The Application Of Transient Liquid-Phase Diffusion Bonding In Pipeline Welding

TLP is a high effective welding method whose characteristics is lowwelding temperature, infusible base material, suit to weld heterogeneitymaterial, low transformation, intension approximate to base material, goodhigh-temperature performance, low investment. Now TLP has been a preferredwelding method for welding advanced material, it also has great applicationpotential in carbon steel.In order to apply the TLP in pipeline soldering, choosing self-fluxingalloy Ni60 and Fe-Si-B amorphous foil as interlayer (according to the propertyof 16MnR). Study the microscopic structure feature and mechanics property ofthe TLP joint; the influence of the interlayer and parameters on themicroscopic structure and mechanics performance; the distribution of elementsin the joint area; the appearance of the stretch fracture; the mechanism of TLPsolder. Finally using finite element software ANSYS to simulate thetemperature field and stress field of the joint.The results indicate that when using Ni60 as interlayer, there are a lot ofcavities and foreign impurities in the joint area, the mechanics performance ofthe joint is low. The reason is the low compact of the powder Ni60. Whenusing Fe-Si-B as interlayer, the quality of the joint is good, the main defect of the joint is cavity and infusion, the welding parameters have great effect on themicrostructure, and appropriate welding parameters will reduce the weldingdefect. Through quadrature experiment, the best welding parameter istemperature 1150℃, press 6MPa, time 10min. Appearance of the stretchfracture of the joint has the character of cleavage Fracture, Dimple Ruptureand Quasi-cleavage Fracture which indicate that the joint is metallurgy joint.The main reason of the fracture is the appearance of the mechanical joint areaand microscopic gap. B distribute averagely in the joint; the concentration ofSi decline gradually from interlayer to base material; Mn convene in the joint.There are four phases in the forming of the welding interface; they are thewetting of the interlayer on the base material; the breaking of the oxide film;the diffusion between interlayer and base material and the disappearing of thecavity; the equality of the joint. The simulation of the temperature field andstress field indicate that the residual stress is generated at the cooling stage, itconcentrate in the base material near the interlayer, the tensile stress of thebase material reach the peak value at perimeter area. The using of theinterlayer can reduce the concentration of stress; improve the strength of thejoint.