植介入用精细金属丝材及其异质材料焊接技术研究进展

Research Progress of Implanting Fine Metal Wires and Its Heterogeneous Materials Welding Technology

随着生物医疗技术的不断进步以及微创手术的快速发展,植介入医疗器件对精细金属材料的需求量不断增加。医用导丝、心脏起搏器导线、功能性电刺激装置、牙矫正器、耳蜗植入装置等医疗器件,根据其植入尺寸及功能作用,都要求采用直径50~500 μm不等的精细丝材进行加工。传统医用金属丝材如316不锈钢、NiTi形状记忆合金、TC4等均含有Cr、Ni等毒性元素。这些医用金属丝材植入人体后,总会产生腐蚀与磨损,造成毒性元素的析出,极易引起炎症反应,对人体健康造成较大的危害。因此,近年来研究人员从选择合适的替代元素和优化制备工艺方面不断尝试改善医用金属丝材的性能,并取得了丰硕的成果,在保持高强低模的同时消除了毒性元素带来的危害。此后,出现了一批新型医用金属丝材,包括:Fe-17Cr-14Mn-2Mo-(0.45~0.7)N医用奥氏体不锈钢、Ti-22Nb-Fe合金、新型β钛合金等。尺寸的细小化对医疗装置中常用的异种材料的焊接技术提出了更高的要求。异种材料焊接的难点在于异种丝材化学成分的差异使得焊接过程易形成脆性化合物,从而恶化接头性能、降低焊接可靠性。近几年,研究人员对比固相连接、钎焊连接、熔化焊连接等多种焊接方法,发现微激光焊接方法具有能量密度高、焊缝窄、热影响区小、焊接变形小、高温停留时间短、熔化金属量少、光束方向性好、能进行精密加工等特点,在焊接异种金属丝材时效果最好。同时通过工艺参数的优化、过渡层的填充、工装夹具的设计以及接头失效形式分析、焊接连接机理的讨论,研究人员主要对316LVM(Low-carbon vaccum melting)不锈钢丝材及TiNi形状记忆合金丝材异种金属材料微激光焊接进行了系统研究,并取得了一些研究成果,实现了异种丝材焊接接头可靠性的大幅提升。本文系统梳理了医用金属丝材的发展及应用状况,针对异种精细金属丝材焊接的难点,从焊接方法、工艺研究及连接机理三个方面分别介绍了植介入用异种金属丝材焊接技术的研究进展,同时对该领域未来研究方向进行了总结与展望,以期为制备高可靠性的生物医用异质金属焊接接头提供帮助。

With the con ti nu ous adva nce of biomedical tech no logy and the rapid developme nt of mini mally in vasive surgery, impla ntati on of medical devices on the demand for fine metal materials is increasing. Medical wire, cardiac pacemaker wire, functional electrical stimulation device, dental appliance, cochlear implant device and other medical devices, according to its implant size and function, require the use of fine wire whose diameter ranging from 50 μm to 500 μm for processing. Traditional medical wire materials such as 316 stainless steel, NiTi shape memory alloy, TC4, etc. all contain toxic elements such as Cr and Ni. When these medical wire materials are implanted into the human body, more or less they will be corroded and worn, causing the precipitation of toxic elements, which will easily cause an inflammatory reaction and cause a great hazard. Therefore, in recent years, researchers have continuously tried to improve the performance of medical wire materials by selecting suitable substitute elements and optimizing the preparation process. And they have achieved fruitful results, while maintaining high strength and low mold while elim in at ing the harm caused by toxic eleme nts. A nu mber of new medical wire materials have appeared: Fe-17Cr-14Mn-2Mo-(0.45-0.7) N medical austenitic stainless steel, Ti-22Nb-Fe alloy, new beta titanium alloy and so on. Smaller size not only requires the performa nce of the material itself, but also a highly reliable weld ing tech no logy, especially for the weldi ng technology of dissimilar materials which commonly used in medical devices. The difficulty lies in the fact that the chemical composition of the different kinds of wires makes the welding process easy to form brittle compounds, thereby deteriorating the joint performance and reducing the welding reliability .In rece nt years, researchers have compared various weld ing methods such as solid-phase conn ectio n, brazed joint, and fusi onwelded joint. It is found that the micro-laser welding method has high energy density, narrow weld seam, small heat-affected zone, small welding deformation, and high temperature retention. Short time, less amount of molten metal, good beam direction, and precision machining are the best results when welding dissimilar metal wires. At the same time, through the optimization of process parameters, the filling of the transition layer, the design of the fixture, the analysis of the joint failure form, and the discussion of the welding connection mechanism, the researchers mainly focused on 316LVM ( low-carbon vaccum melting) stainless steel wire and TiNi shape memory alloy wire. Micro-laser welding of dissimilar metal materials have been systematically studied, and some research results have been obtained, which can greatly improve the reliability of dissimilar wire solder joints. This paper systematically combs the development and application of medical metal wire materials. Aiming at the difficulties in welding dissimilar fine metal wire materials, the research progress of welding technology of dissimilar metal wire materials is introduced from three aspects : welding method, process research and connection mechanism. The future research direction of this field is summarized and forecasted, which can help to prepare high reliability biomedical heterogeneous metal welded joint.