Aluminum is used as a primary material in various industries due to its light weight, excellent formability, corrosion resistance, and thermal and electrical conductivity.Among these applications, heat exchangers, which constitute a core market within the aluminum industry, utilize brazing.In aluminum brazing, flux is used to remove the strong oxide layer.However, using flux has drawbacks: it pollutes the work environment, requires cleaning flux residues after brazing, is economically and time inefficient, and the flux itself is expensive.Furthermore, while brazing with non-corrosive flux has the advantage of eliminating the need to clean off the flux, it has the disadvantage that flux residues make it unsuitable for precision components and food-related applications.Consequently, flux-free brazing is sought.Recent reports describe flux-free brazing techniques utilizing either fracture caused by the thermal expansion coefficient difference between the base metal and oxide layer during rapid heating, or the reduction reaction of Mg in Al alloys by the oxide layer.This study aimed to evaluate the effect of heating rate on flux-free brazing using tensile tests and Xray CT inspection, seeking brazing conditions yielding high tensile strength.The results revealed that tensile strength correlates with the area where interfacial reactions occur, confirmed an increase in tensile strength due to rapid heating, and clarified that achieving a larger area of interfacial reaction requires high precision in the joint surface, specimen placement, and brazing atmosphere.
SAITO et al. (Thu,) studied this question.