为了研究300M低合金超高强度钢激光焊接接头的组织和力学性能,采用光纤激光器对300M钢进行自熔焊对接试验,结合拉伸测试等分析方法研究了焊接接头的焊缝形貌、组织变化特征和力学性能,讨论了焊缝金属快速凝固过程中的相变。结果表明:300M低合金超高强度钢激光焊接接头的焊缝横截面呈典型的“Y”形;焊缝金属主要由柱状树枝晶组成;焊缝组织主要由马氏体以及残余奥氏体组成。靠近焊缝的热影响区分为硬化区和软化区,硬化区的硬度约为734 HV,软化区的硬度约为456 HV,接头的断裂位置为软化区,接头的抗拉强度为1269 MPa,约为母材强度的65%。

In order to study the microstructure and mechanical properties of laser welded joint of 300M low alloy ultra-high strength steel, fiber laser is used to perform the self-fusion welding butt test of 300M steel. The weld morphology, microstructure change, and mechanical properties of welded joints are studied by means of tensile test and other analytical methods. The rapid solidification process of weld metal is discussed. The results show that the weld cross-section of the laser welded joint of the 300M low alloy ultra-high strength steel has a typical "Y" shape. The weld is mainly composed of columnar dendrites, and the weld structure is mainly composed of martensite and retained austenite. The heat effect near the weld is divided into a hardened zone and a softened zone. The hardness of the hardened zone is about 734 HV, the hardness of the softened zone is about 456 HV, the fracture location of the joint is the softened zone, and the tensile strength of the joint is 1269 MPa, which is about the 65% of the strength of host material.