本文選題：低合金高強度耐候鋼 + 熱處理　； 參考：《南京航空航天大學(xué)》2017年碩士論文

【摘要】：高強度低合金耐候鋼是高強度低合金鋼板(HSLA)研究和應(yīng)用發(fā)展的重要方向,研究開發(fā)出既具有好的綜合力學(xué)性能又具備優(yōu)良耐蝕性能的低合金高強度耐候鋼具有重要而緊迫的意義。本文采用光學(xué)顯微鏡(OM)、掃描電鏡(SEM)及能譜儀(EDS)、X射線衍射儀(XRD)、拉伸試驗、浸泡試驗、電化學(xué)測試等多種分析手段,研究了熱處理及Cr、Ni元素對低合金高強度耐候鋼組織、性能及在3.5%NaCl溶液中腐蝕行為的影響規(guī)律,得到的主要結(jié)論為:對熱軋、退火及正火態(tài)Q500H耐候鋼進行組織和耐蝕性能分析,結(jié)果表明:熱軋、退火及正火都得到珠光體和鐵素體組織,其中熱軋鋼晶粒最粗大,其次退火鋼和正火鋼。極化曲線測得的熱軋、退火及正火態(tài)裸鋼的自腐蝕電流密度依次升高,分別為0.4418×10-5A·cm-2,0.7364×10-5A·cm-2,1.064×10-5A·cm-2,電化學(xué)阻抗譜測得的試樣電荷轉(zhuǎn)移電阻值依次降低。試樣浸泡5個月去除腐蝕產(chǎn)物后熱軋鋼基體表面腐蝕坑最細小,腐蝕程度最低,正火鋼腐蝕程度最大。熱軋態(tài)耐候鋼銹層由鐵的羥基氧化物α-FeOOH,β-FeOOH,γ-FeOOH及鐵的氧化物Fe3O4組成。截面掃描形貌觀察到熱軋鋼銹層最薄最致密,正火鋼最厚最疏松。失重實驗測得熱軋鋼年腐蝕速率最小,其次退火鋼,正火鋼最大。對熱軋態(tài)Q500H及Q700H低合金耐候鋼進行組織和耐蝕性能分析,結(jié)果表明:試樣組織為珠光體和鐵素體,Cr在兩相中均勻分布,Ni在鐵素體相中含量更多。Cr、Ni含量較高的Q700H鋼年腐蝕速率為0.1068 mm/y,比Q500H鋼減少了4.4%。浸泡60天后,試樣自腐蝕電流密度增加,與Q500H耐候鋼相比,Q700H耐候鋼仍具有較高的電荷轉(zhuǎn)移電阻值和較低的自腐蝕電流密度。浸泡5個月的Q700H鋼試樣表面腐蝕坑更細小。兩種熱軋態(tài)耐候鋼銹層成分相同,Cr、Ni的增加促進了α-FeOOH及Fe3O4的生成。浸泡5個月后Cr、Ni在銹層內(nèi)富集,Cr集中在內(nèi)銹層,Ni富集于基體和銹層界面處,Cr、Ni含量越多,富集越明顯,銹層越致密。對控軋控冷態(tài)Q500H及Q700H低合金高強度耐候鋼進行組織和性能分析,結(jié)果表明:Cr、Ni含量的增加顯著提高了耐候鋼的拉伸強度,屈服強度從Q500H耐候鋼的585 MPa增加到Q700H耐候鋼的749 MPa。與Q500H耐候鋼相比,Cr、Ni含量較高的Q700H裸鋼具有較低的自腐蝕電流密度和較高的電荷轉(zhuǎn)移電阻值。兩種鋼銹層組成成分相同,Cr、Ni含量的增加使銹層中穩(wěn)定相Fe3O4含量提高。腐蝕浸泡前10d,Cr、Ni含量的增加促進了Q700H鋼銹層的連續(xù)性,增強了銹層對基體的保護能力;試樣浸泡5個月后,合金元素含量高的Q700H鋼中Cr、Ni元素在銹層和基體的界面處富集更明顯,銹層和基體結(jié)合更緊密,年腐蝕速率降低。
[Abstract]:High strength low alloy weathering steel is an important direction in the research and application of high strength low alloy steel plate. It is important and urgent to develop low alloy high strength weathering steel with good comprehensive mechanical properties and excellent corrosion resistance. In this paper, the microstructure of low alloy high strength weathering steel was studied by means of optical microscope, scanning electron microscope (SEM), energy spectrometer (EDS) X ray diffractometer, tensile test, immersion test, electrochemical test and so on. The main conclusions are as follows: the microstructure and corrosion resistance of hot rolling, annealing and normalizing Q500H weathering steel are analyzed. Pearlite and ferrite were obtained by annealing and normalizing, among which hot rolled steel had the thickest grain size, followed by annealed steel and normalizing steel. The self-corrosion current density of hot-rolled, annealed and normalizing bare steels was increased by polarization curve, which was 0.4418 脳 10 -5A cm ~ (-2), 0.7364 脳 10 ~ (-5A) cm ~ (-2), 1.064 脳 10 ~ (-5A) cm ~ (-2), respectively, and the charge transfer resistance of sample was decreased by electrochemical impedance spectroscopy. After immersion for 5 months, the surface corrosion pit of hot rolled steel was the smallest, the corrosion degree was the lowest, and the corrosion degree of normalizing