Research On Welding Deformation Control Of Aluminum Alloy Vehicle Metro Underframe

Aluminum alloy of lightweight metro car body can achieve excellent structure design,beautiful appearance,resistance to corrosion resistance,light weight,good dynamic performance,because of its machining,welding performance,which is in line with the requirements of energy saving and emission reduction and is widely applied to urban rail transportation.But the large coefficient of thermal expansion of aluminum alloy,welding deformation,directly affect the appearance and dimensional accuracy of the product,thus the control of welding deformation is the key to ensure the quality of products.The underframe is an important component of aluminum alloy car body,which is mainly composed of end structure,side beam,long floor,end cover and other core accessories.The assembly deformation of aluminum alloy subframe was carried out orderly with self-restraint conditions in this study,it is found that,after welding process I and?,the shrinkage is larger in width,while it has little influence on the length and deflection of the underframe.In the process ? and ?,the influence of the welding process on the width shrikage the underframe structure is little,however,the long floor welding has the greatest impact on the deformation in length direction,as well as deflection is greater.The last process?and ? was carried out after the weldment overturn,The effect of welding process?on the width of the underframe is larger than other steps.The process ? has a great influence on the length of the bottom frame,and the bending angle of the pillar beam is the largest,about 50%.Through the analysis of the chassis structure,welding procedures and welding position,the reasonable welding sequence,the effective welding standard,the rigidity constraint of the tooling was adopt sysmetically to control the chassis welding deformation.Moreover,the chassis welding after the length and width of data measurement and analysis was carried out,and the presetting value is detected and corrected to obtain a reasonable width-corrected volume(?BZ),length-corrected volume(?LZ)and anti-deflection correction(?P2).The results show that the deformation control measurements mentioned above,can guarantee a geometric tolerance and dimensional tolerance.The techniques have been used in the actual production of aluminum chassis,which guarantes a one-time pass rate of 98%,increased production efficiency,reducing the number of rework as well as production costs.