一起电站锅炉严重腐蚀的原因分析及处理措施

某电站锅炉水冷壁发生爆管泄漏,通过水冷壁厚度、材质、金相分析及腐蚀产物成分分析,确定水冷壁失效的直接原因是锅炉水质不合格导致的严重腐蚀。根据事故原因提出了具体的应对措施。     

火电厂水冷壁管失效分析

通过宏观形貌检查、金相检验、化学成分分析、力学性能测定及能谱分析等手段,分析了某火电厂锅炉水冷壁管爆管原因。结果表明,水冷壁管向火侧内壁严重氧化和高温氢腐蚀是锅炉水冷壁管破裂及爆管在主要原因,针对水冷壁管爆破提出了改进措施。     

水冷壁氢脆问题探讨——茂名热电厂3#炉水冷壁氢脆爆管的原因浅析

本文运用热力设备中锅炉水冷壁的介壳式腐蚀机理，寻找3^#锅炉水冷壁氢脆爆管的原因，并提出防止氢脆的措施。     

某电厂锅炉水冷壁管爆裂原因分析

通过宏观分析、金相、SEM、能谱、XRD等手段分析了水冷壁管失效原因。结果表明,水冷壁管发生了酸性氢腐蚀,锅炉长期水质较差,且运行过程中pH值偏低是其腐蚀减薄的主要原因,而腐蚀产物中沉积的Cu及其氧化物,形成垢下腐蚀环境,加速了水冷壁管的腐蚀,最终在锅炉介质应力作用下发生脆性爆管。     

电厂水冷壁管爆管失效的原因

某电厂锅炉水冷壁管发生了爆管。通过失效管道宏观形貌和显微组织观察、管材化学成分和力学性能检测、腐蚀产物成分分析等对该水冷壁管爆管的原因进行了分析。结果表明：爆管位置有明显腐蚀沟槽，局部位置发生了Na元素浓缩，腐蚀产物主要为铁的氧化物(Fe₃O₄和Fe₂O₃)、水垢和一定量的NaFeO₂;断口无明显塑性变形，宏观形貌表现为脆断特征，微观形貌表现为沿晶断裂特征；爆管位置组织为铁素体+珠光体，组织中有大量沿晶裂纹；锅炉运行期间，锅炉水pH出现过一段时间较高(10.0～10.2)的情况。综合以上分析，确定水冷壁管失效原因为碱腐蚀引起的应力腐蚀开裂。     

锅炉水冷壁腐蚀及爆裂的原因分析和防止对策

锅炉水冷壁不仅在水气侧发生腐蚀,而且在烟气侧也能发生腐蚀,由于腐蚀引起的水冷壁爆裂具有突发性,一旦发生腐蚀,爆裂后果较为严重。高参数锅炉水冷壁腐蚀爆裂通常发生在燃烧器中心线位置标高附近,涉及范围较大,严重危及机组的安全运行,锅炉水冷壁腐蚀爆裂的部位通常在热负荷最     

浅析锅炉水冷壁管外部均匀腐蚀原因

对一起锅炉水冷壁管爆管事故进行了分析，探讨了锅炉炉膛受压元件的外部均匀腐蚀的原因并提出了预防措施.      

锅炉管子难焊部位的几种焊接技巧

我厂是１９６０年投产的国产火力发电厂,由于机组运行时间长,老化严重,有时会在锅炉管子难焊部位发生爆管,给焊接检修带来麻烦,也因此影响了生产。为了提高检修工作效率,下面介绍几种解决这类管子爆管的焊接方法,以供参考。１　开天窗焊接我厂一台１００ＭＷ的锅炉水冷壁管位于前墙顶棚部位发生爆管,顶棚离炉底有４０ｍ高,如果按通常搭架到位再检修的话,需用四天时间。而用开天窗方法焊接仅需一天时间。首先把靠近爆管部位的前墙水冷壁管割断６根,每根长约８００ｍｍ,形成一个缺口。在缺口处搭架,然后补焊顶棚水冷壁管。接着焊…     

某生物电站锅炉水冷壁腐蚀原因分析

针对生物电站锅炉水冷壁腐蚀爆管问题,通过对爆管进行宏观分析、化学试验、金相组织分析以及垢样的电镜分析,认为碱金属氯化物(KCl)是产生高温腐蚀的主要原因,烟气冲刷引起的外壁高温为加速腐蚀提供了条件.     

水冷壁让位弯管爆管失效分析

火力发电厂锅炉后墙水冷壁折焰角下部向火侧密封盒内让位管弯头发生爆管,导致机组停运。通过宏观检查、金相组织观察、内壁氧化皮检查,对爆管原因进行分析,结果发现:爆管是由于原焊缝中的气孔在运行过程中发生垢下腐蚀、酸性腐蚀;经过长时间的垢下腐蚀和酸腐蚀,焊缝气孔逐渐向外扩展直至穿透,发生泄漏,造成介质流量减少,导致上部管段产生短时过热,最终发生泄漏爆管。建议对爆口附近区域管系进行相关检查,根据检查结果确定换管区域,在结构相似、温度较高部位增加温度测点,运行中加强监控。     

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).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。