汽车内凹形管梁热成形工艺

Hot forming technology of inner concave tube beam for automobile

提出一种结合气体胀形的内凹形管梁热成形方法。首先根据内凹形管梁结构特征给出其相应分析难点;其次考虑到管梁内部无机械支撑时易发生咬边和圆角无法与模具贴合的缺陷,在合模前向管坯内部充入气体,对其进行辅助支撑,保证分形面的管坯充分流入凹模形腔;将咬边宽度、圆角贴合间隙以及最大减薄率作为评价指标,并在模具闭合行程-内压力平面上构建3种指标的等值线图,依据等值线图的分布确定最佳的模具行程与内压力组合;最后,对不同气体压力下的管梁成形后的马氏体含量、维氏硬度以及晶粒度进行分析,并通过试验对该管梁热成形方法进行验证。结果表明:管梁内部气体压力为8 MPa时,管梁的成形性最好。

For the inner concave tube beam,a hot forming method combining with gas bulging was proposed.Firstly,according to the structural features of the inner concave tube beam,the corresponding analysis difficulties were given.Secondly,considering the defects produced by the undercut and not fit the die at the rounded corners when there was no mechanical support inside the tube beam,the inside of the tube blank was filled with gas before the die clamping,and the auxiliary support was supported to ensure that the tube blank of the fractal surface fully flowed into the concave cavity.Then,the width of undercut edge,fillet fit gap and maximum thinning rate were taken as evaluation indexes,and the contour maps of three indexes were constructed on the closed stroke-internal pressure plane of the die.Furthermore,the optimum combination of stroke and internal pressure for the die was determined according to the distribution of contour maps.Finally,martensite content,Vickers hardness and grain size after the tube forming under the different gas pressures were analyzed,and the forming method proposed for the tube beam was verified by experiments.The result shows that the forming quality is the best when the gas pressure is 8 MPa.