Nitridation in NH3‐H2O‐mixtures

Exposures were conducted of iron, nickel, ferritic 1‐18%Cr steels, austenitic 18%Cr‐9%Ni‐ and 20%Cr‐31%Ni‐steels and a 16%Cr‐Ni‐base alloy at 500°C in He‐30%H₂O and 70%H₂O‐30%NH₃, to compare the corrosion behaviour of these materials in water vapor as in conventional power plants with their behaviour in a NH₃‐H₂O mixture, i.e. under conditions of the “Kalina‐cycle”. After 50 h in He‐H₂O generally a dense oxide scale had grown on iron and on the steels, whereas the scale grown in NH₃‐H₂O was porous, due to initial formation of the γ′‐ and ε‐nitrides, which are converted to Fe₃O₄ later. The porous scale allows internal nitridation of the Cr‐steels, nitrogen is transferred into the metal phase and reacts to finely dispersed CrN‐precipitates. This process causes stresses in the material and formation of cracks. The higher the Cr‐content of the material, the worse is the damage of the materials surface. Least corrosion damage occurs for iron and the 1%CrMo‐steel, however, the inward penetration of nitridation is greatest, and after 5 years on the low Cr‐steel a layer of about 15 mm would be embrittled by internal nitridation, formation of γ′ and ε‐nitride layers and external oxidation. Nickel is strongly damaged by intermediate formation of instable Ni₃N, which causes internal stresses and cracking, but also pore formation by its decomposition. The surface region of the 15%Cr‐Ni‐base alloy is also destroyed by internal nitridation and extrusion of Ni‐particles, while for this material the inward penetration of nitridation is relatively slow due to the low solubility and diffusivity of N in Ni and Ni‐alloys.     

锅炉压力容器焊接质量控制

对影响锅炉压力容器焊接质量的6个环节,即焊接工艺评定与焊接工艺,焊接材料,施焊过程,焊工培训,焊接检验,焊缝返修从理论和实践上进行充分论述,提出了保证焊接质量应采取的工艺措施,对提高锅炉压力容器焊接质量具有指导作用。     

Performance of cold sprayed Ni‐20Cr and Ni‐50Cr coatings on SA 516 steel in actual industrial environment of a coal fired boiler

Power plants are one of the major industries suffering from severe erosion–corrosion (E‐C) problems resulting in substantial losses. One way of tackling this problem is by the use of thermal spray coatings. In the current investigation a new emerging technique i.e. cold spray coating process was used to deposit Ni‐20Cr and Ni‐50Cr powder on SA 516 (grade 70) boiler steel. The bare as well as the coated steels were subjected to cyclic experimental studies, in the superheater zone of a coal fired boiler. Weight change, thickness loss, XRD, FE‐SEM/EDS and X‐ray mapping techniques were used to analyse the eroded‐corroded specimens. The uncoated steel showed weight gain after exposure in the actual boiler environment, whereas, for the coated steels there was initial weight loss followed by negligible weight change. Based upon thickness loss data the cold‐sprayed Ni‐50Cr coating was found to provide better E‐C resistance than the Ni‐20Cr coating.     

焊接技术在电站锅炉集箱制造中的应用

根据电站锅炉集箱常用的材料和结构特点,阐述焊接技术在电站锅炉集箱制造中的应用现状。结合集箱不同焊缝的焊接生产过程,分析GTAW、SMAW、SAW、FCAW等方法在集箱焊接中应用的特点,并指出焊接技术在电站锅炉集箱制造中的发展方向。     

HG-1900/25.4-YM4型锅炉安装焊接方案

焊接是锅炉安装中的一道重要工序,合理的焊接施工方案能够降低焊接难度,减轻工人劳动强度,提高焊接质量.详细分析了HG-1900/25.4-YM4型锅炉安装施工中省煤器、水冷壁、再热器、过热器、P91大径管焊接施工方案,指出安装中需注意的问题,为同类型锅炉的焊接施工组织及实施提供了借鉴.     

