智慧控制負荷電氣端鍛之模擬與實驗研究

Simulation and Experiment of Electrical Upsetting Process with Intelligent Control Load

洪偉哲(Wei-Jhe Hong)

指導教授 ： 許源泉

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2012年)

https://doi.org/10.6827/NFU.2012.00081

摘要

電氣端鍛具有投資設備低、鍛件桿部尺寸精度高等優點，利用胚料在電氣端鍛成形的餘溫將有助於二次鍛成形，應用鍛造成形使得產品具有良好的纖維流線，有益於強度的提升；因此，電氣端鍛普遍用於高徑比大的產品上，如製造汽機車汽門、各式軸類零件與大型風電用螺栓等。本研究在探討電氣端鍛智慧控制頂桿負荷對其製程的影響，智慧控制負荷分為定負荷與變負荷兩種，定負荷為目前市面上常見的電氣端鍛機使用方式，成形形狀則須依靠電極頭與頂桿速度兩者進行搭配，而使用變負荷方式則使得成形後的形狀較多變，使得鍛縮長度較具靈活性，有利於產品更加多元化。

本研究是利用有限元素軟體DEFORM-2D進行AISI 1045中碳鋼之定負荷與變負荷電氣端鍛製程分析，以了解在電氣端鍛時胚料受到不同負荷之變形、應力、應變、溫度、晶粒尺寸等分佈，並且探討其頂桿負荷、胚料直徑、初始距離等相關參數，對定負荷與變負荷電氣端鍛之鍛縮長度與成形溫度之影響。 模擬結束後，再藉由電氣端鍛定負荷實驗來驗證有限元素模擬之準確性，檢測其鍛縮長度、加熱時間與成形形狀等。為了解不同定負荷中電氣端鍛的晶粒大小與硬度分佈等，所以利用工具顯微鏡與維氏硬度試驗機進行微觀組織與硬度分析。

研究結果顯示，在定負荷模擬中，利用DEFORM-2D後處理模組可順利將電氣端鍛成形之結果完整呈現，如應力、應變、溫度場與晶粒尺寸等，有助於對成形後的胚料更進一步的探討。由於電氣端鍛屬於差溫成形，所以溫度集中於電極頭與夾持電極的胚料內。胚料整體受到頂桿推擠所以都有產生應力，而最大應力發生於夾持電極夾持處，但由於該處的溫度較低，所以變形仍發生在胚料受熱處；胚料產生應變集中於端部，桿件直部並不變形所以不產生應變，符合電氣端鍛優點－桿件直部精度高。不論在幾何外型、鍛縮長度或成形時間上，有限元素模擬與實驗結果相當符合，更加驗證DEFORM-2D應用於電氣端鍛成形之可靠性與可行性；利用有限元素模擬將有助於節省實驗時間與試模之成本，而每次所存取的資料可成為往後設計的參考，對於新的產品設計上將有事半功倍的效果。在硬度與平均晶粒尺寸中，所輸入的定負荷越小，則因為溫度高的關係，所得的硬度也高；而各定負荷胚料之鼓脹區域，由於受到鍛壓的關係，所以平均晶粒尺寸明顯可看出比原始素材細小，並且在應變最大處晶粒細化的效果就越明顯。

在變負荷模擬中六種曲線之胚料外形，由於負荷週期增加，所以開始產生波浪形狀；而正弦波在一倍週期中並不產生波浪形狀，但在二倍週期後即開始產生波浪形狀，並且隨著負荷週期越多，產生的波浪形狀也越多，波浪數量為偶數；而在餘弦波、V形波、倒V形波、直線-1、直線-2五種變負荷曲線中，一倍週期中即會產生波浪形狀，波浪數量為奇數；而六種變負荷曲線隨著週期倍數越多波浪數量越多，但波浪形狀就越不明顯。
電氣端鍛定負荷與變負荷製程參數的研究中，不論是在定負荷或變負荷，在相同加熱條件下，其影響鍛縮長度與成形溫度的重要參數為頂桿負荷與胚料直徑；隨著頂桿負荷越大直徑越小，因鍛縮長度越大，而成形溫度將會越低 ；在初始距離中雖然影響胚料所加熱的長度，但對鍛縮長度與成形溫度的影響較小。

