本文關(guān)鍵詞：X80管線鋼焊接接頭的微觀組織及耐蝕性研究　出處：《長安大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： X80管線鋼 焊接熱輸入 峰值溫度 顯微組織 耐蝕性

【摘要】：長距離管道運(yùn)輸過程中需經(jīng)過各種各樣的地質(zhì)環(huán)境,運(yùn)輸管線鋼面臨著腐蝕造成的一系列安全問題。在實(shí)際服役過程中,管線鋼的焊接接頭由于組織差異以及雜質(zhì)等因素的影響,最容易腐蝕而產(chǎn)生裂紋,而焊接應(yīng)力誘發(fā)裂紋擴(kuò)展容易造成腐蝕斷裂,從而導(dǎo)致嚴(yán)重后果。因此,本研究針對目前我國管道運(yùn)輸采用的X80管線鋼,對其焊接接頭的微觀組織、力學(xué)性能和腐蝕性能等進(jìn)行系統(tǒng)研究,從而為X80管線鋼焊接管線大規(guī)模長期應(yīng)用提供依據(jù)。本研究采用金相顯微鏡和掃描電鏡觀察焊縫、熱影響區(qū)和母材的微觀組織,分析焊接熱循環(huán)參數(shù)對熱影響區(qū)組織的影響。結(jié)果表明,峰值溫度為1350℃時(shí),隨著熱輸入的增大,貝氏體、鐵素體逐漸減少,粒狀貝氏體增多;隨著峰值溫度降低,組織逐漸由貝氏體、鐵素體及粒狀貝氏體轉(zhuǎn)變?yōu)閴K狀鐵素體。采用Gleeble-3500型熱模擬試驗(yàn)機(jī)研究了在不同焊接熱輸循環(huán)條件下X80管線鋼及其焊接熱影響區(qū)的硬度特征。研究結(jié)果表明,X80管線鋼的熱影響區(qū)粗晶區(qū)(CGHAZ)顯微硬度隨焊接熱輸入增大呈下降趨勢;熱影響區(qū)顯微硬度隨峰值溫度增大呈升高趨勢。采用了Autolab電化學(xué)工作站分別研究了在0.5 mol/L Na2CO3+1 mol/L NaHCO3腐蝕溶液中和5%NaCl+0.5%醋酸溶液中X80管線鋼母材、焊縫和熱影響區(qū)的耐蝕性。結(jié)果表明,熱輸入對CGHAZ的耐蝕性影響比較明顯,隨著熱輸入增加腐蝕速率減小,CGHAZ的耐腐蝕性能變好;在峰值溫度為較高的1350℃或者是較低的800℃時(shí),對應(yīng)的腐蝕速率較高;焊縫和熱影響區(qū)的腐蝕傾向遠(yuǎn)大于母材,耐蝕性均較差;X80管線鋼焊接接頭在酸性腐蝕液中的耐蝕性比在堿腐蝕液中差,但都會產(chǎn)生鈍化膜,在酸性腐蝕液中鈍化膜不穩(wěn)定。
[Abstract]:During the long distance pipeline transportation, the transportation pipeline steel is faced with a series of safety problems caused by corrosion. In the actual service process, the transportation pipeline steel faces a series of safety problems. The welded joints of pipeline steel are most likely to corrode due to the influence of different structure and impurity, while the welding stress induced crack propagation is easy to cause corrosion and fracture, which leads to serious consequences. In this study, the microstructure, mechanical properties and corrosion properties of welded joints of X80 pipeline steel used in pipeline transportation in China were studied systematically. In this study, the microstructure of weld, heat-affected zone and base metal was observed by metallographic microscope and scanning electron microscope. The effect of welding thermal cycle parameters on the microstructure of HAZ is analyzed. The results show that the bainite, ferrite and granular bainite decrease with the increase of heat input at the peak temperature of 1350 鈩，

本文編號：1359931