利用鋼中內生的介在物誘導針狀肥粒鐵 ( Acicular Ferrite ) 是提昇鋼種強度和韌性的重要方法。含鎂介在物具有高熔點、細小分散的特性，通過鎂對鋁脫氧鋼進行改質，提昇鋼液純淨度的同時，利用所生成的介在物來改善鋼鐵的韌性及焊接性能。
本研究結合了最新一代的鎂氧化物冶金以及誘導基地組織產生針狀肥粒鐵的概念，尋找 SS400 低碳鋼種於連鑄製程後的熱處理路徑，透過提昇鋼鐵中針狀肥粒鐵所占有的比例，改善鋼鐵的韌性。實驗過程以物理模擬方式使用小型試片取代傳統上依賴經驗累積的實驗方法，分析位移式相變態溫度區間中持溫溫度以及冷卻速度對針狀肥粒鐵形成的影響；透過基地組織分析、微組織介在物分析、性質測試等方式探討針狀肥粒鐵與鎂基複合介在物之間關係，制定最佳的熱軋、熱處理製程。
結果顯示以 20 °C / s 冷卻至450 °C 持溫的試片基地相含有 44 ％ 的針狀肥粒鐵組織，於 0 °C 下韌性較不含有針狀肥粒鐵的試片提高12.4 倍。 SEM照片發現了針狀肥粒鐵於 5 μm含鎂介在物上成核的證據，此類介在物周圍並沒有貧錳區的形成，其誘導針狀肥粒鐵成核機制尚有待討論。

In order to study the function of Mg-based inclusions on acicular ferrite forming and the influence of acicular ferrite on toughness in low carbon commercial steel, the heat treatment simulation was carried out on Gleeble-1500 in Al-killed low carbon steel (SS400) with Mg treatment. 7 ppm Magnesium was wire-fed into SS400 low-carbon steel in a tank degasser to fine-tune the composition of the steel and obtain fine particles. Microstructure of the steel after different heat treatment processes between 1300 °C and 400 °C were studied through OM, SEM, and EBSD. It was found that Mg-based complex inclusions could act as the nucleation sites of acicular ferrite. EBSD analysis shows that the ratio of acicular ferrite in the specimen after 20 °C / s cooling from 1300 °C to 450 °C was 44%. The toughness of this steel has raised 12.4 times compared to the one without acicular ferrite. EDS mapping shows that the Mn-depleted zone didn’t appear around this kind of inclusions, the proper mechanism of inducing acicular ferrite for magnesium- based inclusions need further discussion.

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