本文選題：E690高強(qiáng)鋼　切入點(diǎn)：焊接接頭　出處：《北京科技大學(xué)》2015年博士論文

【摘要】：本文圍繞E690鋼及焊接接頭在含硫海洋薄液環(huán)境中的應(yīng)力腐蝕(SCC)行為和機(jī)理,根據(jù)真實(shí)焊接接頭熱影響區(qū)(HAZ)的組織制備了焊接熱模擬組織,并采用恒應(yīng)變U型彎試樣和慢應(yīng)變速率拉伸(SSRT)實(shí)驗(yàn)方法對(duì)比研究了E690鋼母材以及三種典型HAZ熱模擬組織在含硫海洋薄液環(huán)境中的SCC行為,對(duì)比分析了不同組織的SCC敏感性和開裂機(jī)理,并采用SSRT方法研究了硫含量和彈塑性預(yù)應(yīng)變對(duì)E690鋼在含硫海洋薄液環(huán)境中SCC行為的影響。最后通過SSRT實(shí)驗(yàn)方法,結(jié)合焊接接頭不同微區(qū)組織的力學(xué)和電化學(xué)性能分析,研究了E690鋼真實(shí)焊接接頭在模擬SO2污染海洋大氣薄液膜中的應(yīng)力腐蝕行為與機(jī)理。結(jié)果表明,E690鋼在含硫海洋薄液環(huán)境中的腐蝕產(chǎn)物由α-FeOOH. γ-FeOOH、β-FeOOH、Fe3O4、FeOCl組成,隨著試驗(yàn)周期的延長,銹層中α-FeOOH的相對(duì)含量不斷增加,同時(shí)Cr, Ni合金元素在內(nèi)銹層發(fā)生富集,進(jìn)而促進(jìn)了銹層的致密化,導(dǎo)致銹層底部產(chǎn)生氯離子的濃聚,促進(jìn)點(diǎn)蝕與應(yīng)力腐蝕裂紋的萌生,因而E690鋼在含硫海洋薄液環(huán)境中具有較大的應(yīng)力腐蝕敏感性,應(yīng)力腐蝕機(jī)理為陽極溶解和氫脆的混合機(jī)制,開裂模式為穿晶開裂。采用熱處理方法制備的焊接熱模擬組織可以較好的模擬焊接熱影響區(qū)的典型組織,母材和焊接熱模擬組織在模擬8O2污染海洋大氣環(huán)境中均具有很高的SCC敏感性,母材、細(xì)晶、粗晶、兩相組織在這種環(huán)境中的SCC敏感性依次增大；母材和粗晶組織的開裂模式為穿過板條貝氏體的穿晶開裂(TG-SCC),細(xì)晶和兩相組織為沿著M-A島與基體界面開裂的沿晶開裂模式(IG-SCC)。海洋大氣中的S02可通過促進(jìn)α-FeOOH的生成和Cr、Ni合金元素在內(nèi)銹層中的富集而促進(jìn)銹層的致密化,導(dǎo)致Cl-在銹層底部的濃聚和酸化,從而顯著促進(jìn)SCC裂紋的萌生與擴(kuò)展,因而增加了其應(yīng)力腐蝕敏感性：SO2對(duì)海洋薄液環(huán)境中的應(yīng)力腐蝕具有雙重作用：在腐蝕初期可促進(jìn)SCC裂紋的萌生；后期又通過致密銹層的形成抑制基體的腐蝕和應(yīng)力腐蝕開裂。應(yīng)力應(yīng)變可同時(shí)促進(jìn)E690鋼在海洋含硫環(huán)境中的陽極過程和陰極析氫反應(yīng),因而大大促進(jìn)了腐蝕和應(yīng)力腐蝕進(jìn)程;E690鋼在含硫薄液環(huán)境中一定彈塑性預(yù)變形條件下經(jīng)過4d后即會(huì)產(chǎn)生SCC微裂紋的萌生,且SCC微裂紋沿著原始奧氏體晶界形核；在含硫薄液中不同彈塑性預(yù)變形狀態(tài)下保持4d后,其SCC敏感性隨著彈塑性預(yù)變形量的增加而升高,特別是在塑性預(yù)變形條件下暴露一定時(shí)間后,其SCC敏感性大大增加。E690鋼焊接接頭在含硫薄液環(huán)境中具有較高的SCC敏感性,應(yīng)力腐蝕機(jī)制為陽極溶解和氫脆的混合機(jī)制。臨界熱影響區(qū)(ICHAZ)由于較低的強(qiáng)度、較負(fù)的腐蝕電位和較高的腐蝕電流密度以及M-A島的存在,而成為焊接接頭最薄弱的部位,ICHAZ區(qū)中的M-A島通過應(yīng)力集中效應(yīng)、微電偶腐蝕效應(yīng)以及氫脆效應(yīng)三者的協(xié)同作用對(duì)應(yīng)力腐蝕行為產(chǎn)生不利影響,共同促進(jìn)SCC裂紋沿M-A島與鐵素體基體的界面開裂。
[Abstract]:This paper focuses on E690 steel and welded joint in the marine environment in the thin liquid sulfur stress corrosion cracking (SCC) behavior and mechanism, according to the joint of the heat affected zone (HAZ) of the real welding organization prepared by thermal simulation and microstructure of welding, using constant strain type U bend test and slow strain rate tensile (SSRT) test method a comparative study of the E690 steel base material and three kinds of typical HAZ thermal simulation SCC behavior in thin liquid sulfur marine environment, a comparative analysis of SCC sensitivity and cracking mechanism of different tissues, studied the effect of sulfur content and the elastoplastic pre strain of E690 steel in marine environment SCC thin liquid sulfur behavior and the the SSRT method. Finally, by the method of SSRT analysis of welding joints with different micro structure mechanical and electrochemical properties of E690 steel were studied real welded joint stress corrosion behavior and mechanism of SO2 in the simulation of marine pollution in the atmosphere of thin film. Show that the corrosion of E690 steel in marine environment in thin liquid sulfur by -FeOOH. gamma alpha -FeOOH, beta -FeOOH, Fe3O4, FeOCl, along with the extension of the test cycle, the relative content of rust layer of alpha -FeOOH increased, while Cr, Ni, the rust layer of alloy elements enriched, and then promote the densification of the rust layer the