先进高强钢边部变形能力影响因素分析

Analysis on Influencing Factors of Edge Deformation Ability of Advanced High Strength Steel

板材冲压工艺多种多样,并且其变形过程极其复杂。许多比较典型的冲压件是在几何约束下进行变形的,主要以局部成形失效为主,裂纹出现在凸缘拉伸、翻孔以及弯曲等局部的集中变形区域,无明显的减薄,也无法检测到颈缩的起始点,表现为类似的脆性断裂失效,因此采用传统的拉伸检测方法无法对该过程进行有效表征。鉴于此,为更好地探究先进高强钢边部变形能力的影响因素,选择不同牌号、不同厚度的先进高强钢进行扩孔试验。试验结果表明:随着强度提高,扩孔率呈现下降趋势;通过对不同材料进行扩孔率分析,近似厚度下三种材料边部变形能力大小为HC340LA>HC340/590DP>HC420/780DP;通过对相同钢种不同厚度扩孔率对比发现,相同钢种边部变形能力随着厚度的增加而逐渐降低;屈强比越大,扩孔率越高,小的屈强比更易造成边部的开裂。

Sheet stamping process is varied,and there is no lack of extremely complex deformation process.Many typical stamping parts are deformed under geometric constraints,and local forming failure is the main problem.Cracks appear in the local concentrated deformation areas such as flange stretching,hole turning and bending.There is no obvious thinning and the starting point of neck shrinkage can’t be detected,showing similar brittle fracture failure.Therefore,traditional tensile detection methods cannot be used to effectively characterize this process.In order to better explore the influence factors of edge deformation ability of advanced high strength steel,different grades of advanced high strength steel with different thickness were selected for the reaming test.The results are as follows.With the increase of strength,the porosity ratio decreases.Through the analysis of the reaming rate of different materials,the edge deformation capacity of the three materials under the approximate thickness is HC340LA>HC340/590DP>HC420/780DP.By comparing the reaming ratio of the same steel with different thicknesses,it is found that the deformation ability of the edge of the same steel decreases gradually with the increase of the thickness.The larger the bending ratio,the higher the porosity expansion rate,and the smaller the bending ratio is more likely to cause the edge cracking.