Increasing the Lightweight Potential of Composite Cold Forging by Utilizing Magnesium and Granular Cores
Increasing the Lightweight Potential of Composite Cold Forging by Utilizing Magnesium and Granular Cores
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DOI：
10.3390/met11010032
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发表时间：
2021-01-01
期刊：
影响因子：
2.9
通讯作者：
Tekkaya, A. Erman
中科院分区：
文献类型：
--
作者：
Gitschel, Robin;Kolpak, Felix;Tekkaya, A. Erman
本文介绍了一种用C15钢杯形冷锻坯料正挤压棒材生产轻质轴的工艺流程。钢杯坯的特点是轻质镁合金芯或粒状介质芯，在成型后将其去除，以获得空心轴，而无需复杂的工具和高负载的心轴。结果表明，具有镁芯的复合轴可以产生广泛的挤压应变。由于棒形件正挤压时的高流体压力，镁合金的室温成形极限可以得到扩展。观察到的芯和鞘之间的结合强度低于所使用的镁AZ 31合金的剪切屈服强度。采用氧化锆微珠或石英砂作为失芯，成功地生产了空心轴。针对可压缩颗粒介质破坏金属塑性成形中的定容定律的问题，采用修正的Drucker-Prager屈服面对这些材料进行了模拟，为有效的工艺设计提供了一种工具。颗粒芯和镁合金芯为通过复合冷锻生产轻质轴提供了新的可能性。这两种工艺变体都比基于铝芯的复合轴节省了更多的重量。
In this paper a process sequence, that uses forward rod extrusion with cold forged C15 steel cup billets to produce lightweight shafts, is presented. The steel cup billets feature either a lightweight magnesium alloy core or a granular medium core that is removed after forming to obtain hollow shafts without the need of complex tools and highly loaded mandrels. It is shown that composite shafts featuring magnesium cores can be produced for a wide range of extrusion strains. Due to high hydrostic pressures in forward rod extrusion, the forming limit of magnesium at room temperature can be expanded. The observed bond strength between core and sheath is below the shear yield strength of utilized magnesium AZ31 alloy. Hollow shafts are successfully produced with the presented process route by utilizing zirconium oxide beads or quartz sand as a lost core. As the law of constant volume in metal forming is violated by compressible granular media, a simulation approach using a modified Drucker-Prager yield surface to model these materials is validated to provide a tool for efficient process design. Granular cores and magnesium alloy cores offer new possibilities in production of lightweight shafts by means of composite cold forging. Both process variants allow for higher weight savings than composite shafts based on aluminum cores.