Research On TIG Welding Process Of Stainless Steel/Copper Dissimilar Metal Joint Based On Spray Modification

The stainless steel/copper dissimilar metal structure is widely used in key equipment structural parts such as refrigeration and heat exchange due to its excellent corrosion resistance,good mechanical properties and high thermal conductivity of copper.TIG welding is one of the main connection methods of stainless steel and copper dissimilar metal components in the industry.Due to the large difference in physical properties between stainless steel and copper,especially in terms of thermal physical properties,it is difficult to weld the two,and the joints are easy to form after welding.Copper,hot cracks and other organizational defects affect the stable and safe application of copper and stainless steel dissimilar joint structures.In order to improve the mechanical properties of the copper/stainless steel heterogeneous structure and weaken or even eliminate the joint defects such as copper penetration and thermal cracking,this paper proposes a copper-nickel thermal spray modified stainless steel/copper TIG welding method,that is,by adding nickel metal to form copper-nickel thermal spray Layer,based on the excellent element solid solubility of nickel and high-temperature metal properties,nickel is used to reduce the copper infiltration cracks caused by the difference in linear expansion coefficient of copper/stainless steel and the element low-melting eutectic and grain boundary segregation,resulting in better performance copper/ Stainless steel dissimilar metal components.This topic explores the process characteristics and technical advantages of this method in depth,combined with the thermal spray simulation model to optimize the thermal spray process parameters,a well-formed thermal spray modified stainless steel joint is obtained,indicating that the plasma thermal spray method can be used to modify the surface of stainless steel,and then obtain Copper-nickel thermal spray modified stainless steel without obvious defects.In this paper,the macromicrostructure and mechanical properties of different copper-nickel modified joints in thermal spray modified TIG welding method are systematically studied.The results show that copper-nickel thermal spray coating can significantly improve the intergranular copper infiltration defects in copper and stainless steel dissimilar metal joints.By adjusting the proportion of copper and nickel in the thermal spray modified layer,a nickel-rich barrier area is formed at the fusion interface,which significantly reduces the expansion range of intergranular copper infiltration defects of the joint and further reduces the copper infiltration in TIG lap welding.Based on the thermal spray modified stainless steel/copper TIG lap method,by adjusting the ratio of copper-nickel thermal spray metal and process parameters,the microstructure and macro performance of the joint can be significantly improved,and a copper/stainless steel lap joint without significant intergranular copper infiltration defects can be obtained.