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采用5 kWCO_2激光焊接超高强度30CrMnSiNi2A钢,以获得性能优良的焊接接头。利用光学显微镜(OM)、X射线衍射(XRD)、电子扫描显微镜(SEM)、显微硬度仪、电子万能试验机和X射线应力测定仪对激光焊接接头的显微组织、硬度、抗拉强度、拉伸断口和残余应力进行了研究。结果表明,焊缝中心区组织为等轴晶,近中心区组织为枝状晶,边缘区组织为粗大的柱状晶,熔合区组织为细长柱状晶和细小等轴晶。热影响区(HAZ)组织主要为板条马氏体、贝氏体和少量残余奥氏体;焊缝区主要由α-Fe,NiCrFe,Fe-Ni以及MnSi_2等相组成;焊缝区的硬度最高值约为518 HV,HAZ硬度最高值约为560 HV,从HAZ到基材硬度明显下降;焊接接头的抗拉强度平均值为802 MPa,断口均出现在靠近焊缝的母材区;焊接接头的冲击韧性为75.7 J/cm~2;焊接接头的残余应力为压应力,焊缝区的残余应力平均值为-17 MPa,热影响区的残余应力平均值为-59 MPa。
High-strength 30CrMnSiNi2A steel was welded by 5 kWCO_2 laser to obtain excellent welded joints. The microstructure, hardness and tensile strength of laser welded joints were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester, electronic universal testing machine and X-ray stress tester , Tensile fracture and residual stress were studied. The results show that the central zone of the weld is equiaxed and the dendritic structure is near the center. The marginal zone is composed of coarse columnar crystals, and the fused zone is composed of elongated columnar crystals and fine equiaxed grains. The HAZ mainly consists of lath martensite, bainite and a small amount of retained austenite. The weld zone mainly consists of α-Fe, NiCrFe, Fe-Ni and MnSi 2 phases. The weld zone hardness The highest value is about 518 HV, and the highest HAZ hardness is about 560 HV. The hardness from HAZ to base material obviously decreases. The average tensile strength of welded joints is 802 MPa, and the fracture appears in the base metal near the weld. The impact toughness of the joint is 75.7 J / cm ~ 2. The residual stress of the welded joint is compressive stress, the average residual stress of the weld zone is -17 MPa and the average residual stress of the heat affected zone is -59 MPa.