自流进水冷却塔在高炉密闭循环水系统中的应用

介绍了自流进水冷却塔在重庆钢铁1#、2#高炉密闭循环水系统中的实际改造应用情况.巧妙地利用现场地势高差,蒸发空冷器喷淋回水经改造可自流进入新建的自流冷却塔,经冷却塔降温后,回水自流到喷淋水池,实现对喷淋水降温达到降低密闭循环水系统温度的目的.     

光辐射对丙烯酸聚氨酯涂层防腐保护性能的影响

以氙灯为光源,对丙烯酸聚氨酯涂层/碳钢体系进行人工加速老化实验,用傅里叶变换红外光谱仪(FTIR)、光学显微镜和光泽仪对老化的涂层进行分析表征,用盐雾实验测试涂层老化后的防腐性能,初步探讨了光辐射对涂层保护性能的影响.结果表明,不同老化周期的体系在盐雾实验后,表面涂层的保护状态均基本完好,但膜下金属腐蚀程度随老化时间的增加而加剧.其原因是:光辐射使涂层中C—N键断裂,且随老化时间的延长,涂层表面粗糙程度增加,光泽度下降;涂层化学结构及表面状态的变化加速了腐蚀介质在涂层中的渗透,从而导致膜下金属腐蚀加重.     

涂层界面失效过程的ESPI无损检测方法

基于激光电子散斑干涉技术(ESPI),对涂层失效过程的电子散斑干涉技术检测平台进行设计搭建,在不破坏涂层前提下,观察到浸泡失效过程中涂层的原位、实时和动态干涉条纹,并对其进行优化处理.将原位、实时观察到的条纹与零时刻条纹图像相减后进行计算机二值化处理,得到反映涂层失效信息的原位、实时及动态图像.针对环氧色漆/碳钢涂装体系,证实了电子散斑干涉技术分析的有效性,并根据其检测图像的变化,将环氧涂层的浸泡过程分为三阶段:初期没有斑点,涂层完好;中期出现模糊的斑点,涂层防护作用下降;后期出现清晰的黑色大斑点,涂层丧失防护能力.实现了涂层/金属界面失黏、膜下金属腐蚀微观发展过程原位、实时和动态的无损检测.     

有机涂层室内加速实验的对比

研究了丙烯酸聚氨酯清漆涂层在荧光紫外UVA辐照/凝露和氙灯辐照/雨淋两种加速实验程序下的物理、化学性能和防护屏障性与暴露时间的关系.结果表明:氙灯辐照/雨淋对涂层的膜厚损失、失光率的影响程度略大于同周期UVA加速的效果;而黄色指数及不同暴露周期的完整涂层的低频阻抗模值与暴露时间的关系则与FTIR反映的羰基指数的变化规律较为一致,显示UVA加速涂层老化的效果大于同周期氙灯加速效果.且在两种加速条件下,完整涂层的低频阻抗模值均与暴露时间呈指数规律衰减,表现出较好的时间函数关系;说明EIS的低频阻抗模值与UV光辐射产生的涂层性能的变化有一定的相关性,并很好地反映其防护屏障性,可作为有效的监测参量用于建立室内外老化实验的相关性,预测光老化涂层的防护寿命.     

Q345C-NHY3耐海水腐蚀钢的涂装腐蚀行为

以耐海水腐蚀钢Q345C-NHY3+厚浆型环氧防锈漆涂装体系为研究对象,通过漆膜理化性能检测,结合中性盐雾、紫外光老化等实验研究了Q345C-NHY3的涂装特性与涂装腐蚀行为.同时采用EIS,考察研究了涂装体系在模拟海水介质中的中长期浸泡行为.结果表明:Q345C-NHY3+厚浆型环氧防锈漆涂装体系具有良好的耐阴极剥离性能,施加阴极保护可进一步提高体系的整体耐腐蚀性能.在模拟海水的介质中浸泡104 d后,涂层体系EIS谱的低频端表现出容抗特征,这表明溶液与钢板基体发生了电化学反应,涂层体系开始失效.     

