Solders as high temperature engineering materials

Abstract

Although they operate at temperatures around ambient, it is argued that tin-based solders may be regarded as conventional high temperature engineering alloys, such as steels, titanium and nickel-base alloys, which normally experience much higher temperatures. This proposition is based upon a comparison at similar homologous temperatures, rather than their absolute values.

The demand for structural integrity of soldered joints in modern electronic devices is growing. Design challenges, quite similar to those in power generation and aerospace, require reliable life prediction under complex operating conditions. The paper compares monotonic and cyclic properties of solders with those of the more conventional high temperature alloys. Particular attention is focussed on the emerging lead-free solders which are being introduced for environmental reasons. It is concluded that solders are amongst the most vulnerable of high temperature alloys particularly with respect to their strain rate sensitivity and time dependent behaviour.     

高温下聚氨酯封堵材料的烟气分析及安全性评价

为了验证现场施工中聚氨酯封堵材料在爆破高温时的变化,在已有聚氨酯封堵材料研究的基础上,通过实验对其产生的有毒烟气种类和含量进行测量分析,并结合张承德高速公路隧道的TJ25标段施工对其进行安全性评价。首先采用热重-红外联用技术,对聚氨酯封堵材料在低于1 100℃温度条件下产生的烟气,进行了热解及定性分析,得出了不同温度烟气的种类和成分。然后将有毒烟气CO作为主要研究对象,使用烟箱及气相色谱实验测定其含量,对其在隧道施工过程造成的危险性进行了评价。结果表明,聚氨酯封堵材料热解产生的CO量符合有关规定,可以在工程中推广应用。     

高温下聚氨酯封堵材料的烟气分析及安全性评价

为了验证现场施工中聚氨酯封堵材料在爆破高温时的变化,在已有聚氨酯封堵材料研究的基础上,通过实验对其产生的有毒烟气种类和含量进行测量分析,并结合张承德高速公路隧道的TJ25标段施工对其进行安全性评价。首先采用热重-红外联用技术,对聚氨酯封堵材料在低于1 100℃温度条件下产生的烟气,进行了热解及定性分析,得出了不同温度烟气的种类和成分。然后将有毒烟气CO作为主要研究对象,使用烟箱及气相色谱实验测定其含量,对其在隧道施工过程造成的危险性进行了评价。结果表明,聚氨酯封堵材料热解产生的CO量符合有关规定,可以在工程中推广应用。     

Preparation of a modified flue gas desulphurization residue and its effect on pot sorghum growth and acidic soil amelioration

A modified flue gas desulphurization residue (MFGDR) was prepared and its effects on sorghum growth and acidic soil amelioration were evaluated in this paper. The MFGDR was prepared by calcining a mixture of dry/semi-dry flue gas desulphurization (FGD) residue from a coal-fired power plant, sorted potash feldspar and/or limestone powder. The available nutrients from the MFGDR were determined with 4.91 wt% K⁺, 1.15 wt% Mg²⁺, 22.4 wt% Ca²⁺, 7.01 wt% Si⁴⁺ and 2.07 wt% SO₄²⁻-S in 0.1 mol L⁻¹ citric acid solution. Its pH value was held at 9.60 displaying slightly alkaline. The results of sorghum pot growth in both red and crimson acidic soil for 30 days indicated that adding the MFGDR at a dosage of 2 g kg⁻¹ in total soil weight would increase the growth rate of biomass by 24.3-149% (wet weight basis) and 47.3-157% (dry weight), the stem length and thickness increase by 5.75-22.1% and 4.76-30.9% in contrast with CK treatment for two test cuttings, respectively. The effect on sorghum growth was attributed to the increase of available nutrients, the enhancement of soil pH value and the reduction of aluminum toxicity in acidic soil due to the addition of the MFGDR. The experimental results also suggested that the MFGDR could be effectively used to ameliorate the acidic soil which is widely distributed throughout the southern China.     

