|
The liquid storage tank is a core component of the receiver drier in the automotiveair conditioning systems, its quality, especially air tightness directly impact on airconditioning cooling performance. Choosing the cold-rolled3A21aluminum alloy tubeas raw material, one of the main processing is the welding of the tank cylinder with theend cap. Aluminum alloy due to the characteristics of strong oxidizing, big thermalconductivity and expansion coefficient, after welding, is easy to produce pores, hotcracks, internal stress and deformation defects and so on. So, the welding quality is noteasy to control, using low heat input, high deposition efficiency pulsed MIG welding toweld. For the pulse MIG welding controlled by many parameters, Complete analysis ofthe experimental would be take heavy workload, high cost,but with low efficiency.Therefore, for the efficient, economic, scientific optimizing the welding parameters,effectively reducing the number of experiments, doing orthogonal experiments andnumerical simulation analysis, which including evaluating quality on the welding jointsappearance, analyzing welding joints microstructure, residual stress and strain, haveimportant practical significance for produce.In this paper, choosing the welding current, welding speed, arc characteristics, thewire stem elongation and shielding gas flow as variables, five factors and four levels oforthogonal experiment was designed. Rating by scoring principles of welds formation tojoints, and then, through direct analysis to the score results, comparing various factorsrange. Sorting the factors significant in descending order as follows: welding speed,welding current, arc characteristics, the gas flow and wire stem elongation, with this, theoptimal combination obtained.0#,6#,7#,2#,15#five experimental group weldmacro-morphology, microstructure, heat cracks, porosity and microhardness distributionwere compared, and analyzed the reasons for the defects which provide a reference tooptimize the parameters.The combination of numerical simulation theory and welding the actual, reservoircylinder with end caps welded structure simplified, established grid model by usingVisual Mesh software. According to the factors significant level, established thenumerical simulation program, and setted up the heat source model, constraints, andsolution parameters. Simulation with current110A and voltage21.5V, obtained thewelding field evolution process and the welding thermal cycle curve in the welds and the welded area inside and outside at different angle, and then, analyzed the temperaturedistribution law. For another, two sets of thermal cycling curves were measured bythermocouple thermometer. Comparing with the simulation results showed the twobasically consistent, which proved the reliability of the results of the simulation.Through the thermo-mechanical coupled, the simulation was done on stress anddeformation of each program, which based on the welding-thermal-plastic finiteelement analysis theory, taking into account nonlinear material properties withtemperature change and strain hardening. Then welding residual stress fields and thewelding deformation simulation results were given and analyzed quantitatively.Finally,200parts were welding with the optimized parameter. Quality inspectionpass rate was96%. So, the optimized parameters can be used as the optimum processparameters for production.
|