扫描Kelvin探针研究破损环氧涂层下碳钢的腐蚀行为

采用扫描Kelvin探针技术(SKP)对中性盐雾环境条件下破损环氧涂层的碳钢的腐蚀行为进行了研究.不同盐雾试验阶段的伏打电位变化规律的分析结果表明:环氧/碳钢涂层的缺陷为腐蚀介质提供了向碳钢基体传输的通道.破损处碳钢基体的电位比其邻近的膜下碳钢基体更负,成为阳极溶解发生区域.一定时间的盐雾试验后,破损处生成的未溶腐蚀产物可覆盖住裸露基体,使破损处向正的电位变化而成为阴极,而其附近的膜下碳钢基体电位变负而成为新的阳极区.同时,不断形成的新阴极和新阳极的电位差成为膜下腐蚀继续发展的驱动力.随着膜下腐蚀的进行,腐蚀介质和腐蚀产物在界面处大量聚集,破坏了环氧和碳钢基体的结合力,导致鼓泡和剥离现象的出现.     

人工加速老化对聚脲涂料防护性能的影响

针对聚脲涂料防腐涂层进行紫外加速老化实验,采用光泽度计、扫描电子显微镜(SEM)以及傅里叶变换红外光谱仪(FTIR)分析并结合电化学阻抗谱(EIS)图谱,研究涂层的老化行为.结果表明:涂层的老化分为前期、中期和后期三阶段,涂层表面在老化中期变色较大.涂层的表面、断面SEM及EIS测试显示涂层中的微气泡阻止了涂层的老化裂纹向基体发展,涂层仍保持较好的防护性能.     

循环水系统技术改造

对炼钢循环水系统的VD浊环冷却水、连铸浊环冷却水、连铸设备间接冷却水、冷媒水的四组冷却塔以及连铸浊环水系统进行了技术改造,提升了生产供水的可靠性,降低了设备停机率和维修费用,杜绝了水资源浪费.科学合理地使用设备,对水系统的各个环节定期诊断和效能评估并及时进行调整,提高循环水的复用率,根据季节变化调整冷却塔运行方式以减少因蒸发和漂移造成的水量损失,在满足了生产需要的同时取得了节能、减排和降耗的效果.     

氧化铝蒸发工艺末效乏汽的余热回收利用

某公司氧化铝生产工艺采用大气冷凝器吸收乏汽,乏汽的热量和凝结水均得不到充分利用,同时采用冷却塔降温需要消耗大量循环水,循环泵和冷却塔风机电耗高.为了回收乏汽余热,通过方案比较,选用汽冷型第一类吸收式溴化锂热泵,改造蒸发器循环水系统,直接回收蒸发工艺末效蒸发器的乏汽潜热,使其成为供暖热源.乏汽余热回收每年可产生效益约11...     

动态力学法研究热氧老化对含钆有机玻璃性能的影响

对含钆有机玻璃在180℃条件下进行热氧老化实验,老化时间分别为0.25,0.50,1.00,2.00,3.00,5.00,7.00 d,老化前后的试样采用动态热机械分析仪(DMTA)、悬臂梁冲击试验仪和电动塑料洛氏硬度计进行测试,研究其储能模量、损耗模量、玻璃化转变温度、冲击强度和洛氏硬度的变化规律,同时根据储能柔量的垂直位移因子确定临界失效时间来推算含钆有机玻璃在25℃时的使用寿命。研究结果表明,随着热氧老化时间的延长,含钆有机玻璃的储能模量、玻璃化转变温度和洛氏硬度随热氧老化延长而增大,损耗模量和冲击强度随热氧老化时间增加而减小;根据含钆有机玻璃储能柔量的垂直位移因子确定了临界失效时间为10.56 h;利用从动态力学性能得到的寿命方程计算得到含钆有机玻璃在25℃下的使用寿命约为26.55年。     

海水温度对深海用环氧涂层防护性能的影响

采用电化学阻抗谱(EIS)技术,研究了环氧重防腐涂层在不同温度海水中的腐蚀电化学行为.结果表明,随着海水温度的升高,涂层体系的涂层电容值的升高和涂层电阻值的降低均加快,说明海水温度的升高,加速了涂层防护性能的下降,加快了基体金属的腐蚀.浸泡初期,在不同温度的海水中,水在涂层中的扩散均符合Fick扩散第二定律,扩散活化能为49.7kJ·mol^-1.随着海水温度的升高,涂层中水的扩散系数增大,涂层吸水达到饱和的时间缩短,但饱和吸水量变化不大.     

