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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/69227


    Title: 槽型配置與多道次回火堆銲之包藥電弧銲接製程應用於厚鋼板大型結構銲接:機械性能和冶金研究;Groove Configurations and multi-pass Temper Bead in Flux Cored Arc Welding Process Used in Thick Steel Plate Welds of Large Structures: Mechanical properties and Metallurgical Studies
    Authors: 凌國夏;Ling,Kuo-Hsia
    Contributors: 機械工程學系
    Keywords: 槽型配置;包藥銲線銲接;多道次銲接;衝擊韌性;回火堆銲;Groove configurations;Flux-cored arc welding;multi-pass welding;impact toughness;temper bead welding
    Date: 2015-09-18
    Issue Date: 2015-11-04 17:51:42 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 銲接用於船舶,橋樑,壓力容器,工業機械,汽車,機車車輛等諸多領域。與銲接相關的問題,亦在這些領域中出現。鋼的可銲接性與銲接熱影響區(HAZ)的最大硬度和銲道的冷裂紋敏感性有關。本研究利用包藥銲線電弧銲(FCAW)研究各種槽型的配置在機械式沖床建立銲接規範。研究以JIS SS400結構鋼銲接接頭在三種不同的凹槽構造的機械性能和冶金性能的影響。銲接接頭的機械性能在室溫下進行單軸拉伸實驗和夏比V型缺口衝擊測試(CVN)實驗。同時在多道次的銲接造成不同程度的熱處理,如回火或正常化發生在熱影響區,熱影響區中的不利微觀組織和再熱區可以通過上述過程使得熱影響區的韌性提高和硬度改善。實驗結果顯示,三種類型的槽型配置(C1,C和F), C1槽型具有的最大降伏強度(YS)和抗拉強度(UTS),同時F槽型在室溫測試具有最高的夏比V型缺口衝擊值。其主要原因可能為每個槽型構造的散熱特性。通過光學顯微鏡所顯示微觀組織特徵也表示不同的槽型配置在接頭有顯著影響因素。因此,可以藉由於散熱特性的變化來獲得不同程度的晶粒細化,得到各種機械性能和夏比衝擊衝擊性能。並進一步研究了回火堆銲(TBW)有兩種不同的銲接製程,即以4層4道次(4L4P)和4層10道次(4L10P)的影響。熱電偶固定到測量的熱循環,並沿著銲道中的溫度分佈曲線通過紅外線(IR)的圖像分析。在實驗之前全部銲接試片必須使用非破壞相控陣列超音波檢測(PAUT),檢查並確認試片必需無缺陷。夏比衝擊試驗在20和-20℃下完成,微硬度在室溫下進行量測。所述銲接過程中發現4層4道的製程。並透過光學顯微鏡(OM)分析,在回火熱影響區(HAZ)可以改善銲接接頭的衝擊韌性。此外,研究發現,在4層4道銲接製程中產生的整體硬度比4層10道銲接製程較低。;Ships, bridges, pressure vessels, industrial machinery, automobile, rolling stock and many other fields are all produced by welding technology. The common problem in these fields is associated with welding process. The maximum hardness of the heat affected zone (HAZ) and the cold cracking susceptibility of welds are results in Weldability of steel. This paper utilized a flux-cored arc welding (FCAW) technique and investigated various groove configurations as well as multi-pass welding sequences to create welding specifications in the mechanical press industry. Experimental investigations were conducted to examine the influence of three different groove configurations of JIS SS400 structural steel welded joints on mechanical and metallurgical properties. Mechanical properties of the welded joints were evaluated by uniaxial tensile testing and Charpy V-notch (CVN) impact testing at room temperature. Simultaneously after a multi-pass welding sequence, various degrees of thermal treatments such as tempering or normalization inevitably occur in the heat affected zone (HAZ). The unfavorable microstructures in the HAZ and reheated zones can be intentionally modified via the above procedure such that the toughness and microhardness of the HAZ improves. The experimental results revealed that of the three types of groove configurations (C1, C and F), groove type C1 possessed the maximum yield strength (YS) and ultimate tensile strength (UTS) while groove type F possessed the highest CVN values tested at room temperature. The fundamental reason may be attributed to heat dissipation characteristics of each groove configuration and associated exertion of the multi-pass welding sequence. Microstructural and morphological features as revealed through an optical microscope also indicate a significant influential factor of these joints among the different groove configurations. Therefore, grain refinement of varying degrees can be obtained due to the variation of thermal characteristics of heat input/dissipation and thus, various mechanical and CVN impact properties can be obtained. It further examined the effects of temper bead welding (TBW) made with two different welding processes, namely with 4 Layers 4 Passes (4L4P) and 4 Layers 10 Passes (4L10P). Thermocouples were fixed to measure the thermal cycles, and the temperature distribution curves along the weld seams were measured by Infrared Radiation (IR) images. All welded samples were checked using nondestructive Phased Array Ultrasonic Testing (PAUT) to ensure defect-free samples before the experiments commenced. The Charpy impact tests were finished in 20 and -20°C respectively. Vickers microhardness measurement was carried out at room temperature. The 4L4P welding process was found to improve the impact toughness of the welding joints. In addition, it was found that the 4L4P welding process produced an overall lower hardness than the 4L10P welding process.
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