耿迎新, 周梦然, 赵义焜, 李嘉熙, 王璇, 叶壮壮, 陈高强, 史清宇. 应变速率对特高压变压器油箱Q345钢焊接接头动态失效行为的影响[J]. 金属学报, DOI: 10.11900/0412.1961.2025.00121.

摘要 相关文章 Metrics 全文: PDF(1890 KB)   摘要: 为保障特高压变压器油箱的防爆性能，本工作聚焦其关键结构Q345钢焊接接头在动态冲击载荷下的变形行为和失效机制，采用数字图像相关辅助的拉伸测试、冲击测试、SEM观察以及计算机断层扫描等方法，研究了油箱用Q345钢焊接接头在不同应变速率下的变形行为和失效机制。结果表明，与Q345钢母材相比，焊接接头的变形行为对应变速率更为敏感。当应变速率提升至1.0 × 10-1 s-1时，其延伸率显著降低，撕裂位置由母材区域转移至焊缝区域。在冲击载荷作用下，变形过程中的绝热升温现象促使材料内部形成氧化物颗粒，这些颗粒作为潜在的裂纹源，易造成应力集中，从而加剧油箱焊缝的结构失效。Q345钢母材的冲击韧性为(326.1 ± 14.1)  J/cm2，焊接接头的冲击韧性仅为 (52.7 ± 2.7) J/cm2，母材的冲击韧性约为焊接接头的6倍，表明焊缝区域是增强油箱防爆性能的关键部位。在模拟接近电弧放电产生的超高速冲击速率载荷下，焊缝区域观察到典型的解理断裂，是导致其冲击韧性大幅降低的原因。 关键词 ： 变压器油箱,  Q345钢,  焊接接头,  应变速率,  变形行为     Abstract：Ultra-high-voltage transformer tanks are critical structural components of large-scale power and converter transformers and require exceptional explosion-proof performance to ensure grid stability. These tanks are typically fabricated from low-alloy high-strength steels such as Q345 and are characterized by complex geometries and a high density of welded joints. During internal arc discharge events, welded joints serve as primary sites for crack initiation and propagation under transient impact loading, ultimately leading to structural failure. Although welded joints are recognized as potential weak links, their strain rate-dependent deformation behavior and underlying failure mechanisms have not been systematically elucidated. In particular, it remains unclear how dynamic loading conditions affect fracture initiation sites and the evolution of microstructural damage within welded joints. In this study, the deformation behavior and failure mechanisms of Q345 steel welded joints were systematically investigated. Uniaxial tensile tests were conducted over a strain rate range of 1.0 × 10−4 s−1–1.0 × 10−1 s−1, coupled with digital image correlation to monitor the evolution of localized strain fields. Impact toughness was evaluated using standard Charpy tests, and microstructural characterization was conducted using optical microscopy and SEM. Furthermore, X-ray computed tomography was employed to visualize and quantify internal defect evolution. The results indicate that Q345 steel welded joints exhibit more pronounced strain rate sensitivity than the base metal (BM). As the strain rate increased to 1.0 × 10−1 s−1, a substantial reduction in elongation was observed. Meanwhile, the fracture initiation site shifted from the BM to the weld metal (WM) with increasing strain rate. Digital image correlation analysis revealed a transition in fracture location. At lower strain rates, plastic deformation was primarily accommodated by the BM, leading to necking and final failure within the BM region. In contrast, at higher strain rates, strain localization rapidly developed within the heat-affected zone and WM, resulting in fracture initiation in the weld region. Quantitative impact testing further demonstrated a substantial disparity in toughness. The BM exhibited a high impact toughness of (326.1 ± 14.1) J/cm2, whereas the welded joints showed a significantly lower value of (52.7 ± 2.7) J/cm2, corresponding to an approximately sixfold reduction. This marked decrease identifies the weld region as the dominant failure site and underscores its critical role in improving explosion resistance. SEM fractography confirmed a transition from ductile dimple morphology to brittle cleavage fracture, characterized by distinct cleavage facets and river patterns. Adiabatic heating during rapid plastic deformation was found to promote the formation of oxide particles within the welded joint. These oxides induced localized stress concentrations and acted as critical crack initiation sites, ultimately triggering structural failure. In addition, X-ray computed tomography results verified that large internal defects within the WM served as preferential sites for strain concentration and crack propagation under dynamic loading. This study clarifies the intrinsic mechanisms governing dynamic failure in Q345 steel welded joints and provides essential theoretical insights for improving the explosion resistance and structural integrity of welded steel components under extreme dynamic conditions. Key words： transformer tank    Q345 steel    welded joint    strain rate    deformation behavior 收稿日期: 2025-05-08      基金资助:国家电网有限公司总部科技项目(5500-202355352A-2-1-ZX) 服务 把本文推荐给朋友 加入引用管理器 E-mail Alert RSS 作者相关文章 耿迎新 周梦然 赵义焜 李嘉熙 王璇 叶壮壮 陈高强 史清宇 44.8K 链接本文: https://www.ams.org.cn/CN/Y0/V/I/0 [1] 张天昊, 鞠泉, 蒙肇斌, 王浩, 胡本芙. GH3230合金薄板填丝钨极氩弧焊接头的组织稳定性[J]. 金属学报, 2025, 61(9): 1375-1386. [2] 吴泽威, 颜俊雄, 胡励, 韩修柱. 双峰分离非基面织构AZ31镁合金板材反常中温轧制变形行为及机理[J]. 金属学报, 2025, 61(8): 1165-1173. [3] 姜沐池, 宫继双, 杨兴远, 任德春, 蔡雨升, 李秉洋, 吉海宾, 雷家峰. Ti30Ni50Hf20 高温形状记忆合金的热变形行为[J]. 金属学报, 2025, 61(6): 857-865. [4] 周任远, 朱丽慧. Inconel 740H焊接接头不同温度蠕变后 γ′贫化区的形成及其对力学性能的影响[J]. 金属学报, 2025, 61(5): 744-756. 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