老化方式对聚氨酯涂层钢板失效行为的影响

运用四种加速方法对聚氨酯有机涂层钢板进行老化,并通过涂层的表观性能和电化学特征对比研究了老化方式对涂层失效的影响.紫外老化对涂层光泽的影响最大,老化32 d失光度达85.7%.盐雾实验前期线性极化阻力R_p迅速下降,后期由于盐膜的生成使得R_p保持稳定;氙灯和盐雾混合老化的光泽度和R_p的变化规律都表现为实验前期与光老化相似,后期则与盐雾实验相类似.此外,拟合不同老化方式的电化学交流阻抗谱发现:混合老化前期主要受氙灯影响,与单一氙灯老化的等效电路一致,表现为两个时间常数;后期产生盐膜,出现三个时间常数.     

Corrosion of Steel Reinforcement in Carbon Fiber-Reinforced Polymer Wrapped Concrete Cylinders

The rehabilitation, repair, and strengthening of concrete structures has increased worldwide with a growing number of systems employing externally applied fiber-reinforced polymer (FRP) composites. However, the service life and effectiveness of FRP repair and strengthening techniques when applied to concrete in corrosive marine environments is still not well understood. This paper presents the results of an experimental study on the corrosion performance of embedded steel reinforcement in cylindrical reinforced concrete specimens with 13 different surface treatment options. Samples were subjected to an impressed current and a high salinity solution. Test variables included the type of epoxy, wrap fiber orientation, and the number of wrap layers. Samples were evaluated for corrosion activity by monitoring corrosion potentials and impressed current flow levels, and by examining reinforcement mass loss and concrete chloride content among samples. Test results indicated that FRP wrapped specimens had prolonged test life, decreased reinforcement mass loss, and reduced concrete chloride content. The performance of wrapped specimens was superior to that of either control samples or those coated only with epoxy. Epoxy type had a significant effect on the performance of samples regarding their resistance to corrosion. It was concluded that carbon FRP wraps were able to confine concrete, slowing deterioration from cracking and spalling and inhibiting the passage of salt water.     

空气压缩机冷却系统改造

针对天铁动力空气压缩机冷却系统出现的空压风温差高报警现象,分析出其产生原因是冷却系统循环水温度高和水质差。通过对冷却系统进行改造,消除了上述现象,延长了相关的设备的使用寿命,保障了冷却系统的正常运行。     

Effect of Thin Polymer Coatings on the Mechanical Properties of Steel Plates

The influence of powder coatings based on an epoxide polyester mixture on the mechanical properties of the plates made of rolled sheet steel is studied. The influence of 100-μm-thick coatings on the mechanical properties of specimens 0.7–1.5 mm thick is considered. The bending and tensile tests performed at room and elevated temperatures show that the thin coatings weakly affect the mechanical properties of the plates. In particular, the stiffness of the coated plates during tension and bending remains almost the same despite the fact that the elastic modulus of the coated plates is always slightly lower than Young’s modulus of steel because of an increased specimen thickness determined with allowance for the presence of a coating. The influence of the coatings is substantial in compressive stability tests. Under supercritical deformation conditions, the bearing capacity of the coated plates decreases substantially, and their critical stability load on the loss of stability falls by 20–30% (depending on the substrate thickness). This effect can be explained by the influence of the residual thermal stresses that appear in the specimens during coating deposition.     

一种高炉用水冷紧凑式垂直探尺的研发

针对高炉普通探尺在使用中存在的弊端,研发了一种新型紧凑式垂直探尺装置。该探尺装置首次采用水冷结构设计,布置紧凑,能有效避免因润滑脂过热炭化造成的轴承失效及密封元件受热传导和热辐射作用老化过快的弊端,同时也可提高电气元件长期在高温及多粉尘条件下的工作可靠性,减少高炉的休风次数,延长整机的使用寿命。     

High Temperature Erosion Performance of Nanostructured and Conventional TiAlN Coatings on AISI-304 Boiler Steel Substrate

