Research On Welding Technology And Mechanism Of Marine Aluminum/Steel Dissimilar Metal Composite Joint

With the diversification of ship equipment and the modern development of the ship manufacturing industry,in order to achieve further improvement in ship performance,light alloys are used instead of steel as materials for superstructures or non-supporting structural parts to reduce the quality of ships,lower the center of gravity,and improve stability.Aluminum alloy is given priority as an alternative to steel due to its superior physical properties and commonality.However,due to the difference in physical and chemical properties between aluminum and steel,it is difficult to achieve reliable connection by direct fusion welding in traditional methods.Although the explosive welding method has reliable joint performance,its cost is too high.Therefore,realizing the economical and reliable connection of aluminum/steel is of great significance to the shipbuilding industry to improve ship performance.Aiming at the reliable connection of aluminum/steel dissimilar metals,a new form of transition joint was proposed.The bypass current MIG arc welding process is used to overlay a layer of aluminum alloy on the galvanized steel plate,and then the friction stir welding process is used to connect the aluminum alloy plate and the aluminum alloy cladding layer together in the form of overlap,and finally aluminum-Aluminum-steel three-layer composite transition joint.The new process method was tested to obtain transition joints under different parameters,and the mechanical properties were tested to explore the main factors and influence rules affecting the strength of the joint,analyze the composition of the interface layer of the joint,and study the compound distribution and countermeasures.The influence of joint performance verifies the feasibility of the process method and provides theoretical support for the process.Through the test,a well-formed composite joint was obtained.The tensile performance of the joint was tested.A ductile fracture occurred at the base material,and the tensile strength of the joint exceeded that of the base material.In addition to the fracture at the base material,HOOK defect fracture,aluminum/steel interface layer fracture,and aluminum/aluminum interface layer fracture occurred.These are undesirable results caused by defects in the welding process.The XRD analysis of the fracture of the aluminum/steel interface layer shows that the Fe Al,Fe₂Al₃,and Fe₃Al produced are mainly Al-Fe brittle compounds,which are the main reasons for reducing the joint toughness.Through the research of the joint welding process method,the feasibility of the aluminum/steel composite joint can be verified by the process method,and a composite joint with excellent performance is obtained,which provides theoretical guidance and technical support for the realization of production applications.