The behaviour of high temperature filter materials in hot gasifier and combustor gas atmospheres

Ceramic filt ers are promising devices for cleaning the high temperature gases from advanced coal-fired power generation processes. The stability of a range of candidate ceramic materials has been determined in gases produced from fluidized bed combustion and gasification processes. The materials have included ceramics based on alumina, alumino-silicates, zirconia and silicon carbide in the forms ofblankets, woven fabrics and rigid candles.Candle filters were found to produce the best compromise between initial strength and resistance to degradation. A number ofpossible degradation processes have been identified.     

Development and application of a methodology for the measurement of corrosion and erosion damage in laboratory,burner rig and plant environments

Abstract

Fuel gases derived from solid fuels such as coal, biomass and waste and their mixes have the potential to cause both erosion and corrosion damage to components in gas turbines and diesel engines. To allow the statistically valid assessment of materials performance in short term plant runs, burner rig tests and laboratory simulated environments a methodology has been developed to collect compatible quantitative data on materials degradation. Accurate measurement techniques based on pre-exposure contact metrology and post-exposure optical microscopy/image analysis have been developed. These take into account both the low level of damage required for practical systems and the localised nature of hot corrosion damage. The data produced have been used to derive and test quantitative models for the prediction of the performance of candidate materials in such power systems. For these models to be used with confidence, similar damage morphologies must be produced in both the real and simulated conditions, as well as similar damage rates.     

热-自组装单分子膜表面改性镁生物材料的腐蚀降解

将Mg和Mg-Ca合金进行热一自组装单分子膜表面改性,并将其试样浸泡在SBF中和植入动物体内进行比较试验,用LKI198B测试腐蚀电流密度,用原子吸收光谱测定溶液中的镁离子浓度,测量试样的质量和溶液pH值的变化,用SEM、XRD,FTIR、EDS等分析其表面形貌、物相组成和成分变化,研究了材料的腐蚀降解特性.结果表明,热自组装膜改善了镁基生物材料的腐蚀抗力和生物活性.纯Mg的腐蚀速率由0.11 mm/y下降到0.05 ram/y,Mg-Ca合金的腐蚀速率由0.38 mm/y下降到0.32 mm/y.植入动物12周后,直径的减小由0.97 mm下降到0.20 mm,界面新类骨质层厚度由2.56 mm增加到3.14 mm.     

不锈钢在烟气脱硫系统中的腐蚀行为

火电厂烟气脱硫系统的设备腐蚀问题比较严重,选材较为关键.为此,选用304不锈钢和2205双相不锈钢,考察了其在烟气脱硫模拟介质(死亡绿液)中不同温度和不同浸泡时间的腐蚀行为.结果表明:304不锈钢在死亡绿液中随温度变化腐蚀性很敏感,易发生点蚀,不宜用作烟气脱硫装置及其零部件;2205双相不锈钢在烟气脱硫模拟介质中不同温度和时间范围内都有良好的耐蚀性,可用作烟气脱硫装置及其零部件的材料.     

The influence of flue gas recirculation on oxy-oil combustion in an existing furnace

Oxy-fuel combustion has received increasing attention as one of the major solutions for CO₂ capture. This study aimed to obtain a better understanding on the oxy-oil firing process and to gain experience handling flue gas recirculation. A 300 kW_th multi-fuel combustion test furnace at National Cheng-Kung University in Tainan, Taiwan was chosen as the experimental facility. This experimental study had successfully converted a conventional air-fired furnace to operate on oxy-fuel firing with various operating conditions. Oxygen-enriched combustion and oxy-fuel combustion tests were conducted. The effects of oxygen enrichment, flue gas recirculation, fuel type, and thermal loading on the operational characteristics of the furnace such as temperature distribution, pressure variation, and emission characteristics were examined and discussed. Several concerns about a conventional air-fired furnace adapted for oxy-fuel combustion were scrutinized, including optimization of flue gas recirculation for better combustion efficiency, higher SO₂ concentration in the flue gas under oxy-fuel operation, and air leakage coming from negative pressure operation. These findings provided valuable data to improve the performance of oxy-fuel combustion and to allow better conceptual designs in future development.     

