低合金高强度耐候钢的腐蚀性能研究

发布时间：2018-04-30 12:46

本文选题：低合金高强度耐候钢 + 热处理　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：高强度低合金耐候钢是高强度低合金钢板(HSLA)研究和应用发展的重要方向,研究开发出既具有好的综合力学性能又具备优良耐蚀性能的低合金高强度耐候钢具有重要而紧迫的意义。本文采用光学显微镜(OM)、扫描电镜(SEM)及能谱仪(EDS)、X射线衍射仪(XRD)、拉伸试验、浸泡试验、电化学测试等多种分析手段,研究了热处理及Cr、Ni元素对低合金高强度耐候钢组织、性能及在3.5%NaCl溶液中腐蚀行为的影响规律,得到的主要结论为:对热轧、退火及正火态Q500H耐候钢进行组织和耐蚀性能分析,结果表明:热轧、退火及正火都得到珠光体和铁素体组织,其中热轧钢晶粒最粗大,其次退火钢和正火钢。极化曲线测得的热轧、退火及正火态裸钢的自腐蚀电流密度依次升高,分别为0.4418×10-5A·cm-2,0.7364×10-5A·cm-2,1.064×10-5A·cm-2,电化学阻抗谱测得的试样电荷转移电阻值依次降低。试样浸泡5个月去除腐蚀产物后热轧钢基体表面腐蚀坑最细小,腐蚀程度最低,正火钢腐蚀程度最大。热轧态耐候钢锈层由铁的羟基氧化物α-FeOOH,β-FeOOH,γ-FeOOH及铁的氧化物Fe3O4组成。截面扫描形貌观察到热轧钢锈层最薄最致密,正火钢最厚最疏松。失重实验测得热轧钢年腐蚀速率最小,其次退火钢,正火钢最大。对热轧态Q500H及Q700H低合金耐候钢进行组织和耐蚀性能分析,结果表明:试样组织为珠光体和铁素体,Cr在两相中均匀分布,Ni在铁素体相中含量更多。Cr、Ni含量较高的Q700H钢年腐蚀速率为0.1068 mm/y,比Q500H钢减少了4.4%。浸泡60天后,试样自腐蚀电流密度增加,与Q500H耐候钢相比,Q700H耐候钢仍具有较高的电荷转移电阻值和较低的自腐蚀电流密度。浸泡5个月的Q700H钢试样表面腐蚀坑更细小。两种热轧态耐候钢锈层成分相同,Cr、Ni的增加促进了α-FeOOH及Fe3O4的生成。浸泡5个月后Cr、Ni在锈层内富集,Cr集中在内锈层,Ni富集于基体和锈层界面处,Cr、Ni含量越多,富集越明显,锈层越致密。对控轧控冷态Q500H及Q700H低合金高强度耐候钢进行组织和性能分析,结果表明:Cr、Ni含量的增加显著提高了耐候钢的拉伸强度,屈服强度从Q500H耐候钢的585 MPa增加到Q700H耐候钢的749 MPa。与Q500H耐候钢相比,Cr、Ni含量较高的Q700H裸钢具有较低的自腐蚀电流密度和较高的电荷转移电阻值。两种钢锈层组成成分相同,Cr、Ni含量的增加使锈层中稳定相Fe3O4含量提高。腐蚀浸泡前10d,Cr、Ni含量的增加促进了Q700H钢锈层的连续性,增强了锈层对基体的保护能力;试样浸泡5个月后,合金元素含量高的Q700H钢中Cr、Ni元素在锈层和基体的界面处富集更明显,锈层和基体结合更紧密,年腐蚀速率降低。
[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 伪 -FeOOH, 尾 -FeOOH, 纬 -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 伪 -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.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG178

【参考文献】