Research On Magnetic Pusle Joining Of 3A21 Aluminum-20 Steel Tubes With Field Shaper Assisted Coil

Magnetic pulse joining of dissmilar tubes based on electromagnetic forming principle is a fast, clean and"cold"solid-state processing approach. With appropriate impact velocity and angle, a tiny-micro metallurgical bond can be achieved on the interface of the two workpieces. Field shaper is a main part of the electromagnetic joining, which has an important effect on magnetic field distribution and coil life. Main parameters affecting magnetic pulse joining process with a field shaper through numerical simulation and experiments have been studied in this thesis.The influence of field shaper's cone angle to inductant working currents has been acquired: the inductance grows as the slope angle increases, leading to the proportional growth of the relative value of the working current and the field-shaper's efficiency. 3D simulation by software ANSOFT has been established to study the magnetic field distribution and it concludes that the magnetic field of the coil with field shaper is obviously stronger than that of the coil alone when forming the same tube. This principle is the rigid standarlization of choosing right field shapers.FEM softwares ANSYS and ABAQUS have been used to carry out numerical simulation of the impact process, other processing parameters'effects on magnetic field and deformation zone have been analyzed as well . ANSYS has been used to draw the magnetic field contour and trace the acts of Lorentz force on the flyer tube. The impact velocity is obtained from the simulation model set by Abaqus. The serial numerical results showed that the impact process finished already in the former half period of dicharging, the impact velocity increased with the growth of discharging voltage and the workpiece gap. The maximum impact velocity of taper-joint could achieve 514 m/s.According to experimental studies on magnetic pulse joining for pre-annealed 3A21 aluminum-20 steel tubes with the coil with a field shaper, skin effect and the influence of the main parameters has been investigated. The joint quality was verified based on tensile test, torsion test, peel test and scanning electron microscopy. The welded joint can be achieved under the conditon of discharge voltage 15 kV and the slope angle(3°,4°,5°) with 20 mm long.From the analysis of joints'micro structure by metallographic and electron microscopic methods, the joint zone is made up of interface and trasition zone .All welded interfaces showed a typical microwavy pattern, with distincitve elements diffusion on both sides. The micro-hardness of the trasition zone is higher than that of the raw materials and an intermetallic compound with a similar composition of FeAl3 from Al-Fe phase diagram is detected.