Fabrication Process for Ni-Ti Shape-Memory-Alloy Fine Tubes Used in Medical Tests

形状记忆合金细管在导管和注射针头中的应用有望用于医学测试和治疗，因为它们不与生物体发生反应，并且在医疗和测试时可以增加其扭矩传递特性，便于临床应用，同时减少患者的不适。本研究以Ni-Ti形状记忆合金为研究对象，研究了细管拉丝和拔丝的最佳拉丝条件，Ni-Ti合金是一种具有超弹性和形状记忆合金特性的优良功能材料；然而，与实用合金相比，它们在易成形性方面较差。因此，我们对易拉伸润滑剂的选择、拉伸条件的优化（包括模具角度和面积缩小）、拉伸极限的明确、拉伸后和热处理后形状恢复率的测定、拉伸细管内外表面粗糙度的测定等进行了研究。从理论上讨论了用有限元法拉深时的应力应变分布。根据所获得的结果，我们明确了在细管截面积减少约20%的情况下，歌唱和堵塞拉伸是可能的；所获得的基础数据可以在实际生产中得到有效利用。

The utilization of shape-memory alloy fine tubes in catheters and injection needles for medical tests and treatments is expected, since they do not react with organisms, and their torque transfer feature can be increased at the time of medical treatment and tests, facilitating easy clinical application, while reducing the patient's discomfort.In this study, using Ni-Ti shape memory alloys, we investigated the optimal drawing conditions for the sing and plug drawing of fine tubes, Ni-Ti alloys are excellent functional materials with ultra-elasticity and the characteristics of shape memory alloys; however, they are inferior with respect to ease of formability compared with practical alloys. Therefore, we conducted studies on the selection of an easy-to-draw lubricant, the optimization of drawing conditions including die angle and reduction of area, the clarification of drawing limits, the determination of shape-recovery percentages after drawing as well as after thermal treatment, and the determination of the inner- and outer-surface roughness of drawn fine tubes. We also discussed theoretically the distributions of stress and strain during drawing using a finite element method. Based on the results obtained, we clarified that sing and plug drawing with a reduction in the cross-sectional area of the fine tube of approximately 20% was possible; the basic data obtained could be effectively utilized in actual production.