采用5 kWCO2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MnSi2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/cm2; 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。

To obtain excellent welding joint, ultra-high strength steel 30CrMnSiNi2A was welded by laser. Microstructure, properties, tensile strength, tensile fracture and residual stress were investigated by means of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness testing machine,electronic universal testing machine and X-ray stress analyzer. The experimental results indicate that microstructure of central welding zone, near central zone and edge zone is equiaxed crystal, dendrite crystal and rough cylindrical crystal, respectively. Microstructure of fusion zone is fine cylindrical and equiaxed crystal. Microstructure of heat-affect zone (HAZ) is mainly lath martensite, bainite and residual austenite. The phases of welding zone is mainly comprised of α-Fe, NiCrFe, Fe-Ni and MnSi2.The highest hardness value of welding zone is 518 HV, the highest value hardness of HAZ is 560 HV. The hardness decreases significantly from HAZ to substrate. The average tensile strength of welding joints is approximately 802 MPa. The fracture appears in substrate near welding zone. The impact toughness of weld joints is 75.7 J/cm2. The residual stress of welded joints is the compressive stress. The average residual stress of weld zone is -17 MPa, and average residual stress of HAZ is -59 MPa.