Studies On The Induction Brazing Process And Properties Of Aluminum Tube Joints In Refrigeration System

Application of aluminum tube in the refrigeration industry is limited by thedifficulty of connection. The traditional connection methods cannot meet therequirements of refrigeration system. Induction brazing uses predetermined programcomplete the connection. It is easy and reliable to operate and repeate. It is alsofriendly to the environment. Induction brazing can meet the requirements of theonline production when the inductor equipped with a flexible cable. In this paper, westudy the properties and microstructure of the aluminum tube joint by differentinduction brazing process through a variety of technical means to explore theoptimal induction brazing process and discuss the feasibility of its application inpractice.Exploring the induction brazing process firstly with adjusting the power,heating method and time. When heating rate is at less than100℃/s and holdingheating for5s can guarantee the quality of the joint. After the small batch test, detectthe appearance of the joints. The qualified rate can reach100%. Under optimalinduction brazing process, the joint is heated gently and the peak temperature wouldnot exceed the melting point of aluminum. The longer holding time can guaranteethe brazing filler spreading on the base material and the depth of the brazing line canmeet the requirements.Then take the joint properties test, the test includes mechanical and corrosionresistance test. Test results show that the joint under optimal induction brazingprocess can meet the requirements of refrigeration system.Using optical microscopy, SEM to observe the microstructure and EDS to getthe elements composition of the joint. Since the Al-Si pseudo-binary phase is closeto Si phase, and the solidification of liquid Al-Si brazing filler is fast, themicrostructure of the joints is sub-eutectic, as (Al)＋[(Al)＋(Si)]. Under theoptimal induction brazing process, one hand can avoid porosity occur, on the other hand Si can reinforced to Al in liquid Al-Si brazing filler, the content of Si declines.Coarse Si eutectic structure is refined.At last, Aluminum refrigeration system is designed and a model is produced. Itproves that aluminum refrigeration system and induction brazing process foraluminum tube is feasible.