High performance alloys for solving severe corrosion problems in flue gas desulfurization systems

Nickel-base alloys have been used as cost-effective measures in a variety of severely corrosive situations in pollution control units for coal-fired power plants. Cost-effectiveness and practical answers to corrosion problems are illustrated (specifically the “wallpaper concept”/metallic lining technique). Numerous cases of successful use of HASTELLOY® alloys in Flue Gas Desulfurization (FGD) system are listed. New developments in nickel-base alloys and their use in FGD components are discussed. In the Ni-Cr-Mo-W alloy family, C-22? alloy has the best resistance to localized corrosion in halide environments (chlorides/fluorides-containing solutions). The H-9M? alloy is the latest development in the Ni-Cr-Mo-Fe alloy family. This alloy has shown superior performance in its resistance to localized corrosion, compared to alloy 625. H-9M alloy has been tested in several FGD systems and placed in field service. This iron-containing alloy is an attractive candidate due to its moderate cost.     

Corrosion in flue gas desulfurization plants and other low temperature equipment

A literature study of corrosion problems in flue gas desulfurization (FGD) plants and other low-temperature equipment has been made. The study in question has been limited to coal- and waste-fired plants. The results of the study shall contribute to selection of better materials and an optimization of the flue gas processing in such a way that the corrosion risk will be diminished leading to less costs of operation and maintenance. Before the selection of materials for FGD plants experiences from similar plants, pilot plant data, laboratory results and general recommendations for material selection must be carefully studied. Material recommendations from manufacturers are of great value, especially when selecting organic or inorganic coatings alternatively linings. The choice of an alloy is strongly dependent on the process chemistry, above all the pH and the chloride concentration. In several cases high-alloyed steels, nickel base or titanium alloys are recommended, e.g. nickel base alloys or titanium can be installed either as solid plates, clad plates or attached liners. Properly selected protective linings or coatings of non-metallics applied in a qualified manner and maintained well will, however, perform cost-effectively. Different ways to minimize the corrosiveness of the process environment have also been discussed, e.g. the use of inhibitors but considerable interest has also been devoted to corrosion monitoring.     

Effect of antimony on the corrosion behavior of low-alloy steel for flue gas desulfurization system

The alloying effect of Sb in a new low-alloy steel for the purpose of FGD materials was investigated by potentiodynamic polarization, linear polarization resistance measurement, electrochemical impedance spectroscopy (EIS) and weight loss measurements in an aggressive solution of 16.9 vol.% H₂SO₄ + 0.35 vol.% HCl (modified green death solution) at 60 °C, pH −0.3. All measurements confirmed the marked improvement in the corrosion behavior of the low-alloy steel via the addition of a small amount of Sb, particularly for the 0.10Sb steel. Pitting corrosion was detected by scanning electron microscopy (SEM) on the surface of blank steel and 0.05Sb steel, but not 0.10Sb steel, after weight loss measurements. X-ray photoelectron spectroscopy (XPS) analysis of the corroded surfaces after EIS and linear polarization measurements showed that the decrease in corrosion rates was due to the formation of a protective Sb₂O₅ oxide film on the surface of the Sb-containing steels. Moreover, the addition of 0.10% Sb stimulated the development of high corrosion inhibiting, Cu-containing compounds which further inhibited the anodic and cathodic reactions.     

Effect of tungsten on the corrosion behavior of sulfuric acid-resistant steels for flue gas desulfurization system

Flue gas desulfurization systems (FGDs) are operated in severely corrosive environments that cause sulfuric acid dew-point corrosion. The corrosion behavior of low-alloy steels was tested using electrochemical techniques (electrochemical impedance spectroscopy, potentiodynamic tests, potentiostatic tests), and the corrosion products were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical results showed that alloying W with small amounts of Sb, Cu, and Co improves the corrosion resistance of steels. The results of surface analyses showed that the surface of the steels alloyed with W consisted of W oxides and higher amounts of Sb and Cu oxides. This suggests that the addition of W promotes the formation of a protective WO₃ film, in addition to Sb₂O₅ and CuO films on the surface.     

