Study On Cold Welding Repair Process And Microstructure Properties Of Four Kinds Of Shaft Steels

With the continuous development of remanufacturing industry at home and abroad in recent years,the application of pulse cold welding repair technology in industrial remanufacturing has attracted more and more attention.Pulse cold welding repair technology is a kind of surface repair technology based on pulse signal,which can repair the defects of parts well.It is the key technology for repairing the unit spindle after wear.It has the advantages of economy,convenience,precision,small heat affected zone and so on,and has become an important repair technology in the remanufacturing of large shaft parts.Based on the remanufacturing theory,this thesis analyzes the types and related mechanisms of friction loss of the main shaft of the unit.In view of the surface defects existing in the repair manufacturing process of traditional welding technology and the common wear,scratches and bumps in the use of the workpiece,there are problems such as high welding heat input,large weld deformation,poor forming and low strength in the welding repair layer.In order to further improve the strength,hardness,wear resistance,binding interface composition,element diffusion,and study the tensile fracture and friction and wear mechanism of the welding repair layer of axial steel,this paper adopts high energy pulse cold welding technology to repair the surface defects of common axial steel 45#,40 Cr,3Cr13 and 17-4PH.By controlling pulse current and pulse time,the forming quality of spot welds,single pass welds,single single pass welds and multi-layer and multi-pass welds under five groups of cold welding process parameters were studied.The influence of cold welding process parameters on the macroscopic morphology,weld penetration,weld width and other geometric dimensions of spot welds and single pass welds as well as the weld forming coefficient was emphatically studied.Combined with the weld forming quality under different process parameters,the optimal process parameters were given,and then the cold welding repair layer was prepared under the optimal set of process parameters.The structure and properties of the cold welding repair layer were studied comprehensively.The mechanism of cold welding repair and the applicability of welding were revealed by studying the internal structure between the cold welding repair layer and the base metal as well as the diffusion of elements in the weld fusion zone.The microhardness changes between the repair layer and the base material were studied and compared.The heat affected zone was narrow and the hardness of the repair layer was much higher than that of the base material.The bonding strength between the repair layer and the base material was tested.The research showed that the tensile strength of the repaired object could be improved after cold welding,and the tensile strength of the repair layer was higher than that of the base material.The friction and wear properties and wear mechanism between the repair layer and the corresponding base material are studied and compared.The wear resistance of the repair layer is close to that of the base material.Based on the above related studies,this thesis provides feasibility analysis for the application of cold welding repair in the unit spindle wear,provides relevant solutions for the repair process of common shaft materials,and provides reference for the development of cold welding repair technology in the field of remanufacturing industry.