Study On Back Pressure Forming Process Optimization Of Variable Wall Thickness Fixed Scroll

The scroll is the core component of scroll compressor for vehicle,which can be divided into the orbiting scroll and the fixed scroll.In order to meet the requirement of high efficiency and energy saving,the shape of the fixed scroll is becoming more and more complex and difficult to form.The existing forming process can not fullfil the production requirements,and defects such as underfilling,folding,mold breakage are often encountered in production.Thus,a new type of variable wall thickness fixed scroll was chosen as the research object in this paper takes,the finite element numerical analysis technique was combined with various optimization methods to analyze the forming process of variable wall thickness fixed scroll,and the influence of various process parameters on the forming quality was studied.The existing back pressure forming process was optimized and verified by experiments.The main research contents and conclusions of this paper are as follows:Based on the shape characteristics and forming accuracy of the fixed scroll,the forging diagram was designed.Design scheme of complete set of molds for variable wall thickness fixed scroll was put forward according to the preliminary forming process and the key points of the mold design,and the back pressure mould frame was developed.The common defects in the process of back pressure forming of the new type of thick wall constant scroll are summarized.The model was refactored based on the rigid-plastic finite element method and DEFORM-3D is used to invert the process of forming defects(underfilling,bottom die fracture).The generative mechanism of defects were analyzed from the angle of metal flow law and mold deformation.According to the analysis results,the original forming scheme and mold design were improved and verified by simulation experiments.According to the characteristics of the product,the forming quality evaluation indexes of the variable wall thickness fixed scroll are put forward as forming load,height difference and end face flatness.The influence of process parameters(forming temperature,mold temperature,back pressure,back pressure distance)on the back-pressure forming quality of the variable wall thickness fixed scroll were studied by orthogonal experiment.The mapping relationship between process parameters and forming quality evaluation indexes is established by the fuzzy comprehensive evaluation method and numerical fitting.According to this,the optimal combination of process parameters for variable wall thickness fixed scroll back pressure forming was determined: The billet temperature was 460 ?,the mold temperature was 240 ?,the back pressure was 9.3077 t,and the back pressure distance was 6 mm.The improved back pressure forming process scheme was verified by the process test.Theresults show that the obtained parts are well formed and the end face quality is good.After the mold works for 12000 times,no fracture was observed at the end of the die vortex.The height difference of the outer wall and the vortex of the fixed scroll forging is not more than 0.6mm.The microstructure is white ? solid solution + gray dot eutectic silicon,and the distribution of silicon particles is relatively uniform,no burnt structure is seen.The hardness of the fixed scroll is between 127 and 135 HB,and all the indexes of the tensile test reached the technical requirements of the fixed scroll.