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題名 | 熱處理對高入熱量電渣銲接TMCP結構鋼板機械性質與顯微組織之影響=Heat Treatment Influence on the Mechanical Property and Microstructure in High Heat Input Electro-Slag Welds of TMCP Steel Plate |
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作者 | 林英志; Lin, Yin-chih; |
期刊 | 高雄科學技術學院學報 |
出版日期 | 19981200 |
卷期 | 28 1998.12[民87.12] |
頁次 | 頁115-137 |
分類號 | 440.365 |
語文 | chi |
關鍵詞 | TMCP結構鋼板; 高入熱量電渣銲接; 機械性質; 顯微組織; TMCP structural steel plate; High heat input ESW; Mechanical property; Microstructure; |
中文摘要 | 50mm厚熱機軋延鋼板(The-mechanically controlled process-TMCP steel plate) , 以高入熱量電渣銲接 (ESW) 後, 銲道出現三種不同主要顯微組織; (1) 不整形肥粒鐵 (allotriomorphic ferrite- α ), (2) 費德曼肥粒鐵 (Widmanstatten ferrite- α w ) , (3) 針狀肥粒鐵 (acicular ferite- α a ),銲道優異的韌性歸因於銲道針狀肥粒鐵的 交叉排列分佈, 將大的沃斯田鐵晶粒分切成許多細小交叉的針狀肥粒鐵晶區, 進而阻折 (deflection) 裂痕的延佈,而使銲道韌性獲得最佳的結果。 銲道針狀肥粒鐵類似下變韌鐵 組織,不同的是銲道針狀肥拉鐵內η碳化物的析出方向是平行於銲道針狀肥粒鐵晶軸劈開面 (habit plane) , 由於η碳化物的析出, 使得銲道針狀肥粒鐵發生整合應變 (coherent strain),因而提高了銲道針狀肥粒鐵的強度與韌性,η碳化物為斜方晶結構 (onhorhombic crystal structure) , 其晶格常數 (lattice parameter) 為 a=4.704A, b=4.318A, c=2.830A, 析出相η碳化物與針狀肥粒鐵兩者的結晶方向關係 (orientation relationships) 為 [2 4 4 ] η //[1 1 3 ] α a, [0 1 0] η //[0 1 2] α a, [2 2 0] η //[ 1 3 3] α a。TMCP 構鋼板高入熱量電渣銲接後,熱影響區發生晶粒粗大化及產 生費德曼肥粒鐵組織,銲接時添加微量的鈦 (Ti) 鈮 (Nb) 元素,對銲道韌性的提升毫無幫 助,反而促使銲件銲道變脆。TMCP 結構鋼板,高入熱量電渣銲接後,施以 900 ℃╱ 25 分 退火熱處理,則可以去除銲道三種主要肥粒鐵顯微組織,而使銲道與母材的顯微組織一致、 機械性質一致。 |
英文摘要 | After high heat input electro-slag welding (ESW) of a thickness 50 mm thermo-mechanically controlled process (TMCP) steel plate, the primary microstructures in the weld deposit can be categorised into three morphologies; (1) allotriomorphic ferrite - α, (2)Widmanstatten ferrite - α w,, (3) acicular ferrite - α a. The optimal Charpy toughness of the weidment is ascribed to the cross distribution of the acicular ferrite that partitions the largeaustenite grain to many acicular cross ferrite grains. The acicular ferrite deflects the cracks during the process of fracture, and enhances the weidment to achieve the optimal toughness. The acicular ferrite in weld is similar to the lower bainite, but the difference is within the acicular ferrite that ther) carbide precipitates parallel to the acicular ferrite's habit plane. Due to η carbide precipitate within the acicular ferrite, there exists the coherent strain in the acicular ferrite which enhances the strength and toughness of the acicular ferrite of the weidment. η carbide has an orthorhombic crystal structure, with lattice parameter of a = 4.704 A, b = 4.318 A, c= 2.830 A. The orientation relationships between the precipitate η carbide and acicular ferrite are determined to be [ 2 4 4 ] η // [ 1 1 3 ], [0 1 0] η [0 1 2] α a, and [ 2 2 0] η // [ 1 3 3 ] α a, respectively. In high heat input electro-slag welding (ESW) of a TMCP steel plate, the coarse grain growth as well as the Widmanstatten ferrite - α w will be generated in the heat-affected zone (trace Ti, Nb elements during the ESW process is not useful in increasing Charpy toughness of the weidment. On the contrary, it will make a brittle weidment. After high heat input electro-slag welding (ESW) of a TMCP steel plate, the primary three ferrite microstructures in the weidment can be eliminated by using of 900 ℃ /25 min. annealing treatment, for which the weld and the base metal of the TMCP steel plate will have the same r@icrostructure and the same mechanical property. |
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