關鍵字

有限元素分析 ； 電氣端鍛 ； 智慧控制 ； 汽門 ； 軸類零件

並列摘要

The advantages of electrical upsetting with low investment in equipment and high precision for forging rod size, it will help the second forging of the billet’s warmth after electrical upsetting. The product has good fiber flow lines by using forging, and it can upgrade the intensity. So, the electrical upsetting is widely used in height to diameter ratio of products, such as the manufacture of steam locomotive valve and all kinds of shaft parts and large-scale wind power with bolts. This study investigates the impact of electrical upsetting process by intelligent control push rod. The intelligent control is divided into constant load and variable load. The constant load is used in common electrical upsetting machine, and the forming shape has to rely on both speed of electrode head and push rod. The forming shape can be changed by using variable load, and the products of forging length can be more flexible and more diversified.

In this study, the finite element simulation software DEFORM-2D was used to analyze the electrical upsetting process for AISI 1045 carbon steel with constant and variable load. To understand the billet at the end of forging deformation, stress, strain, temperature and grain size distribution of different load. And to explore the parameters of push rod load, the diameter for the billet, the initial distance and the impact of forging length and forming temperature. After the end of the simulation, the finite element simulation was verified the accuracy by electrical upsetting experiment of constant load, and testing its forging length, heating time and forming the shape. To analyze microstructure and hardness by using tool microscope and the Vickers hardness machine in order to understand the distribution of grain size and hardness, after electrical upsetting with constant load.

The results showed that the electrical upsetting forming products could be completely present by using DEFORM-2D’s postprocessor, such as stress, strain, temperature and grain size. It will help to further explore billet after forming. The electrical upsetting belongs to differential temperature forming, so the temperature is concentrated in the electrode head and the clamping electrodes of billet. The whole billet has the stress by the push rod pushed, and the maximum stress occurs in the electrode clamping of the holder. Because there is a lower temperature, the deformation is still occurred in the heat zone of the billet. The strain concentrates on the end of the billet. Because the rod straight wasn’t deformed, it didn’t generate strain. It conforms in electrical upsetting advantages. No matter in geometry, forging length or forming time, the result between finite element simulation and electrical upsetting experiment are quite consistent. It was verified the reliability and feasibility in the DEFORM-2D applied to the electrical upsetting. The cost can be saved of experiment time and mold trial by using finite element simulation. Every time we access information can became the next reference design, there will be half the work with double results for new product design. In the hardness and average grain size, entering smaller constant load, the hardness will be higher because the temperature will be higher. Because the bulging region of billet is forging with constant load, the average grain size is smaller than original material. And the grain refinement effect obvious at maximum strain.

The forming shape of the variable load after electrical upsetting on six different times-load curve. Because of the load cycle are increasing, it start generating the wave shape. The sin wave is not generating the wave shape in first cycle, but it start generating the wave shapes in second cycle. And the load cycle becomes more, the wave shapes becomes more. The wave number is odd. In the Cos wave, V wave, inverse V wave, straight line-1, straight line-2, five different times-load curve, they were generated wave shape in first cycle, and the wave number is even. The six different times - load curve have more wave numbers in more cycle, but the wave shape isn’t obvious.

In the study of electrical upsetting process with constant load and variable load, no matter in constant load or variable load in the same heating conditions, the most important impact of forging length and forming time are push rod load and the diameter of the billet. Along with that the bigger the push rod goes and the smaller its diameter becomes, the forming temperature will be lower due to the forging length becomes longer. Although the impact of the billet heating of the initial distance, but a smaller impact on the length of the forging and the forming temperature.

並列關鍵字

Finite Element Method ； Electrical Upsetting ； Intelligent Control

參考文獻

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