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Corrosion Behavior of TMCP Steel and Its Weldment in Marine Environment(II)
|Contributors: ||NTOU:Institute of Materials Engineering|
TMCP steel plate;Heat affected zone (HAZ);Corrosion behavior;Corrosion prevention;Weldment
|Issue Date: ||2011-06-28T07:09:10Z
|Abstract: ||TMCP 鋼板被推薦應用於海洋結構物,船體結構,此鋼板除具高強度外因碳含量低之故而擁有高韌性及可銲性等優點。惟銲接製作結構物過程受銲道熔填金屬及熱循環作用影響母材之金相組織,造成銲道結構物材料本身局部不均勻性。本研究主要針對此TMCP鋼板銲接之銲道與銲道附近進行海水腐蝕性評估,包含利用直流電化學方式測試,並利用電化學氫滲透及氫原子微印技術來探討銲件之微觀組織對氫滲透之影響。< 實驗結果顯示,TMCP鋼材的晶粒比一般軋延狀態的鋼材細化,而且較不具軋延方向性。在動態電位極化測試的結果,低入熱量銲件熱影響區與銲道金屬接合處,其腐蝕電流較高。高入熱量潛弧銲位於銲道金屬熔填接合區域,腐蝕電流較大。腐蝕速率與銲接入熱量有關,而與試片厚度無關。交流阻抗頻譜法所得的結果母材有較佳之耐蝕性。< 由電化學氫滲透實驗發現:銲件之組織及晶粒粗細對氫原子之滲透及視固溶量皆有影響。由氫原子微印技術之實驗可知,氫原子在銲件內部之主要擴散路徑為晶界及夾雜物,亦即缺陷及能量較高之位置。<|
TMCP steels have been widely recommended to hull and off-shore structure applications. Because of their low carbon equivalent and low index of weld cracking susceptibility, TMCP steels are possessed of the good weldability and good fracture toughness. Since the solidified weld metal and the heat affected zone of base metal (BM) subjected to a thermal cycle during welding operation, they come up with an inhomogenuity in the weldments. The purpose of this study was to evaluate the corrosion behaviors of the weld metal and the HAZ in the seawater. Besides, a electrochemical permeation technique and a hydrogen microprint technique are performed to study the influence of microstructure on hydrogen transport in weldments.< The results show that the grain size of the TMCP steel is finer and with a less preferred orientation than that of the material received in an as-rolled condition. The results of dynamic polarization tests of the weldments show that the corrosion current is significantly higher at the interfacial region of WM/HAZ in low heat-input SMAW and FCAW process. However, the corrosion current is the greatest at the bottom junction of the double V-groove weld deposits in high heat input SAW process. The results also show that corrosion rate and the location of corrosion depends more on the welding heat input reveal to welding process and is independent on the plate thickness.< Base metal shows higher permeation rate and diffusivity than the weldments. By hydrogen microprint technique, a monolayer of AgBr emulsion was coated on a selected site of welded specimen to observe the hydrogen transport phenomena. It confirms that the main diffusion path and the trapping sites are the defects and high energy interface, for example grain boundary and ferrite/pearlite interface.<
|Appears in Collections:||[材料工程研究所] 研究計畫|
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