不銹鋼薄板精微彎曲成形之研究

Abstract

隨著製造領域中微型化趨勢的不斷發展，微型電子之零組件需求量越來越大，其具有低成本、高生產效率、成形件強度高等優點。本研究將針對廣泛應用於電子通訊零組件之不同厚度不銹鋼(Stainless steel)301材料，進行薄板微彎曲成形之研究。 由於材料尺寸微小化後，其材料性質會隨尺寸效應(Size effect)而有所改變，因此傳統巨觀尺寸彎曲變形的研究模式不一定適用於精微彎曲(Micro-bending)之分析，因此，本研究蒐集了傳統沖壓彎曲成形之技術資料，並整合目前已發表之精微成形相關技術資料，歸納出精微沖壓彎曲成形之關鍵技術；本文先規劃針對不銹鋼材料微小化後之尺寸效應進行拉伸實驗及彎曲實驗分析，以取得精微尺寸之材料性質及彎曲回彈特性。至於材料之塑性變形則以CAE分析技術來觀察材料於厚度方向的應力分佈，並藉此來預估回彈後的角度，並與實驗作一比對驗證。本文亦針對各材料與製程參數，包括：材料尺寸、晶粒尺寸大小(Grain size)、彎曲R角、摩擦係數與成形方式，對回彈現象之影響進行探討。並透過微硬度實驗之觀察，以了解薄板於微彎曲後之硬度分布情形。藉由上述的研究，將可提升精微薄板彎曲成形技術，將沖壓元件薄型化，以掌握精微沖壓成形的關鍵技術。

With the ongoing miniaturization in manufacture, there is a growing demand on micro products that have many advantages, such as lower cost, efficient mass production, higher strength, etc. Among the micro-productions, the micro-bending of thin stainless steel sheets has obtained a variety of applications in the IT industry. Though the macro-bending process has been well-developed, the design concepts may not be directly applied to the micro-bending due to the size effect occurred in the micro-forming processes. In the present study, the micro-bending of 301 stainless steel sheets with different thicknesses was studied. A thorough literature survey regarding the macro-bending technology and the current development status of micro-bending was made first. In order to obtain the material properties of the miniaturized 301 sheets, the tensile tests were conducted. The bending tests were also performed to examine the effects of sheet size and grain size on the micro-bending processes. The size effects occurred in both the tensile tests and the bending tests were observed. The effects of the process parameters, such as tooling corner radii and friction condition, on the micro-bending of thin 301 sheets were studied as well in the present study by both the experimental approaches and the finite element analyses. The stress distributions calculated from the finite element simulations explained the deformation mechanics of the springback occurred in the micro-bending of thin steel sheets. And it is found that both the sheet size and the grain size, in addition to the process parameters, have significant effects on the springback phenomenon occurred in the micro-bending of 301 stainless steel sheets. The results obtained in the present study could be valuable references to the future researches on the micro-bending of other kinds of thin metal sheets.