Research Of Separating Technical To Cu-Al Brazing Joints

Copper to aluminum joints are widely used in petrochemical industry,electrical and electronic industry and refrigeration industry of which have a wide range of applications,and also have a wide application prospects.In this passage,Cu-Al joints have been carried out by vacuum brazing technology using an Al-Si filler metal of ER4047,the phase change in brazing process has been studied by means of metallography,electron probe microanalyser (EPMA)and X-ray diffraction(XRD),process parameters and brazing seam region organization of copper to aluminum brazing joints has been discussed from proliferation of elements,formation of solid solution and intermetallic compound,etc.Experimental results obtained showed that the proper technology parameters are:brazing seam gap 0.10mm, brazing temperature 600℃,and vacuum level 10^-2Pa,while heating rate 15℃/min.The interface of Cu to Al brazing includes a transition region on Cu side,middle brazing seam region and a transition region on Al side at that time.Layers of Cu₃Al₂ and CuAl₂ are formed between the brazing seam and the Cu substrate.Average width of layered Cu₃Al₂ is about 12 mm,and CuAl₂ is about 8 mm.XRD results indicated that the brazing seam region is mainly consisted ofα-Al solid solution,Cu₃Al₂ and CuAl₂ IMCs.Moreover,ε-Cu₁₅Si₄ phase,Al-Si phase and CuZn₂ phase are formed,and these phases appear in the form of acicular compounds.In the brazing seam region,α-(Al)+CuAl₂ binary eutectic phase is formed.Starting from the basic idea of remanufacture,we studied separation methods of copper to aluminum brazing joints,because of a simple principle,easy to operate,and relatively simple equipment we used smechanical isolation and heat separation to isolate copper to aluminum brazing joints,the main experimental results obtained showed that the welding joints of Cu to Al joints from the refrigerator is smooth,who has a pleasing appearance and the deformation of which is small,we found that there is no obvious defects visible,microstructure analysis and EPMA analysis showed that the welding seam of Cu to Al Fridge Condenser Brazed Joints contacted good,there is no obvious defects also,so we condensered that the copper to aluminum brazing joints have a good quality,relatively;At the same time,we can see that the brazing seam of Cu to Al joints from the abandoned refrigerator is wider than that from unused refrigerator,we condensered that is due to the localized corrosion in the using process. Tensile test results of Cu to Al brazed joints from refrigerator condenser showed that the average tensile strength of these joints is more than 98MPa which can fully meet the requirements of Guangdong enterprise standards.However,due to the good shaping abilty of Cu and Al and the small wall thickness of this Cu to Al Fridge Condenser Brazed Joint and whose intensity is relatively high,the base materials occured a serious deformation during the mechanical separating process.Also,the fault location is not precisely occurred in the filler metal joints of the department but is more oriented toward the side of Al base metal;therefore, the mechanical separation of the Cu to Al Fridge Condenser brazing joints does not have the actual operation.As a result of filler metal materials dissolved well into the base material in the brazing process,the filler metal can not completely remove from the base material even separation in a heating temperature of 580℃,at the same time,because of repeated heating in process of brazing and separation that caused serious deformation of materials,especially Al material,we used a lot of heating energy in the process of thermal separation also which is not economic.Therefore,thermal isolation does not have actual operation in separating this Cu to Al brazed joint.Due to mechanical separation and thermal separation method are both not suitable for separation of this Cu to Al brazing joints,we tried electrolysis method to separating Cu to Al brazing joints.Main experimental results obtained showed that through anodic polarization curve experiment in experimental electrolytic electrolyte we know that Cu to Al brazed joints has different electrode potential in different parts,therefore,electrolysis separating method can be used for separating of this Cu to Al brazed joints.Experimental results showed that too low electrode voltages will cause to serious loss of aluminum as anodes while too high electrode voltages is vulnerable to heat and blown the copper wire,both are not in favor of the electrolysis separating process.So in this study we experimented the electrode voltages between 0.5V to 1.0V that we discussed the relationship between power time and quality losing to the electrode voltages under different electrode voltage;in the same circumstances of electrolyte concentration and PH,both power time and quality losing rate decreased along with the increase of electrode voltages;while the electrode voltages is 0.8 V or electrode voltages is 0.9 V,the power time is short and quality losing is small and in the process of electrolysis separating,there is no wire broking,therefore,these are more satisfactory parameters of the separation process.At the end,we determined the concentration of Al³⁺ from electrolytic electrolyte after the separation using IRIS Advantage ER/S sequential plasma emission spectrometer from the USA,we also calculated that the quality of Al³⁺in solution can corresponding well with data of quality losing in the procedure of electrolysis separation thus proofed that the quality losing of copper-aluminum brazing joints in procedure of electrolysis separation is mainly coming from aluminum which is used as Anodes.