双金属复合钢管界面及焊缝的微观结构

MICROSTRUCTURE OF INTREFACE AND WELDING SEAM IN DUAL-METAL CLAD STEEL PIPE

通过金相分析、微区成份分析、宏观和微观断口分析,主要研究钎焊层和焊鏠区的微观结构及其对复合钢管工艺性能和使用性能的影响。研究结果表明,镍基钎焊层通过扩散形成界面,实现了完全的冶金结合。组成复合钢管的各层以及焊鏠金属的力学性能相近,变形均匀,保证了复合钢管的可焊性和强韧性。铜钎焊复合钢管由于高温铜脆而引发焊接裂纹,且其钎焊层硬度明显高于基层和复层,导致层间剪切及沿界面发生分层脱离,固该铜基合金不宜做复合钢管钎焊料。

A study was carried out on the microstructure of interface and welding seam in dual - metal clad steel pipe. And its inferences on technological and service properties were studied. The metallographic analyze, composition analyze of micro region and fracture surface analyze were conducted. The results show that the interface between nickel solder and steel is metallurgical joint by diffusion. The hardnesses of solder and inside layer, outside layer are near each other. These guarantee weld ability and the compound steel pipe to be tough. In the Cu - based solder steel pipe, high temperature copper brittleness occurs, and leads to intergranular crack. The hardness of solder layer is obviously higher than that of inside and outside steel layer, causing un harrffonizing deformation with each other and shear between layers. That causes interfaces to separate. So the Cu - based solder is not a good solder.