抗磨损抗腐蚀材料的新进展

本文综述抗磨损抗腐蚀新材料产品和制作工艺的某些新发展 ,重点论述制取抗磨损抗腐蚀层状陶瓷复合材料的等离子喷焊、喷涂法、氧乙炔喷焊法和自蔓延燃烧反应合成法 ,高能量密度束流熔涂制取金属基陶瓷复材的工艺和产品开发情况 ,简述了制取超硬面层金刚石与金属复合的高压反应合成法和等离子化学气相沉积法 ,也论述了电化学方法制取表层陶瓷的微弧氧化法和制取钢铁基钛铝表层抗蚀复材的熔盐电沉积研究进展。对真空浸渍法和热喷涂法制取塑料和金属复材的工艺和产品也作了简要论述。     

烟气余热换热器低温腐蚀分析及对策

根据句容发电厂1000MW超超临界燃煤机组烟气余热换热器的运行情况,研究了冷端受热面硫酸低温腐蚀现象,分析得出有效控制此现象的措施为严格控制烟气余热换热器进口水温和排烟温度等。     

聚苯胺及其掺杂材料的制备及气敏特性的研究

采用质子酸化学聚合法,以苯胺（An）为单体,过硫酸铵（APS）为氧化剂,在盐酸（HCl）溶液中,合成了聚苯胺（PANI）及In2O3、TiO2和SnO2掺杂的聚苯胺。分别通过X射线衍射仪（XRD）,红外光谱仪（FT-IR）,场发射扫描电镜（FE-SEM）对其结构和形貌进行了表征,制成了基于聚苯胺及其掺杂材料的氨气传感器。室温下,对1.0×10-5～1.50×10-4浓度范围的氨气进行了气敏测试,测试结果表明,基于聚苯胺及其掺杂材料的气敏元件对氨气响应灵敏度基本呈线性关系。掺杂In2O3的聚苯胺气敏元件对氨气的响应灵敏度最大,在1.50×10-4时响应灵敏度达到50;而掺杂TiO2的聚苯胺气敏元件对1.00×10-4氨气的响应时间最短,为60s。分析了聚苯胺及其掺杂材料的气敏机理,结果表明,金属氧化物的掺杂对聚苯胺材料的灵敏度、响应及恢复时间等气敏特性有很大的影响。     

响应曲面法研究碳钢在模拟烟气冷凝液中的腐蚀行为

电厂烟气冷凝液有较强腐蚀性,引起腐蚀的因素较多。采用响应曲面法研究了模拟烟气冷凝液中影响腐蚀的主要因素pH值、Cl-浓度与温度对碳钢腐蚀速率的影响,通过单因素极化曲线测定了碳钢的腐蚀电流密度。结果表明:随着溶液pH值的降低、Cl-浓度的增大和溶液温度的升高,腐蚀电流密度增大。在此基础上,运用响应曲面法中的BBD模型设计试验条件,测试并分析了碳钢在不同条件下的腐蚀速率,发现对碳钢腐蚀速率的影响程度从大到小依次为pH值﹥温度﹥Cl-浓度。     

基于区分度定量分析工程材料评价指标

为了建立科学的评价指标体系,降低评价过程的复杂性,合理分配各指标的权重,保证评价结果的客观性和科学性.在对工程材料评价指标进行标准化处理的基础上,提出评价指标的贡献和区分度概念,确定了指标定量筛选依据,即当区分度小于0.002时,该指标应该被剔除.以上述依据对6种低温存储罐材料(不锈钢)的8个评价指标进行筛选,根据筛选前后的两个指标体系,采用加权平均法,对6种候选的不锈钢材料进行综合评价.结果表明,由两组指标得出的评价结果完全一致,且后者由于删除了冗余指标,使得权重的分配更加合理和准确,因而显著提高了评价结果的差异程度,更好体现不同候选材料的优劣差异.说明基于区分度定量分析工程材料的评价指标合理、可行.     