resulting rust layer at the bottom of the chloride ion concentration, and promote the pitting initiation of stress corrosion cracking of E690 steel, and has greater sensitivity to stress corrosion in the marine sulfur thin liquid environment, the mechanism of the stress corrosion mechanism for hybrid anodic dissolution and hydrogen embrittlement, the cracking mode is transgranular cracking. By heat treatment the preparation methods of the welding thermal simulation can better welding typical microstructure of heat affected zone and base metal and welding thermal simulation organization has the sensitivity of SCC is high in 8O2 simulation of marine pollution in the atmospheric environment of parent material, fine grain, coarse grain, two-phase The sensitivity of SCC organization in this environment increases; the cracking mode of base material and coarse grain structure for the lath bainite transgranular cracking (TG-SCC), fine grain and phase organization mode of M-A along the island and the interfacial crack intergranular cracking (IG-SCC). In the marine atmosphere can promote S02 generation and Cr alpha -FeOOH, Ni, enrichment of alloy elements in the rust layer and promote the densification of the rust layer, resulting in Cl- accumulation and acidification of the bottom of the rust layer, which improved SCC crack initiation and expansion, thus increasing the stress corrosion sensitivity: has the dual role of stress corrosion of SO2 on the sea the thin liquid in the environment: in the early stages of corrosion can promote SCC crack initiation; later by the rust layer on corrosion inhibition of substrate and stress corrosion cracking. Stress strain can also promote the anodic process of E690 steel in marine environment and Yin sulfur Polar hydrogen evolution reaction, and the corrosion and stress corrosion process greatly promote initiation of E690 steel in sulfur; thin liquid environment in elastoplastic pre deformation condition after 4D SCC will lead to micro cracks, and SCC micro cracks along the original austenite grain boundary nucleation; keep the 4D in different elastic thin liquid sulfur plastic pre deformation condition, the sensitivity of SCC increased with the increasing of elastoplastic pre deformation, especially to spend some time in the pre plastic deformation condition, the sensitivity of SCC greatly increased the welded joints of.E690 steel SCC has a high sensitivity in thin liquid sulfur environment, stress corrosion mechanism is mixed the mechanism of anodic dissolution and hydrogen embrittlement. The critical heat affected zone (ICHAZ) due to the low strength, low corrosion potential and high corrosion current density and the presence of a M-A Island, and become the weakest part of the welding joint in the ICHAZ area of M-A island. The synergistic effect of the three synergies between the micro couple corrosion effect and the hydrogen embrittlement effect has an adverse effect on the stress corrosion behavior, which promotes the SCC crack propagation along the M-A Island interface with ferrite substrate.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG172.9

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 王炳英;霍立興;張玉鳳;王東坡;;X80管線鋼焊接接頭SSCC研究及數(shù)值模擬[J];焊接學(xué)報(bào);2007年01期

，

本文編號(hào)：1668421