转向架关键部件低热输入增材修复工艺研究

An additive repairing process with low heat input for key bogie components

为优选转向架金属部件局部增材修复用的补焊工艺,文章将电火花沉积、火焰钎焊和脉冲冷焊3种低热输入焊接工艺用于40Cr钢的局部焊补,通过微观组织观察、硬度分布测试、弯曲和剪切性能测试评估补焊层的结合强度,并通过焊后工件的变形量和热影响区拉伸性能评判补焊工艺对工件的整体影响程度。结果表明:电火花沉积工艺的连接强度难以满足转向架部件的使用要求,不适用于转向架部件的局部缺陷修复;火焰钎焊以黄铜焊丝作为钎料时,连接界面存在脆性的Fe-Si界面反应层,致使连接强度降低。此外,火焰钎焊虽然加热温度低,但加热时间长,形成较宽的热影响区,不仅试件变形较大,而且热影响区的抗拉强度比母材下降20%,也不适用于转向架关键部件进行局部增材修复。脉冲冷焊工艺具有结合强度高、热影响区窄、对母材性能影响小及焊后工件变形小等优点,并且所需焊材方便生产现场就地取材,工艺过程简单,是3种备选工艺中最适合于对转向架关键金属部件进行局部增材修复的工艺方法。

In order to optimize the repair welding process for local additive repair of metal components on bogies,three low heat-input welding processes,namely electric spark deposition,flame brazing,and pulse cold welding,are used for local welding repair of 40Cr steel.The bonding strength of the repair welding layer is evaluated through microstructure observation,hardness distribution test,bending and shear performance test,and the overall impact of the repair welding process on the workpiece is evaluated based on the deformation of the welded workpiece and the tensile performance of the heat affected zone.The study indicates that the joining strength out of the electric spark deposition process is difficult to meet the operation requirements on bogie components,and therefore is not suitable for repairing local defects in bogie components;when brass wire is used as filler metal in flame brazing,there is a brittle Fe-Si interface reaction layer at the joining interface,resulting in a decrease in the connection strength.In addition,although the heating temperature in flame brazing process is low,the heating time is long,forming a wider heat affected zone,not only does the specimen deform significantly,but the tensile strength of the heat affected zone decreases by 20%compared to the base material,therefore disenabling the application of this process to local additive repair of key components on bogies.The pulse cold welding process is characterized by high bonding strength,narrow heat affected zone,little impact on the performance of the base material,and small postweld deformation of the workpiece.Moreover,the required welding materials are conveniently available for on-site production,and the process is simple,it is the most suitable process method for local additive repair of key metal parts on bogies among the three alternative processes.