鉻鉬鋼以流體床進行氮化熱處理之研究

A Study of Nitriding SCM440 Steel in Fluidized Bed

張聰亮(Chang Tsung-Liang)

《鑛冶：中國鑛冶工程學會會刊》 39卷1期 (1995/03) Pp. 122-130

摘要

本研究係以中鋼公司生產之SCM 440（有氮化效果鋼料）棒鋼以流體床氣體爐法進行表面氮化熱處理，觀察其氣化特性，並與標準氮化鋼SACM 645及高速鋼YXR 3相比較。試片以560℃及不同時間進行氮化處理。由各種機械性質測試顯示SCM 440可藉氮化熱處理增加其硬度，但硬度不如SACM 645及高速鋼高。氮化時間增長可增加氮化深度，但白層亦隨之增加，衝擊值亦下降。SCM 440以流體床進行氮化，由X-光繞射及金相圖形顯示，氮化時間超過20小時以上，SCM 440表會面形成比白層更硬脆的Fe_(2.5)N灰色層，不利於機械性質，所幸以流體床進行表面氮化熱處理只需15－18小時即可達到一般氣體爐需70小時的氮化效果，減少了以往氮化後必須再研磨的程序。

並列摘要

In this study, SCM440 steel which was produced by China Steel Corp. was nitrided in a fluidized bed. Then the property of the nitrided layer was investigated and compared with that of SACM645 and YXR3 high speed steels. Specimens were nitrided at 560℃ for various times. Tests on mechanical properties show that SCM440 could be hardened by nitriding, but the hardness is lower than that of SACM645 and YXR3. The longer heat treating time the deeper hardened layer, and the white layer is also increased. X-ray and metallographic examinations show that a Fe_(2.5)N phase is formed on the surface of SCM440 when nitriding time is more than 20 hours. Fe_(2.5)N phase is very brittle and it will decrease the mechanical property. Fortunately, the effect of 70 hours nitriding in an ordinary gas furnace is equal to 15-18 hours in a fluidized bed, so if steel is nitrided in a fluidized bed, the grinding process may be omitted.