steel was the largest. The rust layer of hot rolled weathering steel consists of hydroxyl oxides 偽 -FeOOH, 尾 -FeOOH, 緯 -FeOOH and Fe3O4 of iron. The section scanning morphology shows that the rust layer of hot rolled steel is the thinnest and the densest and the thickest and most loose of normalizing steel. The annual corrosion rate of hot rolled steel is the lowest, followed by annealed steel and normalizing steel. The microstructure and corrosion resistance of hot-rolled Q500H and Q700H low-alloy weathering steels were analyzed. The results show that the corrosion rate of Q700H steel with higher content of Ni in ferrite phase and pearlite and ferrite in the two phases is 0.1068 mm / yy, which is 4.4mm / yr less than that of Q500H steel. The results show that the corrosion rate of Q700H steel is 0.1068 mm / yr, which is less than that of Q500H steel, and the corrosion rate of Q700H steel is higher than that of Q500H steel. Compared with Q500H weathering steel, Q700H weathering steel has higher charge transfer resistance and lower corrosion current density than Q500H weathering steel. The surface corrosion pits of Q700H steel samples soaked for 5 months were smaller. The formation of 偽 -FeOOH and Fe3O4 was promoted by the increase of the same composition of rust layer of two hot rolled weathering steels. After soaking for 5 months, Cr and Cr are concentrated in the rust layer. The more the content of Cr and Ni is at the interface between the matrix and the rust layer, the more obvious the enrichment is, and the denser the rust layer is. The microstructure and properties of controlled rolling controlled cold Q500H and Q700H low alloy high strength weathering steels were analyzed. The results showed that the tensile strength of weathering steels increased significantly with the increase of the content of 1: Cr-Ni, and the yield strength increased from 585 MPa of Q500H weathering steels to 749MPa of Q700H weathering steels. Compared with Q500H weathering steel, Q700H bare steel with higher Cr-Ni content has lower corrosion current density and higher charge-transfer resistance. The content of Fe3O4 in the stable phase increases with the increase of the same composition of the two kinds of steel rusts. The increase of Cr-Ni content 10 days before corrosion soaking promoted the continuity of rust layer of Q700H steel, and enhanced the protective ability of rust layer to matrix, and after 5 months of immersion, the enrichment of Cr-Ni element in Q700H steel with high alloy element content was more obvious at the interface between rust layer and matrix. The corrosion rate of the rust layer is decreased with the combination of the rust layer and the substrate.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG178

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