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基于模拟雷电流试验方法研究了回击后长持续时间雷电流分量作用下Q235合金钢的损伤特征。用光学显微镜、场发射扫描电镜(XR-SEM)、X射线能谱仪(EDS)和自动硬度计分析了试样的损伤形貌、不同区域的元素含量和材料损伤后的硬度分布。结果表明:在回击后长持续时间雷电流分量作用下,Q235钢试样剖面的微观组织形貌出现了明显的分层,分别为氧化层,马氏体(损伤区),马氏体与铁素体(过渡区),铁素体与珠光体(基体)。试样的显微硬度值随马氏体含量下降而下降,由损伤区的450 HV0.5降至基体的180 HV0.5。在电热应力作用下,裂纹的萌发发生在试样表面凹坑边缘、损伤区的气孔周围和元素分布不均匀区域。
The damage characteristics of Q235 alloy steel under long-duration lightning current were studied based on simulated lightning current test. The damage morphology, the content of elements in different regions and the hardness distribution after material damage were analyzed by optical microscope, field emission scanning electron microscope (XR-SEM), X-ray energy dispersive spectrometer (EDS) and automatic hardness tester. The results show that the microstructure of the Q235 steel specimen shows obvious delamination under the action of lightning current component of long duration after the strikeback, which are the oxide layer, the martensite (damage zone), martensite and iron Body (transition zone), ferrite and pearlite (matrix). The microhardness of the sample decreased with the decrease of martensite content, from 450 HV0.5 in the damaged area to 180 HV0.5 in the matrix. Under electrothermal stress, the crack germination occurs on the edge of the pit on the surface of the specimen, around the pores of the damaged area and in the non-uniform distribution of the elements.