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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/9437

Title: 控制軋延加速冷卻製程鋼構之微觀組織與銲接特性研究---子計畫IV:TMCP銲件之疲勞特性研究(II)
Fatigue Crack Growth of TMCP Steel Weldments(II)
Authors: 蔡履文
Contributors: NTOU:Institute of Materials Engineering
Keywords: 溫度控制過程;控制軟延;氧化鈦;金相觀察
Temperature control process;Controlled rolling;Titanium oxide;Metallography observation
Date: 1996-08
Issue Date: 2011-06-28T07:09:10Z
Publisher: 行政院國家科學委員會
Abstract: 本研究為針對TMCP鋼材及銲件,探討其顯微組織與疲勞裂縫成長特性之關係。實驗結果顯示:直銲銲件之熱影響區僅呈現些微硬化,其原因可歸究於TMCP鋼材之低碳當量,因此TMCP銲件將有較高之韌性。觀察銲件之顯微組織,粗晶熱影響區由大部分為下變韌鐵及些許上變韌鐵所組成。熱影響區細晶區為細化之變韌鐵及肥粒鐵並在板條狀邊界夾雜微結構相。雖然板材依滾軋方向做不同方向之取裁,呈現高衝擊韌性方向性,但滾軋方向對TMCP鋼材之疲勞裂縫成長特性僅有些許影響。不論銲件是否經600.degree.C/2hr銲後回火處理,銲件熱影響區疲勞裂縫成長速率均比原始板材為低。熱影響區變韌鐵組織,比原始鋼材肥粗鐵及波來鐵混合組織有較高之韌性,而導致熱影響區有較原始鋼材為低之裂縫成長速率。整體來說,經銲後回火之TMCP銲件,於不同區域均顯示較原始鋼材為佳之疲勞特性。<
The microstructures and fatigue crack growth rates (FCGRa) of EH36 TMCP steel base plates and welds were investigated. A minor increase in hardness in the as-welded heat affected zone (HAZ) can be attributed to the low carbon equivalent (CE) of the steel. Hence, the improvement in the HAZ toughness of the weld, as compared to the traditional hardened steel weld, can be anticipated. Microstructural observations indicate the coarse-grained HAZ is composed of a large amount of lower bainite with some upper bainite. Fine-grained HAZ consists of refined ferrite and bainite, together with interlath microphases. Although there is an obvious different impact energy values for L and T specimens, the effect of orientation and tempering treatment only has a slight influence on the FCGRs of the TMCP steel plate, as compared the data obtained from LT, TL and tempered specimens. The lower FCGRs of the HAZ than those of the steel base plate, regardless of the post-weld heat treatment (PWHT), can be attributed to the formation of low-carbon bainite with high toughness, instead of ferrite and intergranular pearlite in the steel plate. The as-welded fusion zone in a CW specimen shows a significantly high Paris-law gradient. The evidence shows that the TMCP steel weld after tempering at 600.degree.C for 2 hr possesses a slightly better resistance to crack growth than the steel plate.
Relation: NSC86-2216-E019-008
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/9437
Appears in Collections:[材料工程研究所] 研究計畫

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