大截面变化率汽车排气管的多工步液力成形工艺

Multi-step hydro-mechanical forming process for automobile exhaust pipe with large changing rate of cross section

为解决某乘用车大截面变化率排气管的整体制造难题,以439铁素体不锈钢管作为研究对象,基于eta/DYNAFORM建立了包含合模、补料、成形、整形在内的液力成形过程的有限元模型。并与实验相结合,研究了关键工艺参数对成形质量的影响规律,设计并优化了液力成形加载路径。结果表明,加载路径对排气管的壁厚分布和减薄率有显著影响。第1道次下,经响应面法优化后得到了成形压力、整形压力、轴向补料位移所组成的加载路径,所得到的零件最大减薄率为15.3%。第2道次下,优化后的最大减薄率为5.0%。第3道次下,优化后的最大减薄率为5.2%,以上3道次优化前的累计最大减薄率为31.5%,优化后的累计最大减薄率为23.7%,降低幅度为24.7%。最终通过实验验证证实优化后的液力成形工艺显著降低了零件成形开裂风险,并获得了质量优异的大截面变化率整体汽车排气管零件。

In order to solve the overall manufacturing problem of exhaust pipe with large changing rate of cross section for a passenger car,the finite element model of the hydro-mechanical forming process including die closing,feeding,forming and shaping for 439 ferritic stainless steel tube was established based on eta/DYNAFORM.Combined with experiments,the influence laws of key process parameters on forming quality were studied,and the loading path of hydro-mechanical forming were designed and optimized.The results show that the loading path has a significant effect on the wall thickness distribution and thinning rate of exhaust pipe.In the first pass,the loading path including forming pressure,shaping pressure and axial feeding displacement is obtained by the response surface method,and the maximum thinning rate of the obtained parts is 5.2%.In the second pass,the maximum thinning rate is 5.0%after optimization.In the third pass,the maximum thinning rate is 5.2%after optimization.The cumulative maximum thinning rates before and after optimization are 31.5%and 23.7%,the reduction region is 24.7%.Then the experimental verification proves that the optimized hydro-mechanical forming process significantly reduces the risk of crack for part,and the excellent overall automobile exhaust pipe parts with large changing rate of cross section are obtained.