天然气长输管道腐蚀特性及控制对策

1 前言在不同地质土壤环境中钢制埋地长输管道外腐蚀机理、成因、形态及特征经国内外防腐界数十年研究及工程应用实践已基本为人们所认识。并在此基础上 ,制定了相关管道外防腐技术对策及设计、作业标准 ,形成了多种外防腐涂层复合电化学保护的防腐蚀技术体系。管道腐蚀失效的研究方向也由环境土壤对金属的腐蚀转入环境土壤对外防腐层非金属层的腐蚀及如何更好地发挥电化学保护作用方向上来 ,其中特别注重新型外防腐保护层技术的研究开发及复合保护技术的研究开发。因此 ,本文将着重讨论非金属外防腐层的相关腐蚀与防腐蚀问题。2 天然气长…     

长输管道防腐层技术现状和发展趋势

高性能防腐层是保障管道系统可靠性的重要技术手段。随着在恶劣环境敷设长输管道,对防腐层材料综合性能和施工技术提出更高要求。根据3LPE和FBE防腐层应用情况和技术问题,阐述了国内外新型防腐层及补口施工技术研究现状,并对管道防腐层技术发展趋势进行展望,对于提高我国管道建设施工水平和系统可靠性具有借鉴意义。     

输油生产管道中的防腐措施

埋在地下的输油生产管道很容易受到腐蚀。笔者针对输油生产管道中的防腐措施进行了探究,通过注重加强对输油生产管道的巡检、应用阴极防腐保护技术来展望防腐技术的发展。     

浅析原油管道防腐技术

在研究埋地原油集输管道防腐技术时,应先考虑管道的腐蚀环境,探究管道防腐技术的适用性。本文以埋地原油集输管道防腐技术及其适用性为主题,研究了具体的技术内容。     

用直流电位梯度法测量埋地管道防护层缺陷位置的模拟试验

介绍了埋地管道防护层缺陷电位梯度检测技术。用盐溶液、蒸馏水和自来水的混合液模拟土壤介质,通过改变管道防护层缺陷大小,改变环境电阻率和保护电流,试验证明了电位梯度检测技术能够比较准确地检测出管道防腐层缺陷的位置,并得到了管道埋深和地表电位梯度的关系。     

油田地面工程管道防腐施工技术应用分析

随着我国现代化社会发展不断深入,石油化工燃料作为基础能源的一种,社会需求上涨较为明显,也为油田地面工程的建设提出更高了的要求。石油的输送主要依靠管道系统完成,但由于管道受防腐技术、外界环境以及使用年限等因素的影响,油田管道腐蚀泄露问题时有发生。本文结合施工实际,详细分析了油田管道外防腐施工、强制电流阴极保护系统施工等技术要点的应用,通过本文的阐述,希望对今后油田地面工程的管道防腐施工起到指导和借鉴作用。     

在役埋地长输天然气管道补伤修复技术研究

为提高在役埋地管道补伤修复的质量,确保管道安全平稳运行,本文分析补伤修复的施工难点,结合补伤修复选材的基本原则,对国内外的补伤防腐材料进行了讨论得出:选择冷缠带或粘弹体弹体胶带+外保护带对在役管道进行补伤修复,两种防腐技术不仅能满足管道防腐的基本要求,同时防腐性能较好,施工方便,能够较好的对埋地管道3PE破损点补伤修复。     

剥离PE防腐层破损点下钢质管线的阴极保护

基于长输管线三层聚乙烯(3PE)防腐层失粘剥离现场开挖调查的情况,构建剥离防腐层下管道表面微区环境腐蚀模拟研究实验装置,研究华南酸性土壤环境条件剥离防腐层下管体表面的阴极保护和微区环境特征,采用微电极技术监测剥离区管线钢表面的局部电位和环境p H值的变化。结果表明,剥离区管线的有效保护距离随阴极保护电位负移而增加;在高电阻率酸性土壤环境中,剥离防腐层下的阴极保护仅限于破损点附近,剥离区深处管体处于自腐蚀状态;剥离防腐层下阴极保护有效性及其屏蔽程度可由剥离防腐层下微区溶液p H值判定。     

喷涂聚脲涂层在管道上的应用

喷涂聚脲涂层是近10年新发展的一种防腐技术，2002年国外已成立了聚脲研发协会(PDA)，全面负责聚脲技术在各领域的应用。聚脲涂层集多种优异性能于一身，例如低温快速固化，对湿度不敏感，有优良的防腐和力学性能，对环境无污染，是对传统防腐、防水涂料的一项创新。本文论述了喷涂聚脲涂层在管道上应用的前景。     

埋地管道防腐层维修材料的选择

防腐层是埋地管道最重要的防护措施,可以有效地保护管道不受腐蚀,但随着运行时间的推移,管道防腐层已不断老化,防腐性能下降,对防腐层的更换维修已成为管道日常管理工作的重要内容。为了选择适合管道防腐层维修的防腐材料,我们对6种材料进行了现场对比试验,为材料的选择提供了依据。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.