不同雷电流分量作用下钢合金Q235B的损伤与温升特性

Damage Characteristics and Temperature Rise of Steel Alloy Q235B Suffered From Different Lightning Current Components

研究工业常用材料钢合金Q235B的雷击损伤和温升特性是油罐等防雷保护的关键基础之一。为此,采用模拟雷电流试验方法研究钢合金Q235B的雷击损伤与温升特性,通过高分辨扫描电子显微镜(SEM)、X射线能量色散分析(EDS)和显微硬度测量仪观测合金遭受雷击后的表面损伤形貌、剖面损伤组织特征、元素含量变化和显微硬度变化,建立雷电流金属温升模型,分析合金温升变化及其与合金微观损伤组织形貌的对应关系。结果表明:幅值为201.2kA的首次短时间回击电流分量作用下合金的损伤面积最大,可达3523.8mm2;转移电荷量为210.1C的末次回击后长持续时间雷电流造成合金的损伤深度最深,为3.0mm;后续短持续时间回击电流分量下合金的损伤深度和温升可忽略不计。电流幅值为404A的末次回击后长持续时间雷电流分量作用下合金剖面在不同温升激励下出现了以马氏体为主相的损伤区、以马氏体与铁素体为主相的过渡区、以铁素体与珠光体为主相的基体的分层结构,损伤区和过渡区的临界形成温度分别为990℃和900℃,损伤区、过渡区和基体的显微硬度分别为450、310和180。

Research on the damage characteristics and temperature rise of steel alloy Q235 B subjected to lightning currents is the basis for the lightning protection of oil tanks. Therefore, the simulated lightning experiment was carried out to investigate its damage characteristics and temperature rise. The high-resolution scanning electron microscope(SEM), energy dispersive spectrometer(EDS), and micro-hardness tester were adopted to investigate the damage morphology on the surface, microstructure in cross-section, element composition and micro-hardness changes, respectively. The response of metal microstructures to temperature was analyzed by a proposed lightning-metal temperature rise model. Results show that, the first return stroke current with amplitude of 201.2 kA results in the largest damage area of 3523.8 mm2. The long continuing current with charge transfer of 210.1 C leads to the deepest damage depth of 3.0 mm. The damage depth and temperature rise caused by the subsequent stroke current can be neglected. Suffered from the long continuing current with amplitude of 404 A, the demixing phenomenon occurs on the cross section and is divided into three zones, which are the damage zone mainly consisting of the Martensite with formation temperature of 990 ℃, the transition zone of mainly the Martensite and Ferrite transferred at 900 ℃, and the origin zone of the Pearlite and Ferrite. The hardness of the three zones are 450, 310, and 180, respectively.