设计了窄间隙的坡口并采用CO2 激光填丝多道焊的方法焊接了厚度为50 mm 的30Cr2Ni4MoV 转子钢，焊后观察并分析了接头不同区域的组织特征，通过接头的拉伸、弯曲试验及显微硬度评定了接头的性能，结果表明：选取优化的窄间隙激光填丝焊接工艺焊接的50 mm 厚30Cr2Ni4MoV 钢对接焊接头成形良好，无侧壁未熔合等缺陷。接头中部填充焊焊缝中心由大量的针状铁素体和少量的粒状贝氏体组成，冲击韧性良好，表层填充焊焊缝由马氏体及少量的粒状贝氏体组成，冲击韧性有所下降。焊接接头拉伸试样均断于母材，接头最大硬度位于接头表层填充焊热影响区(HAZ)粗晶区，焊缝区的硬度较HAZ低很多。

A type of groove targeted on ultra- narrow- gap multi- pass welding is designed and 50 mm thick 30Cr2Ni4MoV turbine rotor steel is welded by CO2 laser welding with filler wire based on the groove. After welding process, the microstructures of different zones of joint are observed and analyzed. The tensile test, bending test and measurement of microhardness are conducted to evaluate the properties of joint. The results show that the joint of 50 mm thick 30Cr2Ni4MoV turbine rotor steel has fine appearance without defect under the optimized parameters of ultra- narrow- gap multi- pass laser welding with filler wire. The middle zone of weld consists of a mass of acicular ferrite and a few of granular bainite and it shows good impact toughness. The surface layer of weld consists of martensite and a few of granular bainite and its impact toughness decreases a little. The fractures occurre on the base metal of tensile test specimens. The peak value of microhardness is achieved in the coarse grain zone in heat affected zone (HAZ) of surface layer of weld and the microhardness in weld is much lower than that in HAZ.