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(J. W. Lee) ； 潘永寧(Y. N. Pan)

《鑄造工程學刊》 41卷2期 (2015/06) Pp. 1-8

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，以達到所需要之表面硬度以提升耐磨耗性。在實驗方法上，首先針對單道火焰-單次行程之表面硬化處理，建立最佳之操作條件，包括火焰移動速度以及火焰噴嘴與試片之間距，以獲得試片表面之全面性硬化效果。分析結果顯示，70mm／min火焰移動速度+20mm火焰噴嘴與試片表面間隙係為最佳之操作參數，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。接者，進行單道火焰-複數行程之表面火焰硬化處理，以測試橫向硬化寬度以及可能之回火軟化現象。實驗結果顯示，先前被火焰硬化之區域會因承接下一道火焰所傳遞之熱能而發生回火軟化現象，表面硬度從約55～56HRC之完全硬化值降低至約45HRC。實驗結果明確顯示，使用單道火焰-複數行程之表面硬化處理，無法達到全面表面硬度高於50HRC之結果。最後，本研究採用多道火焰-同步單次行程之表面硬化處理方法，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（HRC＞50），其硬化深度約為2.10mm。

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, for achieving a full surface hardening effect. The experimental results indicate that a flame travel speed of 70 mm/min, and a gap of 20 mm 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 8-9 mm 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 the tempering effect 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 45 HRC from a fully hardened value of some 55~60 HRC. It is quite obvious that using single flame-multiple pass is not practically feasible if the minimal surface hardness of 50 HRC is going to be obtained. Finally, surface hardening treatments using multiple flame-single pass were conducted. The results show that full hardening was achieved across the hardened region with the hardened width (single flame) and hardened depth being 8~9 mm and 2.1 mm, respectively.

並列關鍵字

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