Transient liquid phase bonding of 45MnMoB steel geological drill pipe using two-step heating process

The geological drill pipe (45MnMoB steel)was joined by transient liquid phase bonding with a novel two-step heating process.The mechanical properties and microstructures of the joint were investigated, and compared with those of the joint produced by the conventional heating process.The results showed that both the heating processes produced a homogenous joint with microstructure and composition equivalent to the base metal.Compared with the conventional one-step heating process, the two-step heating process (1 250℃, 1 min and 1 230℃, 2 min)remove the dissimilar interfaces, and increased the bonded ratio, and get the joint with tensile strength of 890 MPa and bending degree of 180°, which exceeded the technical criterions of geological drill pipe.As this technology can be applied in drill pipe production without postweld machining process, and the production costs will be reduced.