高強度球墨鑄鐵表面火焰硬化熱處理之探究

Study on Surface Flame Hardening of High-Strength Ductile Cast Irons

李俊緯(June-Wei Lee)

指導教授 ： 潘永寧

國立臺灣大學/工學院/機械工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.11313

摘要

本研究針對高強度球墨鑄鐵之鑄件進行表面火焰硬化處理，其目的為達到所需之表面硬度以提升耐磨耗性。在實驗方法上，首先建立最佳之單道火焰-單一行程之表面硬化操作條件，條件包括火焰移動速度與火焰噴嘴與試片之間距，以達到試片表面全面性之硬化效果。研究結果顯示，火焰移動速度為70mm/min，並且以20mm為火焰噴嘴與試片表面之間隙為最佳之操作條件，可以產生約8-9mm之穩態橫向硬化寬度(HRC >50)與約57HRC之平均表面硬度。
再者，測試單道火焰-複數行程處理，採用穩態之橫向硬化寬度作為後續火焰承接之距離。結果顯示，先行硬化之區域會因下道承接火焰所傳遞之熱能而發生回火軟化問題，表面硬度大約從55~56HRC之完全硬化值減少至大約45HRC。此外，該軟化區域可從硬化區域的邊緣延伸到兩側周圍約10.45~10.55mm。結果明顯的表示，使用單道火焰-複數行程處理，無法達成試片表面全面硬度為50HRC以上之水準。
最後，表面採用多道火焰-同步單次行程處理。結果顯示，多道同步火焰以9mm之間距可達到全面性硬化之效果，其硬化深度約為2.00~2.20mm。

關鍵字

高強度球墨鑄鐵 ； 火焰表面硬化 ； 淬火 ； 回火

並列摘要

In this study, flame (surface) hardening was performed on the high-strength grade ductile cast irons to achieve the required surface hardness for wear resistance purpose. Firstly, a single flame – single pass was conducted to establish the optimal operation conditions, including the flame travel speed and the gap between the flame nozzle and the surface of the workpiece, to achieve a full surface hardening effect. The experimental results indicate that a flame travel speed of 70mm/min, and a gap of 20mm between the flame nozzle and the surface of the workpiece were determined to be the optimal operation conditions that can produce a transverse hardened width of around 8-9mm with an average surface hardness of some 57 HRC. Secondary, tests with single flame – multiple pass were performed to examine once again the hardened width and also the possible softening effect due to tempering caused by the thermal energy from the subsequent neighboring flame pass. It was found that the already hardened regions were softened by the subsequent neighboring flame pass. As a result, the surface hardness was reduced to around 45HRC from a fully hardened value of some 55~60HRC. In addition, the softened region can extend up to around 10.45-10.55 mm both sides from the edge of the hardened region. It is quite obvious that using single flame – multiple pass is not practically feasible if the minimal surface hardness of 50HRC is going to be obtained. Alternately, surface hardening using multiple flame – single pass was proposed and test runs were conducted. The results show that full hardening was achieved across the hardened region with the hardened width (single flame) and depth being 8~9mm and 2.0~2.2mm, respectively.

並列關鍵字

High-strength ductile cast iron ； Flame hardening ； Quenching ； Tempering

參考文獻

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