate samples. This was because the microstructure of the weld and the heat affected zone was a large amount of acicular ferrite, granular bainite and lath bainite formed in the original austenite grains. The microstructure was fine and uniform and the grain boundary was weakened, which was beneficial to the improvement of corrosion resistance. In addition, the higher Cu and Ni elements in the weld could promote the transformation of γ-FeOOH to α-FeOOH, which increased the ratio of α-FeOOH/γ-FeOOH of the welded sample, improved the compactness and stability of the rust layer, and thus improved the corrosion resistance. The PM2.5 with SiO2 as the main component is easy to deposit at the defects, which becomes the nucleation substrate of the corrosion products, promotes the non-uniform nucleation of the corrosion products, and makes the rust layer develop unevenly, so it is not conducive to the compactness of the rust layer. |
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