Tensile yield load solutions for centre cracked bilayer (clad) plates with and without repair welds

Abstract

Bilayer metallic structural components in the form of clad plates are often used owing to their superior environmental and mechanical properties. During the service life of these components, cracks or cracklike defects may be developed in the clad layer and may grow into the substrate. To repair the damaged regions, local repair welding techniques are often used. The presence of this repair welded part may affect the deformation behaviour, and hence yield load level, of the structure. Therefore, in the present paper, new analytical tensile yield load solutions for centre cracked clad steel plates (austenitic cladding on a ferritic substrate) with a repair weld have been developed and these provide good agreement with experimental results. Additionally, a previously reported tensile yield load expression for a centre cracked clad plate (without a repair weld) has also been verified using the experimental results.     

烟气脱硫(FGD)装置耐腐蚀合金的选择

石灰石-石膏湿法烟气脱硫装置是目前国内外火电厂应用最成熟的环保工艺。其中脱硫洗涤塔是关键的设备。该设备腐蚀环境苛刻,如何选择合适的材料是洗涤塔的关键问题。本文介绍了洗涤塔的腐蚀机理及选择材料的方法。     

国产化转炉一次烟气干法净化回收系统研究与应用

介绍了转炉一次烟气干法净化回收系统应用背景,重点介绍了由中国重型机械研究院对该系统的研究开发成果及成功应用于冶金、有色等行业的相关烟气净化回收处理系统中的情况.根据应用于不同工况,其系统工艺及系统控制更应适应各工况特点,应不断完善其系统工艺及系统控制功能,使国产化干法净化回收系统运行更加稳定、可靠.     

转炉煤气干法净化回收系统中的蒸发冷却器

转炉高温烟气采用蒸发冷却器作为烟气冷却设备,通过向其内喷入按一定比例的气水混合物颗粒,利用水的汽化潜热将烟气温度迅速降低,同时也降低了烟气的含尘浓度和粉尘比电阻,且没有污水等二次污染问题.本文主要介绍了转炉干法除尘系统中蒸发冷却器的设计和计算.     

三峡工程泄洪深孔不锈复合钢板的焊接工艺

三峡水利枢纽工程泄洪坝段深孔一、二期金属结构埋件过流面均采用不 锈复合钢板制造，其基层低合金钢可以满足结构对强度和刚度的要求，,而复层不锈钢则可满足结构对耐磨耐腐蚀性能的要求。不锈复合钢板在水工钢结构制造安装中属首次应用。通过大量的工艺评定试验，并结合工程施工应用实践，详细地介绍了不锈复合钢板的焊接工艺。     

转炉煤气干法除尘技术在国内钢厂的应用

转炉干法除尘技术已在我国钢厂推广应用,该技术主要由蒸发冷却器、静电除尘器和煤气冷却器等组成。生产实践表明,该系统运行稳定,净化后的烟气含尘量小于10mg/m3,且运行费用低。     

Analysis of alloying systems of clad stamping tools for cold deformation of metal (review)

Two alloying systems of stamping tools (with intermetallic and carbide hardening) are analysed. Analysis shows the high characteristics of the metal with different alloying systems. The heat resistance of the 100Kh4M5F2(Zr) alloy is not inferior to the R18 high-speed tool steel, and the hardness equals 58–62 HRC as a result of carbide hardening. The relative wear resistance of the 8Kh4GSV2M5F2T alloy was (ε = 2.65), impact toughness (0.28 MJ/m²) and hardness (55 HRC). The highest wear resistance was recorded for the K15M15N5Kh3B2 alloy with the following properties after heat treatment: impact toughness (0.1 MJ/m²) and hardness (39 HRC). The wear resistance is 2–2.5 times higher than that of the R18 high-speed tool steel and 6–6.5 times higher than that of Cr12 and Cr12Mo steels.     

改型403钢热加工工艺的优化

利用Gleeble-3180热模拟机对403(改型)钢进行了热压缩实验,绘出了其真应力—真应变曲线,并研究了在不同变形温度和应变速率条件下材料的动态再结晶规律.推荐一种热加工优化工艺:1050～1190℃区间内变形,同时应变速率应控制在0.1s-1以下,以确保高的能量耗散效率,金属稳态流动,尺寸均匀的再结晶晶粒以及高温压缩时少量的δ铁素体.     

