Porthole extrusion process design for magnesium alloy bumper back beam
Porthole extrusion process design for magnesium alloy bumper back beam
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DOI：
10.1007/s12541-015-0187-x
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发表时间：
2015-06
影响因子：
1.9
通讯作者：
I. Lee;Sung-Yun Lee;Sang-Kon Lee;M. Jeong;Da Hye Kim;Jaewook Lee;Yong-Jae Cho
中科院分区：
文献类型：
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作者：
I. Lee;Sung-Yun Lee;Sang-Kon Lee;M. Jeong;Da Hye Kim;Jaewook Lee;Yong-Jae Cho
分流挤压是制造复杂截面形状的轻质材料的一种有效工艺。在分流挤压过程中，由于模具结构复杂，物料流动复杂。因此，要设计出合适的挤压工艺并非易事。镁合金具有六方密排晶体结构，在200℃以下具有较低的变形能力。在400°C以上的温度下，它还存在表面氧化的问题。因此，设置适当的挤压条件非常重要。本研究设计了汽车保险杠后梁的分流挤压工艺。通过有限元分析，研究了坯料初始温度、拉坯速度和氮气冷却制度对挤压镁合金表面温度的影响。首先，通过挤压试验确定了表面氧化的起始温度。然后，在有限元分析的基础上，得到了考虑表面氧化温度和挤出机容量的挤压极限图。通过CFD和有限元耦合分析，研究了氮气冷却对表面温度的影响。根据分析结果和挤压极限图，确定了坯料初始温度和拉坯速度。最后，通过实验验证了所设计的挤压工艺的有效性。
Porthole extrusion is a useful process for manufacturing lightweight materials with complex cross-sectional shape. In porthole extrusion, the material flow is complex due to the complex structure of the die. Therefore, it is not easy to design an appropriate extrusion process. Magnesium alloy exhibits low deformability at temperatures below 200°C because of its hexagonal close-packed crystal structure. It also suffers from the problem of surface oxidation at temperatures above 400°C. Therefore, it is important to set the appropriate extrusion conditions. In this study, the porthole extrusion process for manufacturing automobile bumper back beams is designed. The influence of initial billet temperature, ram velocity, and nitrogen cooling system on the surface temperature of extruded magnesium alloy is investigated using FE analysis. First, the initiation temperature of surface oxidation is evaluated through extrusion test. Then, based on the FE analysis, the extrusion limit diagram is obtained considering the surface oxidation temperature and the extruder capacity. The effect of nitrogen cooling on surface temperature is investigated through coupled CFD and FE analysis. From the analyzed results and extrusion limit diagram, the initial billet temperature and ram velocity are determined. Finally, the effectiveness of the designed extrusion process is verified through an experiment.