不同鑄造方式對於AISI 420不銹鋼微結構與機械性質之影響

本研究藉著不同的鑄造方式與持溫時間，比較其對AISI 420不銹鋼微結構與機械性質之影響，微結構的探討包含晶粒大小、碳化物析出與破壞分析；機械性質差異之比較方面，如硬度、衝擊值、抗拉強度、斷面收縮率與伸長率等，此外，同時進一步探討微結構組織產生之差異，對於機械性質所造成之影響。 AISI 420不銹鋼鑄錠是採用瑞典Uddeholm公司製造之預熔合金顆粒(Granshot)，其鑄件之製備係使用高週波熔煉爐，於一般大氣條件下進行。每一爐次加入7公斤之原始塊材，待溫度升至1700°C後開始進行持溫，持溫時間為1分鐘、10分鐘與30分鐘，並分別澆鑄於金屬模與乾砂模，鑄造凝固完成後之鋼錠，使用退火調質，再依流動方向取樣；接著進行淬火與低溫回火處理，藉以探討不同鑄造方式與持溫時間對於AISI 420不銹鋼顯微結構與機械性質之影響。實驗結果顯示，AISI 420不銹鋼鑄造方法需在一定的熔融高溫下(1700°C)，以提供金屬液凝固所需之驅動力，原始鑄錠的樹枝狀晶比率，隨持溫時間的增加而上升。較長持溫時間(30分鐘)的乾砂模鑄錠，經過熱處理後具有較佳的衝擊韌性，平均的衝擊值由7.63 J提升至14.3 J；相反地，由於較快的冷卻速率，較長持溫時間(30分鐘)的金屬模鑄件，經過熱處理後其衝擊值反而由5.77 J下降至2.93 J，顯示持溫時間的增加，對金屬模鑄件的韌性並沒有幫助。

關鍵字

鑄造； AISI 420不銹鋼；衝擊值；預熔合金顆粒；退火；淬火；低溫回火

並列摘要

This study compared various casting processes and soaking times on the microstructural and mechanical properties of AISI 420 stainless steel. The main discussions on microstructure included: grain size, carbide precipitation and failure analysis. The mechanical properties of hardness, impact and tensile tests were investigated, and elongation and reduction area inspections were performed. In addition, the effects on the mechanical properties of AISI 420 casting steel for different microstructures were also studied. In the research, the ingot of AISI 420 stainless steel used the granshot which was obtained from Sweden’s Uddeholm Company. The casts were produced by a high-frequency reaction melting furnace at an atmosphere condition. We usually added 7 kg of 420 granshot to the furnace and increased the melting temperature to 1700°C. The soaking time was kept at 1, 10 and 30 min. Meanwhile, the molten casting was formed into the different metal and epoxy resin patterns, respectively. When the castings had solidified, the specimens were cut and removed from the flow direction of the castings after the annealing process. Finally, the quenching and low-temperature tempering treatments were performed in order to investigate the various casting processes and soaking times on the microstructural and mechanical properties of AISI 420 stainless steel. The experimental results showed that AISI 420 stainless steel casting required a higher melting temperature (1700°C) to provide the driving force of solidification. Increasing the soaking time of the original 420 casting resulted in a higher dendrite rate. Furthermore, the optimal impact toughness of the 420 casting was obtained by the longer soaking time (30 min) of the epoxy resin patterns after heat treatment. The average value of impact energy of 7.63 J increased to 14.3 J. Conversely, the fast cooling rate resulted in poor toughness. The lowest impact energy of the 420 casting was obtained by the longer soaking time (30 min) of the metal pattern after heat treatment. The impact energy of 5.77 J was decreased to 2.93 J. This showed that increasing the soaking time of the metal pattern did not enhance the toughness of AISI 420 stainless steel.

並列關鍵字

Casting ； AISI 420 Stainless Steel ； Impact ； Granshot ； Annealing ； Quench and Low-temperature Tempering

參考文獻

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[53] 楊國和洪敏雄，鑄造手冊(第二冊)，台北市：中華民國鑄造學會，1997，第297頁。

[1] Çetin, Z. Tek, A. Öztarhan and N. Artunç, "A comparative study of single and duplex treatment of martensitic AISI 420 stainless steel using plasma nitriding and plasma nitriding-plus-nitrogen ion implantation techniques," Surface and Coatings Technology, vol. 201, 2007, pp. 8127–8130.

[2] W. Tuckart, E. Forlerer and L. Iurman, "Delayed cracking in plasma nitriding of AISI 420 stainless steel," Surface and Coatings Technology, vol. 202, 2007, pp. 199–202.

[3] Yun-tao Xi, Dao-xin Liu and Dong Han, "Improvement of corrosion and wear resistances of AISI 420 martensitic stainless steel using plasma nitriding at low temperature," Surface and Coatings Technology, vol. 202, 2008, pp. 2577–2583.

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不同鑄造方式對於AISI 420不銹鋼微結構與機械性質之影響

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