Enhanced corrosion protection by powder coatings on hot rolled steel (HRS) for high-temperature applications

Hot rolled steel (HRS) has long been a major product to the motor industry for bodywork, as galvanised steel (zinc coatings), and it is widely used in building and as tinplate (including tin and chrome oxide coatings) for food, etc. can-making. Among more specialist uses its moderate production costs makes it suitable for the manufacturing process. In this study, newly developed corrosion protection enhanced silicone based powder coating was evaluated on hot rolled steel (HRS). The powder coating in this study was developed to withstand high temperatures up to 550°C without any degradation. In the study silicone resin was incorporated with fillers, corrosion inhibitors and fibres at various compositions to achieve maximum heat resistance and improved corrosion resistance. Protective behaviours of the differently formulated powder paints were investigated before and after heat exposure. The developed paint system was evaluated using various test methods such as heat resistance, salt spray, Electrochemical Impedance Spectroscopy (EIS), adhesion test and microstructure study using SEM. The evaluation of test results revealed that powder coating combining zinc dust particles and mineral fibres have better performance due to better corrosion and adhesion stability in the corrosive environment before and after heat exposure up to 550°C.     

Microalloyed Steels for Controlled Hot Plastic Deformation (A Brief Review)

Metal Science and Heat Treatment -     

Depolarization thermocurrents and frequency dependence of conductivity in standard and rolled (CH)x

The correspondence between thermocurrent of depolarization as a function of temperature and the frequency-dependent conductivity allows a dielectric response to be attained in the very low-frequency range. The small rolling effect only reflects the modification of compactness of the films. The nature and distribution of the traps are shown to be the same for both cis- and trans-(CH)_x. The main difference between the isomers is the much higher mobility in trans-(CH)_x, which is related to the ease with which the charge carrier can diffuse along the chain in this isomer. The temperature behaviour of the a.c. conductivity is found to be similarly activated for both isomers.     

我国400MPa热轧带肋钢筋应用现状和发展建议

介绍了近年来我国 40 0MPa热轧带肋钢筋推广应用的进展情况 ,典型应用实例 ,其有关标准的修订及与国外同类产品的性能比较。并对今后 40 0MPa热轧带肋钢筋的推广应用工作提出了建议。     

Synthesis and evaluation of Tris-hydroxymethyl-(2-hydroxybenzylidenamino)-methane as a corrosion inhibitor for cold rolled steel in hydrochloric acid

Tris-hydroxymethyl-(2-hydroxybenzylidenamino)-methane (THHM) was synthesized. The effect of THHM on the corrosion of cold rolled steel (CRS) in 0.1 M hydrochloric acid was then investigated by Tafel polarization curve and electrochemical impedance spectroscopy (EIS). Polarization curve results clearly reveal the fact that THHM is a good cathodic type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing THHM concentration but decreases with immersion time. Atomic force microscopy (AFM) reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Langmuir adsorption isotherm. THHM adsorbs on the sample probably by chemisorption.     

高强度硼钢22MnB5的热变形方程及其模拟应用

利用Gleeble-3500热模拟试验机,在温度为700℃～950℃、应变速率为0.01/s～0.4/s的条件下,对高强度硼钢22MnB5的热变形行为进行研究。结果表明,随着变形温度的升高,硼钢的延伸率升高,变形抗力降低;随着应变速率的提高,硼钢22MnB5的变形抗力和延伸率增大。根据高温拉伸实验得出的数据,构建硼钢22MnB5的稳态流变应力模型和热变形方程,并将试验结果和构建的本构方程输入ABAQUS软件进行U型件热弯曲成形的回弹模拟,数值模拟结果与实验结果吻合较好,验证了模型的可靠性和正确性,为成形所需的最大载荷及设备选择提供依据。     

亚洲最先进的(1+4)式热连轧生产线

简要介绍中国铝业公司西南舒;板带有限公司新建立的（1＋4）式热连轧生产线的概况,没备技术参数以及其特点。