| Copper has the characteristics of high thermal conductivity and ablation resistance,while stainless steel has the characteristics of high temperature,high strength and good bearing performance.The copper steel composite heat exchanger manufactured by vacuum diffusion bonding technology can give full play to the advantages of the two materials,and provide a new type of heat exchange element for high-pressure environment.At present,there is an urgent demand for copper steel composite heat exchanger in aero-engine combustion chamber,nozzle,nuclear island cooling system and drilling platform.However,due to the difference of physical properties of the two materials,the diffusion bonding technology of copper steel still has the following bottlenecks:the difference of thermal expansion coefficient of dissimilar materials leads to the internal stress in the welding seam of structural parts during the cooling process after welding;the joint strength formed by different materials is low,which can only reach 33%of the strength of copper alloy base metal,and the joint strength needs to be greatly improved.In view of the above problems,this paper focuses on the research of diffusion bonding process parameters,welding deformation and welding rate control method of copper steel composite heat exchanger,explores the key technology,and lays a technical foundation for the manufacture and application of copper steel composite heat exchanger.In order to complete the above research,firstly,TU1 copper sample block and304 stainless steel sample block are designed.Through diffusion connection of TU1copper and stainless steel sample block,tensile sample and metallographic test sample are made.Using tensile test and metallographic detection method,the main parameters affecting diffusion bonding,such as diffusion temperature,pressure,holding time,etc.,which affect the mechanical properties and welding of welded joints,are completed The results show that the parameters have a strong influence on the process.Through the design of diffusion welding plate sample,the size inspection and cutting inspection of the sample after welding are carried out,and the factors influencing the sample deformation,surface groove and other defects in the test process are analyzed.Through the research on the manufacture and inspection of copper steel heat exchanger structural parts,the vacuum diffusion bonding process of TU1 copper-304 stainless steel was mastered,and the qualified manufacturing and inspection of typical structural parts were completed.The conclusion is that the mechanical properties of TU1 copper-304 stainless steel are the best when the diffusion connection pressure is 2MPa,the holding time is 60min,the vacuum degree is 5.0×10-3pa and the diffusion connection temperature is950℃.The research in this paper provides technical accumulation for the self-made heat exchanger with integrated structure and multiple functions,promotes the application process of copper steel composite nozzle in a certain type of Solid Ramjet,and lays a foundation for the completion of the model task. |
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