Effect of Impact Velocity on Interface Characteristics of HT-9 Steel Joints Fabricated by Magnetic Pulse Welding

The weldability window in magnetic pulse welding (MPW) is proposed for the end-closure joining of HT-9 steel tubular workpieces. Based on both theoretical and experimental investigations, the impact velocity of the flyer tube at the moment of collision had a dominant effect on the bonding characteristics of the resultant joints and the optimal impact velocity was estimated to be in the range of 265–290 m/s in this alloy system. Under the optimal process conditions, no leak was detected during helium leak testing. Moreover, the integrity of the joint interface was preserved until the tube section ruptured during internal pressure burst testing. For HT-9 steel, the ductile δ-ferrite phase produced by the localized interfacial melting during MPW acted as an effective obstacle to crack propagation, thereby enhancing the fracture resistance of the joint interface. All of the results demonstrated the high integrity and durability of the HT-9 steel tube assembly fabricated by the MPW process.