目的 研究热处理参数对焊接接头组织和性能的影响规律,为进一步优化性能提供理论和试验依据。方法 采用窄间隙氩弧横焊的方法完成了40 mm板厚的核电转子试板焊接,并对比了4种热处理工况（焊态、590 ℃×16 h、590 ℃×20 h、590 ℃×28 h）下焊缝的金属性能,对力学性能试验后的试样进行了光学显微组织分析、SEM扫描、电子背散射衍射等微观结构的定量表征。结果 与焊态相比,热处理后焊缝金属屈服强度普遍降低了100 MPa左右,抗拉强度降幅在70 MPa左右。焊缝金属的韧性在热处理后同步发生了大幅度降低,在室温20 ℃和0 ℃下,焊缝金属的冲击韧性普遍降低了50%以上。保温时间的延长对焊缝强度和室温冲击的影响降幅较为平缓,但是在0 ℃条件下,冲击韧性则表现出50%以上的减幅,且离散性更强。结论 晶界边缘的碳化物状态出现了显著变化,碳化物的析出数量和密度明显增加,形成了连续的碳化物析出相,在力学性能的外部载荷作用下,原有晶界的位错阻断作用大幅减弱,裂纹的快速扩展在宏观上表现为接头的拉伸性能和冲击性能严重劣化。
Abstract
The work aims to investigate the influence law of heat treatment parameters on the microstructure and properties of welded joints, and provide a theoretical and experimental basis for further performance optimization. Welding of 40 mm thick nuclear power rotor test plates was completed by narrow-gap GTAW horizontal welding. The properties of weld metal under four heat treatment conditions (as-welded, 590 ℃×16 h, 590 ℃×20 h, 590 ℃×28 h) were compared. Quantitative microstructural characterizations including optical microstructure analysis, SEM scanning and electron backscatter diffraction (EBSD) were carried out on the specimens after mechanical property tests. Compared with the as-welded state, the yield strength of weld metal after heat treatment decreased by about 100 MPa on average, and the tensile strength decreased by approximately 70 MPa. The toughness of weld metal also decreased significantly after heat treatment, and the impact toughness at room temperature (20 ℃) and 0 ℃ decreased by more than 50% in general. Prolonging the holding time led to a gentle decline in weld strength and room-temperature impact toughness, while the impact toughness at 0 ℃ was reduced by over 50% with stronger dispersion. In conclusion, the carbide morphology at grain boundaries changes remarkably; the precipitation quantity and density of carbides increase obviously, forming continuous carbide precipitation networks. Under external loading for mechanical properties, the dislocation blocking effect of original grain boundaries is greatly weakened, and the rapid crack propagation macroscopically results in serious deterioration of tensile and impact properties of the joint.
关键词
低合金高强钢 /
热处理 /
窄间隙氩弧 /
碳化物
Key words
low-alloy high-strength steel /
heat treatment /
narrow-gap GTAW /
carbide
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基金
材料结构精密焊接与连接全国重点实验室开放课题（AWJ-24M09）; 辽宁材料实验室-鞍钢集团有限公司先进金属材料产业技术创新中心重大专项（LAC2023ZSC300）
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