Arc Welding Technology Of Shipbuilding Aluminum Alloy/Steel Dissimilar Metals

Nowadays,the shipbuilding industry has an increasingly demand for light-weight.Due to the advantages of low density,high specific strength and good corrosion resistance,aluminum alloys are used to replace the original steel superstructures of ships.This kind of aluminum/steel composite structure can reduce the weight of the hull and increase the speed of the ship.However,the joints produced by the aluminum/steel composite welding process using the traditional aluminum/steel structural transition joints are prone to safety hazards such as cracking of the transition joint during welding manufacturing and service.Therefore,in-depth research on aluminum/steel composite welding technology is very important,and the development of novel aluminum/steel welding technology is also urgent.In this paper,the traditional composite welding process with aluminum/steel transition joints is used to study the influence of welding heat input on the interface temperature,microstructure and morphology and mechanical properties of the aluminum/steel structural transition joints.At the same time,the TIG welding-brazing process of 5083 aluminumalloy/E36 steel conducted with Zn-22Al flux cored wire is studied.The effects of welding current and preheating temperature on the morphology,intermetallic compound changes and mechanical properties of the interface layer were discussed.Explore the feasibility of high-strength and high-efficiency aluminum/steel dissimilar metal welding-brazing technology.The aluminum/steel composite welding research shows that the heat input required to bring the aluminum/steel interface to the same temperature is much smaller on the aluminum side than on the steel side.The change of welding heat input has little effect on themacrostructure and microstructure of the joint.The microstructure of 1050 aluminumalloy/CCSD steel interface is composed of three parts,which are pure solid phase bonding zone,Fe-Al intermetallic compound layer and ripple structure composed of aluminum alloy and Fe-Al intermetallic compound.As the welding heat input increases,the temperature of the aluminum/steel interface rises,and the cracks existing in the Al-rich intermetalliccompound propagate,resulting in the shear strength of the 1050 aluminum alloy/CCSD steel interface in the explosive welding joint gradually decreasing.Research on aluminum/steel welding-brazing technology shows that the use of Zn-Al22flux-cored wire can produce aluminum/steel welding-brazing joints with good performance.Due to the good weld performance,the thinner?-Fe₂Al₅Zn_x layer on the steel side,and the?-FeZn₁₀ phase dispersed in the?-Fe₂Al₅Zn_x layer which can suppress the crack propagation,the maximum tensile strength of the joints is 120 MPa,the welding parameters of the joints are preheating temperature 150?and welding current 110 A.The fracture occurs at thebrazed interface of the steel side groove and passes through the weld along the interface.The preheating temperature mainly affects the wetting of the weld metal on the steel side,and the welding current mainly affects the melting of the aluminum alloy and the generation of pores in the weld.There are two kinds of intermetallic compounds occurred at the brazing interface of steel side:the first is the?-Fe₂Al₅Zn_x intermetallic compound layer,the thickness of which increases with the increase of the welding current;the second is the Fe-Zn intermetalliccompound,which is mainly divided into two forms,one is the?-FeZn₁₀ phase dispersed in the?-Fe₂Al₅Zn_x layer;the other is the continuous layer composed of?₁ phase and?-FeZn₁₀ phase between the steel substrate and the?-Fe₂Al₅Zn_x layer that occurs when the welding currentexceeds 120 A,both Fe-Zn intermetallic compound increases with the increase of welding current and preheating temperature.