Field exposure of FeCrAl model alloys in a waste‐fired boiler at 600°C: The influence of Cr and Si on the corrosion behaviour

The aim of this study was to examine the performance of FeCrAl model alloys in a waste‐fired boiler and investigate the influence of chromium and silicon content on the corrosion behaviour. The investigation was executed by utilising an air‐cooled probe, giving a material temperature of 600°C throughout a 672 hr exposure. The material loss measurements were performed by utilizing an ultrasonic thickness gauge in combination with scanning electron microscopy analysis. It was found that increasing the chromium content significantly reduced the overall material loss of the FeCrAl model alloys but further accelerated the corrosion attack on the windward side. Simultaneously, the increased chromium content caused embrittlement of the material. Minor additions of silicon drastically reduced the material loss of the FeCrAl model alloys, whereas the sample ring with no silicon present was completely deteriorated. The trends observed in this field study correlated well with what has been observed in previous laboratory studies. A state‐of‐the‐art alloy in the present environment, Inconel 625, was simultaneously exposed and showed similar performance to the silicon‐containing FeCrAl model alloys with ≥10 wt% Cr.     

CO2/MAG焊接技术在锅炉压力容器生产中的应用

讲述了CO2/MAG焊接方法在锅炉压力窗口生产中的应用，推荐的典型焊接工艺，可提高焊接接头冲击韧性；并列举了MAG焊、药芯焊丝CO2气保焊在受压元件中的焊接应用。     

锅炉焊接机器人离线编程系统

主要研究开发了适于锅炉焊接的机器人离线编程系统。针对锅炉件的特点，建立了该空间焊缝的特征坐标系，并设计特征提取算法，进而规划出焊枪的运动路径与理想姿态，建立了典型的锅炉工件、日本安川SK6机器人等运动仿真环境。根据日本安川机器人程序的语言格式，采用该软件自动生成了机器人程序．对锅炉焊接过程进行了离线仿真试验，验证该系统是切实可行的。     

锅炉集箱短管接头机器人焊接系统

集箱作为电站锅炉系统的重要组成部分,涉及的材料范围广、尺寸规格多,长期以来多采用人工或半自动专机进行焊接,生产方式落后、效率低下且质量难以保证。为提高锅炉集箱短管接头焊接自动化程度和焊接质量,研制了以焊接机器人和搬运机器人为核心,辅以现场管理系统等的集箱短管接头机器人智能焊接系统。经过试验,该系统自动化程度高、控制精度高、焊缝成形良好,实用价值较高。     

甲醇装置用废热锅炉管板的修复

甲醇装置用废热锅炉管板在使用过程中局部出现了裂纹,为保证设备的正常运行,需进行修复.由于换热管与管板材质均为低合金耐热钢,含有较多的Cr-Mo,空淬倾向大,焊接时易出现冷裂纹,同时为了消除焊接应力和焊缝金属组织,焊后必须进行热处理.结合Cr-Mo耐热钢的焊接特点、现场施工条件和缺陷情况,制定了管板修复方案,采用手工钨极...     

电站锅炉智能化焊接现状和发展趋势

焊接技术在电站锅炉制造中起着至关重要的作用,随着电站锅炉向大容量、高参数方向发展,其材料等级越来越高、结构越来越复杂,传统的焊接工艺和装备将不能完全适应电站锅炉制造需求。阐述电站锅炉焊接技术及装备现状,指出现有电站锅炉焊接设备机械化高、但自动化和智能化低的现状,结合电站锅炉发展趋势及国家智能制造规划,提出了电站锅炉焊接工艺和装备的智能化需求和发展方向。     

Optimisation of in‐service performance of boiler steels by modelling high‐temperature corrosion

The main objective of the EU OPTICORR project is the optimisation of in‐service performance of boiler steels by modelling high‐temperature corrosion, the development of a life‐cycle approach (LCA) for the materials in energy production, particularly for the steels used in waste incinerators and co‐fired boiler plants. The expected benefits of this approach for safe and cost effective energy production are: ‐ control and optimisation of in‐service performance of boiler materials, ‐ understanding of high‐temperature corrosion and oxidation mechanisms under service conditions, ‐ improvement of reliability to prevent the failure of components and plant accidents and ‐ expanding the limits of boiler plant materials by corrosion simulations for flexible plant operation conditions (steel, fuel, temperature etc.). The technical aim of the EU OPTICORR project is the development of modelling tools for high‐temperature oxidation and corrosion specifically in boiler conditions with HCl‐ and SO₂‐containing combustion gases and Cl‐containing salts. The work necessitates thermodynamic data collection and processing. For development and modelling, knowledge about the corrosion mechanisms and exact data are needed. The kinetics of high‐temperature oxidation and corrosion are determined from laboratory thermo‐gravimetric tests (TG) and multi‐sample exposure tests. The materials studied are typical boiler tubes and fin‐steels: ferritic alloys, the austenitic steel T347 and the Ni‐based alloy Inconel 625. The exposure gases are dry air, air with 15 vol‐% H₂O, and with 2000 ppm HCl and 200 ppm SO₂. The salt deposits used are based on KCl‐ZnCl₂ and Ca, Na, K, Pb, Zn‐sulfates. The test temperatures for exposures with deposits are 320 and 420°C and, for gas exposures, 500 to 600°C. At present the tools being developed are ChemSheet based programmes with a kinetic module and easy‐to‐use interface and a more sophisticated numerical finite‐difference‐based diffusion calculation programme, InCorr, developed for prediction of inward corrosion and internal corrosion. The development of modelling tools for oxidation and high‐temperature corrosion was started with thermodynamic data collection for relevant systems and thermodynamic mappings. Further, there are needs to develop the simulation model and tool for salt‐induced hot corrosion based on the ChemSheet approach. Also, the work on modelling and simulating with the InCorr kinetic modelling tool will be continued to demonstrate the use of the tool for various steels and alloys in defined combustion environments.     

