DP980超高强钢激光焊接接头组织及性能研究

发布时间：2018-04-13 17:42

本文选题：DP超高强钢 + 激光焊接　；参考：《天津大学学报(自然科学与工程技术版)》2017年03期

【摘要】：利用Nd:YAG固体激光器对DP980超高强钢进行激光对接焊接,通过硬度测试、拉伸试验研究DP980超高强钢激光焊接接头力学性能的变化,采用光学显微镜(OM)、扫描电子显微镜(SEM)等观察显微组织的转变.结果表明:DP980超高强钢经过激光焊接,焊接接头分为焊缝金属区、完全相变区、不完全相变区、回火区和母材区.焊后焊缝金属区和完全相变区为马氏体组织,硬度较高;焊接接头软化现象发生在不完全相变区和回火区:不完全相变区马氏体发生相变使得铁素体含量增加;回火区组织发生回火,马氏体析出碳化物,导致软化.在力学性能方面,焊接接头抗拉强度略有降低,延伸率下降明显,软化区的存在导致在拉伸试验时焊接接头的不均匀变形,造成了其塑性明显下降;拉伸试样的断裂发生在焊接接头热影响区,断口观察发现存在有大小不等、深浅不一的韧窝,属于塑性断裂.
[Abstract]:Laser butt welding of DP980 ultra-high strength steel was carried out by using Nd:YAG solid-state laser. The mechanical properties of laser welded joint of DP980 ultra-high strength steel were studied by hardness test and tensile test.Optical microscope and scanning electron microscope (SEM) were used to observe the transformation of microstructure.The results show that the welded joints are divided into weld metal zone, complete phase transition zone, incomplete phase transition zone, tempering zone and base metal zone.After welding, the weld metal zone and complete transformation zone are martensite structure with high hardness, and the softening of welded joint occurs in incomplete transformation zone and tempering zone: martensite transformation in incomplete transformation zone makes the content of ferrite increase.Tempering occurs in the tempering zone and martensite precipitates carbides leading to softening.In terms of mechanical properties, the tensile strength and elongation of welded joints decreased slightly, and the existence of softening zone resulted in uneven deformation of welded joints during tensile tests, which resulted in a marked decrease in plasticity.The fracture of tensile specimen occurs in the heat-affected zone of welded joint, and the fracture surface observation shows that there are dimples of varying size and depth, which belong to plastic fracture.
【作者单位】：天津大学材料科学与工程学院;湖北汽车工业学院材料科学与工程学院;
【基金】：国家自然科学基金资助项目(51175374) 先进焊接与连接国家重点实验室开放基金资助项目(AWJ-Z15-03)~~
【分类号】：TG456.7

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