Cold Drawing of Magnesium Alloy Tubes for Medical

Abstract

Magnesium alloy is the lightest in practical metals, and it is used for small home appliance products and automobile parts. It is also expected to be a new material for medical stents, because of its possibility of systemic absorption. But, it is known that the processing of magnesium alloy is very difficult and many magnesium alloys are hot-worked. Therefore, surface quality and strength of products and processing cost are the points when cold-plastic working of magnesium alloy is carried out. The purpose of this study is fabrication of a tube of magnesium alloy to improve stent strength and to reduce processing cost. Fineness, thinness, adequate strength and high-quality surface are required for stents of the medical tube. Therefore, firstly, plug drawing was carried out, because it was thought to be one of the methods for satisfying the requirements. But, it proved to be impossible to apply this method, because magnesium alloy is too brittle for plug drawing. Secondly, soft-metal mandrel drawing was tried. Drawing was possible, but it was difficult to extract the mandrel, because there is a possibility that the tube might break due to its high drawing stress. So, fluid-mandrel, a new method for mandrel drawing, was carried out. As a result, the fabrication of a fine and thin-walled tube for a stent became possible. And it was found that the wall-thickness of the tube was as thin as existing medical tubes. In fluid-mandrel drawing, fluid is used as mandrel. So, it is easy to extract mandrel after drawing. And it is possible to prevent tube break during drawing, because drawing stress is lower than that of soft-metal mandrel drawing.