Study On Forming And Welding Technology Of 2A12 Aluminum Alloy Stop Valve Body

With limited global copper resources,it is imperative to select copper substitutes.Our country is rich in aluminum resources.Aluminum and its alloys have the advantages of recyclability,lightweight,excellent corrosion resistance,good mechanical properties and welding properties.Therefore,it is of great significance to carry out the research on substituting aluminum for copper.At present,the demand of household air-conditioning is increasing,and the number of copper stop valves in air-conditioning is also increasing.The selected aluminum alloy material not only has the same strength as the original lead brass material,but also has good plasticity and weldability.So the difficulty of this subject is the forming of complex parts of high strength aluminum alloy and the problem of aluminum-copper welding.In this paper,the forming process of aluminum alloy stop valve body is studied by combining finite element analysis with experiment.At the same time,the welding process of aluminum/copper dissimilar metal is studied,which provides theoretical guidance for the production of aluminum alloy stop valve.In order to obtain the material data related to 2A12 aluminum alloy in FORGE finite element software,the thermal simulation compression test of 2A12 aluminum alloy is needed first.The hot deformation behavior of 2A12 aluminum alloy was studied at deformation temperature of 350⁵00?and strain rate of 0.01s^-11s^-1.The experimental results show that the true stress of 2A12 aluminum alloy increases with the increase of strain rate and the decrease of deformation temperature.The Hansel-Spittel constitutive model for high temperature thermal-viscous flow in FORGE finite element software is also established.Secondly,the hot forging method was used to shape the aluminum alloy stop valve body,and the extrusion process was compared and studied by experiment and FORGE finite element software simulation,and the experimental process was optimized.The results show that the simulation results show that there is no sudden increase of extrusion force after extrusion,but filling is not full at the foot of the valve body,and a few defects are found at the place where the valve nozzle cap is installed at the same time.Through extrusion test,the experimental results are consistent with the numerical simulation results,and cracks appear at the place where the valve nozzle cap is installed,but in appearance.The forming quality of aluminum alloy stop valve is better,which is related to the forming fluidity of 2A12 aluminum alloy.By improving the process,the fillet of the foot of the valve body was increased from 2 mm to 2.5 mm,and the forming temperature of 2A12 aluminum alloy was appropriately increased to 455?,which effectively improved the formability of the aluminum alloy valve body.Finally,brazing experiments of aluminum valve body/copper pipe in heterogeneous metal furnace were carried out.Al-Si-Zn-Cu-Sn brazing filler metal was selected to conduct welding experiments at different temperatures.The experimental results show that the ideal welding temperature range is 560⁵80?,and it has good air tightness in high and low pressure environments.From the microscopic structure,the metal compounds at the interface of brazing filler metal at 560?and 570?are very thin,ranging from 6 to 7?m and 4 to 5?m.The central zone of the weld is mainly composed of solid solution and eutectic structure,and no compounds are found.Below this temperature range,the solder does not melt and aggregate,and above this temperature range,the solder is corroded.According to the thickness of the compound layer,570?is more conducive to the brazing of the filler metal in the furnace.