锅炉膜式壁管屏销钉自动焊工艺及系统开发

火电锅炉膜式壁管屏制造中存在大量的销钉焊接,为解决目前手工销钉焊存在的工人劳动强度大、焊接质量不稳定的缺点,有必要开发一种适用于锅炉生产的销钉焊自动焊接系统。通过分析锅炉自动销钉焊实施所面临的技术难点,从选用焊接设备、焊接工艺、销钉性能及送钉系统等方面进行试验研究。结果表明,采用短周期电弧螺柱焊接电源并配合特殊要求的销钉可实现无瓷环销钉的焊接,采用振动盘送钉方式可解决自动送钉的问题,不带瓷环焊接工艺的开发与振动盘送钉系统的研发为锅炉销钉的自动化焊接的实施奠定基础。     

BHW35锅炉汽包纵缝埋弧自动焊接工艺

分析了BHW35锅炉用钢的焊接性能,采用埋弧自动焊接设备进行了BHW35超高压锅炉汽包纵缝的焊接工艺试验,使用金相显微镜观测了母材和焊接接头的微观组织。结果表明,母材和热影响区组织为铁素体与贝氏体,熔合线处微观组织为贝氏体,焊缝微观组织为少量铁素体与贝氏体。进行了常温、350℃高温的焊接接头拉伸试验,弯曲角度为100°的弯曲试验,近缝区、焊缝区冲击试验。试验结果表明,试验结果符合BHW35超高压锅炉汽包纵缝焊接工艺要求,制订的焊接工艺可行。     

SA-335P122在超超临界锅炉中的应用

通过斜Y坡口裂纹试验和热模拟试验,确定了SA-335P122的预热温度和热处理规范,并通过对SA-335P122焊接性能分析和焊接材料的合理选用,成功地完成了玉环1000MW超超临界锅炉主蒸汽管道φ559mm×102mmSA-335P122的焊接。     

Corrosion of HR3C heat exchanger alloy in a biomass fired PF utility boiler

Detailed microscopic examinations have been conducted on two, temperature‐regulated probes (commercial HR3C heat exchanger alloy) after being exposed to biomass flue gas inside a PF boiler for 3770 h at 600°C and 650°C respectively. Corrosion of the tube proceeds via scale formation and internal element depletion. Three characteristic types of internal corrosion have been identified depending on their position relative to the flue gas passage and deposit/flue gas chemistry. Severe, mainly internal corrosion occurs at down‐stream locations where higher potassium chloride content exists within the deposit. Corrosion mechanisms corresponding to each type of internal corrosion have been proposed based on further laboratory tests and thermodynamic analysis. The increased temperature (650°C) causes slightly higher material wastage for the alloy.     

Laboratory‐simulated fuel‐ash corrosion of superheater tubes in coal‐fired ultra‐supercritical‐boilers

The corrosion behaviour of a number of Ni‐base alloys of different composition together with a highly‐alloyed austenitic stainless steel has been investigated with and without coating of the samples with alkali‐containing synthetic coal ash. The effects of various parameters have been studied, namely the Cr content (from 20 to 28 mass % Cr), the test temperature (700 and 775°C), the SO₂ content in the gas (1 vol% and 0.25 vol % SO₂) and the alkali sulphate content of the ash (10 and 30 mass%). The results can be explained on the basis of the differences in corrosion mechanisms resulting primarily from the composition of the alloys tested.