傘齒輪差溫擺輾熱鍛之研究

An Analysis of Thermal Differential Orbital Hot Forging for Bevel Gear

吳維倫(Wei-Lun Wu)

指導教授 ： 許源泉

國立虎尾科技大學/工程學院/創意工程與精密科技研究所/碩士(2010年)

摘要

擺輾鍛造是一種局部接觸的新製程、以漸進式的方式使得材料逐漸成形。它具有省力、精度高、噪音小等優點，因此受到了各國學者及工業界專家的普遍重視並得到日益廣泛的應用。但是，由於作動方式複雜， 材料流動難以掌握， 所以在其理論研究方面還並不成熟，因此在製作設計增加了許多難度，使得產品製作周期較長、生產不易等問題發生，也因而限制擺輾鍛造的應用與發展。
利用金屬加熱時會發軟化現象，且在一定的溫度範圍內，溫度越高，軟化程度也愈高，金屬流動也就越容易。利用這種物理現象，一種新的無模鍛造誕生出來，即差溫無模鍛造，這種設想讓某些區域的金屬流動變得更容易。如果溫度的分佈能夠被合適的控制，那麼利用簡單的鍛壓方法，就可使複雜的零件初步成形，進而實現零件近淨成形。
為了有效瞭解差溫對擺輾鍛造的成形方式，本文應用三維剛塑性有限元素法，進行差溫擺輾鍛造數值模擬，即在模擬過程中對上模擺角及轉速與下模進給率等進行模擬，並以差溫加熱方式在胚料較難以變形之區域施加高溫溫度促使胚料有效的變形。
經由研究結果發現在胚料下部區差溫加熱可以有效的改善擺輾鍛造的變形能力，溫度之梯度亦較明顯。在等效應變上由於擺輾製程中不均勻的變形導致各部位之等效應變較不一致， 但可以發現最大應變值發生在胚料底部與頂部模具接觸之區域；而製程參數上以擺角及轉動速度越大時負荷越小，進給速度則越慢負荷越小，溫度則是越高溫時成形效果較佳，摩擦因子則對於擺輾鍛造影響較小。在微觀組織上則是以溫度與變形量為主導，當溫度越高時晶粒細化越明顯；而由於擺輾鍛造中胚料與模具是局部接觸變形，熱能在傳遞上相對分佈較不均勻，因而動態再結晶在不同之區域分佈也較沒有一致性；在相轉換時溫度越高所需之變化時間越久，而以不同介質焠火得到之組織強度亦不同。

關鍵字

數值模擬 ； 擺輾成形 ； 差溫加熱 ； 動態再結晶

並列摘要

Orbital forging is a new process featuring a local contact, which forces the metal material to gradually deform by incremental approach. This process has the advantages of labor-saving, high precision, and low noise, etc., and so is highly valued by many scholars and industry experts and is widely applied too. However, due to the complicated action modes and hard-controlled material flow, its theoretical research has not been mature until now. Because difficulties increase in production design, problems with extended production cycles and product manufacturing appear, and therefore the applications and development of orbital forging are restricted.
In general, metal is softened after heating, and at a certain temperature range, the higher temperature enhanced the higher softening effect, and metal flow become easier. Based on this physical phenomenon, a new dieless forging, thermal-differential forging, has been developed, which makes the metal flow in certain regions become easier. If the temperature distribution could be suitably controlled, the complex parts could be initially formed by using simple forging method, thus the near net shape forming will be achieved.
To effectively understand the influence of local heating on forming of orbital forging, the three-dimensional rigid-plastic finite element method was applied in the current study to the numerical simulation of differential thermal orbital forging. Namely, to effectively promote the deformation of the billet, the poorly deformed region was locally heated at a high temperature. In addition, the influence of the upper die orbital angle, rotation speed, and lower die feed rate on the thermal differential hot forging for bevel gear were also explored.
Results showed that local heating in the lower zone of billet could not only effectively improved the deformation ability of orbital forging, but also generated obvious temperature gradient. Due to the uneven deformation in orbital forging processes, the equivalent strain distributed over the bevel gear was less consistent, but the maximum strain value could be found at the bottom and top of the die/billet contact regions. As for the influence of process parameters, the forming load was greater when the orbital angle was greater and rotation speed higher, but the forming load was lower when the feed rate was slower. The forming effect was better at higher temperature, but the orbital forging was less affected by the friction factor.
Temperature and deformation are the major factors in affecting the microstructure of metal, and the grain refinement is more obvious as the temperature gets higher. Because the interface of billet and die in orbital forging is a local contact deformation, the distribution of heat energy transfer is more uneven. Therefore, the distribution of dynamic recrystallization in different regions is not uniform. It requires longer time in phase transformation when it is at higher temperature, and the structural strengths were different when using diverse quenching media.

並列關鍵字

Numerical simulation ； Orbital forming ； Thermal differential forging ； dynamic Recrystallization

參考文獻

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