According to modern design philosophy better overall performance can be obtained with the modification of the surface structure and their properties without damaging underlying bulk material or substrate. The surface engineering can be classified in two broad classes: surface modification and surface coating. In the present research TiAlN coating was deposited on AISI-304 grade boiler steel using three different techniques, out of which two were thin nano coatings deposited at different temperatures of 500 and 200 °C developed by Oerlikon Balzers rapid coating system machine under a reactive nitrogen atmosphere. One conventional coating of TiAlN was deposited by plasma spraying method. The coated samples were characterized relative to their coating thickness, microhardness, porosity and micro structure. The optical microscopy, the X-ray diffraction analysis and field emission scanning electron microscope (FESEM with EDAX attachment) analysis have been used to identify various phases formed after coating deposition on the surface of AISI-304 grade boiler steel. The erosion studies were conducted on uncoated as well as coated specimens in simulated coal fired boiler environment using an air jet erosion test rig at various impingement angles of 30°, 60° and 90°. The alumina particles of average size of 50 µm were used as erodent at a velocity of 35 m/s. The eroded samples were analysed with SEM/EDAX and optical profilometer. The main objective of this research work was to increase the life of boiler tubes by using nanostructured and conventional TiAlN coatings and at the same time to compare the performance of coatings with respect to bare AISI-304 grade boiler steel. The nanostructured TiAlN coatings has shown minimum erosion rate as compared to conventional TiAlN coating and uncoated AISI-304 grade boiler steel. Maximum erosion was observed at an angle of 30° as compared to 60° and 90° indicative ductile behaviour.     

Modeling Water and Sulfuric Acid Transport through Coated Cement Concrete

The behavior of coated cement concrete in water and sulfuric acid was investigated over a three-year period. Two epoxy-based coatings were selected and cylindrical concrete specimens were coated and used in this investigation. The concrete-to-coating mass transfer coefficient ratio varied from 8 to 10. The penetration of liquids through bulk coating materials and coated concrete with and without holidays (pinholes) was studied. The mass change of the specimens was measured at regular intervals and a total of 64 coated specimens were tested. Coated concrete specimens with and without holidays had different performance with long-term immersion in deionized (DI) water and 3% sulfuric acid. Mass transfer models were developed using film and bulk concepts and were used to predict the increase in mass in coated concrete in nonreactive DI water and reactive 3% sulfuric acid solutions. The mass transfer model parameters for various solution-coating combinations were obtained from experiment data. The parameters of the effect of holiday size on the liquid transport process were also identified based on the experiment results.     

Decomposition of the B2-type matrix

The microstructural stability of aluminide diffusion coatings, prepared by means of a two-stage pack-aluminization treatment on single-crystal nickel-base superalloy substrates, is considered in this article. Edge-on specimens of coated superalloy are studied using transmission electron microscopy (TEM). The effects of coating thickness and post-coating heat treatment (duration, temperature, and atmosphere) on coating microstructure are examined. The article discusses the partial transformation of the matrix of the coating, from a B2-type phase (nominally NiAl) to a L1₂ phase (nominally Ni₃(Al, Ti)), during exposure at temperatures of 850 °C and 950 °C in air and in vacuum for up to 138 hours. Three possible processes that can account for decom- position of the coating matrix are investigated, namely, interdiffusion between the coating and the substrate, oxidation of the coating surface, and aging of the coating. Of these processes, aging of the coating is shown to be the predominant factor in the coating transformation under the conditions considered.     

Study on preparation and properties of CeO2/epoxy resin composite coating on sintered NdFeB magnet

The CeO₂/epoxy resin composite coating was deposited on NdFeB substrate by cathode electrophoresis method for enhancing the anticorrosion and anti-wear performances. The morphologies and structures were characterized by a scanning electron microscope and an X-ray diffractometer. The micro hardness of the composite coating was evaluated by a microhardness tester. The corrosive behaviors of the coatings were studied by potentiodynamic polarization curve, electrochemical impedance spectroscopy and neutral salt spray tests. The concentration of CeO₂ nanoparticles (NPs) in the electrophoresis bath was optimized according to the coating structures and anticorrosion performances. The results show that CeO₂ NPs can enhance the microhardness of the composite coatings. Moreover, the nanoparticles disperse uniformly in the matrix when the concentration is lower than 30 g/L. The microhardness of CeO₂/epoxy resin (30 g/L) composite coating is about 63% higher than that of the blank epoxy resin coating. And the NSS time of the CeO₂/epoxy resin (30 g/L) composite coated sample can reach 1248 h. Meanwhile, the composite coatings possess no deteriorate influence on the magnetic properties of NdFeB substrates. The anticorrosion mechanisms of the composite coatings on the NdFeB substrate are deeply discussed.