2004 年 22 巻 1 号 p. 61-68
Hyper interfacial bonding process was developed as a new conceptual joining process for ultra fine-grained steels. This process is characterized by sequential bonding procedures, namely, the extremely rapid heating of surface by high frequency induction heating, removing the heating coil rapidly and pressure joining by applied stress. The average grain size of ultra fine-grained steel used was 1.50 μm. The width of HAZ in hyper interfacial bonded joint was approximately 3.5 mm. Bainite, ferrite and pearlite were formed in the higher temperature region of HAZ, and M-A constituents were formed in the lower temperature region of HAZ. Grain size adjacent to the bonding interface had grown to approximately 16 μm, and the maximum hardness of joint was about Hv250. Tensile strength of joint was 558 MPa at the heating time of 0.17 s. The elongation and the reduction area of joint were comparable to those of the base metal when the upset length was more than 0.1 mm.