Investigation Of Transient Liquid Phase Bonding For 12Cr1MoV/TP304H Heterogeneity Steel Pipes

In this paper, recent research of transient liquid diffusion bonding is described, and based on the successful experiences of TLP bonding experiments for same kinds of boiler steel tubes, a suitable interlayer was confirmed and the TLP bonding for two kinds of heterogeneity steel tubes, namely, the 12CrlMoV and TP304H, was successfully achieved.In the experiments, samples were heated by intermediate-frequency induction and were carried out with the protection of argon in room atmosphere. Quality of the tie-in was evaluated by room-temperature mechanic properties as well as the phase microstructure. During the experiments, the selection of the interlayer, the design of the bonding process, the ascertainment of process parameters, as well as the atom diffusion model were systematically explored. Moreover, tests of mechanic properties of the tie-in were conducted, microstructures of welding lines using different method as well as element distribution were examined by OM, SEM and EDS, there as follows:(1) Based on mechanic properties of tie-in, perfect tie-in. through experiments on different inter-layers, we concluded that TA and LG+ FeSiB are preferable materials for TLP bonding between pearlite 12CrlMoV refractory steel and austenite TP304H stainless steel.(2) According to the mechanic properties and microstructures, the optimal processparameters for tie-in bonded by pearlite 12CrlMoV refractory steel and austenite TP304Hstainless steel, were explored by orthorhombic-experiment method. The optimal parametersare as follows: with TA as interlayer, the optimal temperature, holding time and bondingpressure are 1240℃, 3min and 4MPa respectively; while with LG+FeSiB as interlayer,1230℃,3min and 4Mpa respectively.(3) During the process of transient-liquid diffusion bonding for 12CrlMoV and TP304Htubes, diffusion of the main alloy elements is asymmetric, that is, the centre-line of thewelding interface deviated the centre-line of the interlayer, and slightly shifted to the side ofTP304H tube which has high contents of alloy elements. Moreover, the magnitude of thedeviation increases with the temperature.