- 期刊
氮含量及熱處理對於高碳軸承鋼SUJ2形成共析碳化物影響之研究
The Study of Eutectoid Carbide in SUJ-2 Wear Resistant Steel by Various Nitrogen Contents and Heat Treatment
摘要
鋼珠市場上的佔有率最高之鋼種為SUJ2，其碳含量高達1.0Wt％，為過共析鋼。由Fe-Fe3C平衡相圖觀察，易產生共晶碳化物及共析碳化物等組織，造成加工之困難。本研究以合金添加法及不同時效熱處理條件，探討氮含量及熱處理對於鋼鐵材料機械性質的影響。實驗中使用高週波熔煉爐在氮氣氛下進行熔煉，熔煉時在高碳鋼中添加氮鉻鐵合金提高其氮含量，並進行硬度試驗（Hardness Test）及耐磨耗試驗（Wearing Test）等機械性質測試，實驗結果顯示，氮含量越高，則磨耗的重量損失越小，磨秏軌道與磨屑經EDS分析顯示有大量氧元素與微量鎢元素殘留。熱處理方面，首先將試片加熱到1250℃進行一小時之固溶化處理，待試片冷卻至室溫後，接著分別進行700℃與800℃、15小時與30小時之球化熱處理，觀察其熱處理後之碳化物析出情形，經由EDS分析後可證明其碳當量均比基地相高出許多，由SUJ2的XRD分析可發現熱處理前SUJ2-bar與SUJ2-h.r.試片（氮含量為50ppm）均為肥粒鐵相，N378、N238與N172（氮含量分別為378ppm、238ppm、與172ppm）為麻田散鐵相，但球化熱處理後均為肥粒鐵相。
並列摘要
SUJ2 steel which has carbon content over 1 wt% is the most used in ball bearing industry. Fe-Fe3C phase behavior diagram indicates that the eutectic and eutectoid carbides can easily precipitate in the steel make the ball bearing manufacturing difficult. In this research the mechanical properties of this steel doped with various alloying elements and heat treated under different conditions are studied. The high-carbon steels are alloyed with Fe-Cr-N alloy and melt in high frequency furnace under nitrogen atmosphere. Hardness and wearing tests are performed. The test results show that the weight loss after wearing test decreases with increasing nitrogen content and that the abraded and spent materials have a large amount of oxides as detected by EDS analysis. After cooling to room temperature, steel samples were solubilized at 1250℃ for 1 hour, and then thermally spheroidized at 700℃ and 800℃ for 15 hours and 30 hours, respectively. Precipitation of carbide was observed after the heat treatment, and the carbon equivalent of carbide is much higher than that in the base metal. The results of XRD tests show that the main structure is ferrite in both non-treated SUJ2 and treated SUJ2 (N:50 ppm) and martensite in N378 (N:378 ppm), N238 (N:238 ppm) and N172 (N:172 ppm). After spheroidizing all samples have a main structure of ferrite.