鍛造零件之鍛造變形率對鍛後滲碳熱處理之影響

The Effect of Forging Deformation Percentage on the Carburizing Treatment of Forged Parts

李宗威(Tzung-Wei Lee)

指導教授 ： 林維新

共同指導教授 ： 曾春風(Chun-Feng Tseng)

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(2011年)

https://doi.org/10.6827/NFU.2011.00028

摘要

鍛造加工是藉著衝擊或擠壓的方式，將材料在不同的模具和工具內，以塑性變形方式改變其形狀但不改變其質量及材料成分的情況下，得到所要求形狀、尺寸及機械性質的零件。鍛造加工可控制金屬的流動及晶粒的結構，而使得鍛造的零件具有良好的機械強度及韌性，需要承受高負載及高使用頻率的機械零件，經常採用鍛件方式製造。低碳鋼料進行鍛造加工以後，必須實施滲碳及淬火處理，以提高其表面硬度。
本研究針對低碳鋼以三種不同鍛造方式(冷鍛、溫鍛、熱鍛)進行不同鍛造變形率之鍛造，然後實施不同碳勢之滲碳及淬火處理，經截面顯微組織觀察及硬度測試，以了解不同鍛造方式、鍛造變形率、碳勢對滲碳熱處理的影響。並利用有限元素軟體分析鍛造變形率對滲碳層碳濃度分佈、滲碳深度、表面硬度之影響。並比較實驗結果與有限元素軟體分析的差異。
實驗結果顯示，鍛造變形率會影響滲碳層及非滲碳層內部顯微組織；在相同鍛造變形率下，熱鍛後滲碳之晶粒最粗，溫鍛者其次，冷鍛後滲碳晶粒最細。無論何種鍛造方式或碳勢，滲碳深度隨鍛造變形率增加而下降，表面硬度隨鍛造變形率增加而增加。碳勢CP＝0.4%與0.8%時，橫向、縱向滲碳深度隨鍛造變形率增加而減少，硬度值隨鍛造變形率增加而稍微增加，碳勢CP＝1.2%時，橫向、縱向滲碳深度較不受鍛造變形率的影響，硬度值亦不受鍛造變形率影響；爐氣碳勢CP＝0.8%時其橫向或縱向滲碳深度很相近，且因較不會產生過滲碳可避免淬裂，是滲碳熱處理時較佳的爐氣碳勢。

關鍵字

鍛造變形率 ； 滲碳處理 ； 顯微組織 ； 碳勢 ； 表面硬度

並列摘要

The process of forging is completed by impacting or extruding when the materials are put in different dies and tools undergoes the plastic deformation. This process will convert the shape without changing the actual composition and mass of the materials in order to obtain the required shape, size, and mechanical property of parts. Forging can control the metallic flow and structure of the grains in order to make forged parts with better mechanical strength and toughness which is needed to withstand highly overload resistant and frequent used mechanical parts. Single piece forging process is commonly adapted.
The low-carbon materials of steel after forging must go through carburizing and quenching in order to improve the hardness of steel surface. The study focuses on the of forging deformation percentage in accordance with different steel materials that undergoes different carburizing and quenching condition. More so, the microstructures observation on carburized cross-section and micro-hardness test can help understanding how forging type, forging deformation percentage, and carbon potential affect carburizing process. The study helps to look for the better resolve when carburizing different percentage of forging deformation from various steel materials, in which, might provide technical reference on the company of forging technology and heat treatment.
According to the results, forging deformation percentage affects the internal microstructure of carburized and non-carburized layer. Under the same forging process, the grain size after the carburizing – the greater, the hot forging is, secondly the warm forging is, the finer, the cold forging is. The carburizing depth and the surface hardness both increase as the forging deformation percentage increases. When carbon potential is at 0.4% or 0.8%, the transverse and longitudinal depth of carburization both decrease as the forging deformation rate increase. The hardness slightly increases as the forging deformation rate increase. When carbon potential is at 1.2%, the forging deformation rate has no effect on transverse and longitudinal depth of carburization, and hardness. When carbon potential is at 0.8%, transverse and longitudinal depths of the carburization are both similar. It is most likely to produce less excessive carburized to avoid quenching crack when harden.

並列關鍵字

forging deformation percent ； carburizing treatment ； microstructure ； carbon potential ； surface hardness

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