Li Kaisong, Wang Zhangke, Liu Xuefeng
Department of materials processing engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Beijing Laboratory of Metallic Materials and Processing for Modern Transportation, University of Science and Technology Beijing, Beijing 100083, China.
Materials (Basel). 2019 Apr 23;12(8):1320. doi: 10.3390/ma12081320.
A semi-dieless drawing technology has the advantages of producing a large deformation in a single pass and achieving high-precision dimensions of the finished products. However, instabilities can easily occur in a technique with a large amount of deformation, resulting in its failure. Herein, the deformation behavior of a wire during semi-dieless drawing is studied by finite element simulations. The instability mechanism of the semi-dieless drawing is proposed and validated by experiments. The experiments are conducted under the following conditions: a heating temperature of 950 °C; a distance between the die and heating coil of 20 mm; a feeding speed of 0.25 mm/s; a drawing speed range of 0.38-0.53 mm/s, and a die diameter range of 1.8-2.4 mm. The results show that by increasing the drawing speed or decreasing die diameter, the diameter fluctuation of the dieless drawn wire increases, and the semi-dieless drawing process easily becomes unstable. The diameter of the entering wire shows a fluctuating increasing trend owing to the variation in the drawing speed, which results in the instability during the semi-dieless drawing. The validity of the finite element model is verified by comparing the numerically predicted value and experimentally measured value of the drawn wire diameter.
一种半无模拉拔工艺具有单次拉拔变形量大且能实现成品高精度尺寸的优点。然而，在变形量较大的工艺中容易出现不稳定性，导致其失效。在此，通过有限元模拟研究了线材在半无模拉拔过程中的变形行为。提出了半无模拉拔的失稳机制，并通过实验进行了验证。实验在以下条件下进行：加热温度为950℃；模具与加热线圈之间的距离为20mm；进给速度为0.25mm/s；拉拔速度范围为0.38 - 0.53mm/s，模具直径范围为1.8 - 2.4mm。结果表明，通过提高拉拔速度或减小模具直径，无模拉拔线材的直径波动增大，半无模拉拔过程容易变得不稳定。由于拉拔速度的变化，进线线材的直径呈现出波动增大的趋势，这导致了半无模拉拔过程中的不稳定性。通过比较拉拔线材直径的数值预测值和实验测量值，验证了有限元模型的有效性。
