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Title: 控制軋延加速冷卻製程鋼構之微觀組織與銲接性研究---子計畫IV:TMCP銲件疲勞特性研究(III)
Fatigue Crack Growth of TMCP Steel Weldments (III)
Authors: 蔡履文
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: 控制軋延加速冷卻鋼板(TMCP鋼板);疲勞性質;疲勞裂縫成長;熱影響區
Thermomechanical control processed steel (TMCP steel);Fatigue property;Fatigue crack growth;Heat-affect zone
Date: 1997-08
Issue Date: 2011-06-28T07:09:11Z
Publisher: 行政院國家科學委員會
Abstract: 本研究為針對API 5L-X65 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,其原因可歸咎於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,粗晶熱影響區主要為上、下變韌鐵混合組織,細晶熱影響區主要為微細肥粒鐵和波來鐵的混合組織。衝擊試驗的結果顯示,滾軋方向對衝擊值的影響並不明顯。熱影響區有最高的衝擊值。而銲道的衝擊值卻是最低的。實驗應力之比值(R)對鋼材疲勞裂縫成長速率的影響是輕微的。銲道相對於母材,有明顯較高的曲線斜率。將鋼材及銲件於飽和硫化氫水溶液浸泡24小時後,進行疲勞裂縫成長試驗,均顯示在低.DELTA.K範圍均有較高之裂縫成長速率。
The microstructures and fatigue crack growth rates (FCGRs) of TMCP steel 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 the mixture of lower and upper bainite. Fine-grained HAZ consists of mainly refined ferrite and pearlite mixed structures. The results of Charpy impact tests reveal the effect of rolling direction on the impact energy is not obvious. HAZ has the highest impact values among the specimens in contrast to the lowest impact values for the weldmetal. The effect of R ratio on the fatigue crack growth rates (FCGRs) for the steel plate in minor. The fusion zone shows a significantly higher Paris-law gradient than the steel plate. All the specimens after immersion in saturated H/sub 2/S solution for 24 hours, higher FCGRs in the low .DELTA.K ranges are observed throughout the tests.
Relation: NSC87-2216-E019-008
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/9445
Appears in Collections:[Institute of Materials Engineering] Research Reports

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