高溫淬火前持溫時間對ADI微觀組織及表面硬度之影響

Effects of Holding Time on Microstructure and Case Hardness of ADI before Quenching

許正勳(C. H. Hsu) ； 洪鈞泰(C. T. Hung) ； 劉洪才(H. T. Liu)

《鑄造工程學刊》 40卷4期 (2014/12) Pp. 25-30

摘要

本研究主要是將沃斯回火延性鑄鐵（ADI）試片先置入900℃高溫爐分別持溫1、2、4及6min，再進行淬火（Water quenching）處理，然後探討淬火前不同的持溫時間對試片微觀組織、表面硬度及耐磨耗性之影響。實驗結果顯示：由於高溫淬火效應，ADI表層組織會變態成麻田散鐵相，使得ADI表面硬度明顯地提高（450→950HV_(0.1)），而且隨著持溫時間的增加，硬化層深度亦增加；然而必須注意的是，當持溫時間為2-min時，ADI內部組織與麻田散鐵相之混合區域會產生微裂縫，甚至於當持溫時間超過4-min以上時，則微裂縫會貫穿至表面；反之，若持溫時間控制得宜（～1min），則ADI內部組織不但不會產生微裂縫，而且因表面硬度的提高使耐磨耗性獲得改善。

關鍵字

沃斯回火延性鑄鐵 ； 淬火 ； 微觀組織 ； 硬度 ； 耐磨耗性

並列摘要

In this study, the ADI specimens were first heated at 900 °C for 1, 2, 4, and 6 minutes, respectively, and then quenched in water. The purpose is to explore the effect of holding time on microstructure, surface hardness, and wear resistance of ADI. The results show that there is a martensitic formation on the surface of ADI due to the quenching effect, resulting in an evident increase of hardness on the ADI's surface (450→950 HV_(0.1)). Moreover, the depth of case hardening increased with increasing holding time. However, it must be noticed that when holding time is 2 minutes, some micro-cracks take place on the internal structure of ADI with a mixture of ausferrite and martensite. When the holding time is over 4 minutes, the cracking could penetrate the surface. In contrast, the holding time controlled (~1 min) properly could not only avoid the generation of cracks, but also increase surface hardness of ADI to improve the wear resistance.

並列關鍵字

Austempered ductile iron ； Quenching ； Microstructure ； Hardness ； Wear resistance