The effect of hydrogen peroxide solution on SO2 removal in the semidry flue gas desulfurization process

The present study attempts to use hydrogen peroxide solution to humidify Ca(OH)₂ particles to enhance the absorption of SO₂ to achieve higher removal efficiency and to solve the valuable reuse of the reaction product in the semidry flue gas desulfurization (FGD) process. Experiments were carried out to examine the effect of various operating parameters including hydrogen peroxide solution concentration, Ca/S molar ratio and approach to adiabatic saturation temperature on SO₂ removal efficiency in a laboratory scale spray reactor. The product samples were analyzed to obtain semi-quantitative measures of mineralogical composition by X-ray diffraction (XRD) with reference intensity ratio (RIR) method and the morphology of the samples was examined by scanning electron microscope (SEM). Compared with spraying water to humidify Ca(OH)₂, SO₂ removal efficiency was improved significantly by spraying hydrogen peroxide solution of 1–3 wt.% to humidify Ca(OH)₂ because hydrogen peroxide solution enhanced the dissolution and absorption rate of SO₂. Moreover, XRD and SEM analyses show that the desulfurization products contain less amount of unreacted Ca(OH)₂ and more amount of stable calcium sulfate with increasing hydrogen peroxide solution concentration. Thus, the process mechanism of the enhanced absorption of SO₂ by spraying hydrogen peroxide solution to humidify Ca(OH)₂ was elucidated on the basis of the experimental results.     

高阻尼铝基复合材料在海水中的腐蚀行为

研究了高阻尼铝基复合材料在海水中的腐蚀行为,本实验所用高阻尼铝基复合材料是以6061铝合金为基体,加入SiC颗粒和石墨粉,用粉末冶金方法制备的。测定了高阻尼铝基复合材料在海水中的腐蚀速率度、电极电位和极化曲线,并通过与基体金属的对比来描述它的腐蚀特性。实验表明,在海水介质中,高阻尼铝基复合材料的耐蚀性能比6061铝合金差,孔蚀倾向大。在海水介质中使用高阻尼铝基复合材料必须加以保护。     

Mechanical degradation of foam-cored sandwich materials exposed to high moisture

Sandwich specimens composed of E-glass/polyester face sheets bonded to a PVC foam core were exposed to high moisture (95% RH) and immersed in sea-water for extended periods of time. Degradation of mechanical properties of the face sheets, foam core and face/core interface were progressively evaluated using flexural testing of the laminates, through-thickness tension of the foam core and interfacial sandwich DCB fracture testing. Testing reveals substantial flexural stiffness and strength reductions for the laminated composites, and only minor reduction in the tensile stiffness and strength of the foam. Degradation of the interfacial face/core fracture toughness is weak for specimens subjected to elevated moisture and more pronounced for sandwich specimens immersed in sea-water. After 30 days of exposure to high moisture, foam damage is visible in the form of cracks and pits on the cell walls. Optical examinations of expansional strains show that moisture absorbed by the foam penetrates only about to 2–3 mm from the core free surface for the 95% RH condition, while penetrates deeply for the immersed condition.     

Assessment of chemo-mechanical couplings in polymer matrix materials exposed to thermo-oxidative environments at high temperatures and under tensile loadings

The present paper is concerned with the experimental assessment of chemo-mechanical couplings in a polymer matrix material exposed to thermo-oxidative environments at high temperatures and under pure tensile loadings. A model developed within the thermodynamics of irreversible processes (TIP) states that oxygen reaction-diffusion in the polymer matrix should be affected by the strain tensor and its spatial gradient; the model motivates the design and the development of the experimental assessment, which is done by ultra micro-indentation (UMI) elastic modulus (EIT) measurements carried out - at room temperature - on unnotched and notched 977-2 polymer samples thermo-oxidized under tensile loadings.For the material and the loading conditions of the present research the EIT profiles are not influenced by the applied strain or by the strain gradients which develop close to the sample notches.     

Investigation into engineering properties and strength mechanism of grouted macadam composite materials

To further understand engineering properties of grouted macadam composite materials (GMCM) used as a surfacing layer in pavement, the mechanical properties and durability characteristics of GMCM were evaluated, and the relevant strength mechanisms were investigated at the micro level. Results indicate that GMCM has better high-temperature stability, fatigue performance and moisture stability than that of conventional asphalt mix, while it shows an acceptable decrease in low-temperature crack resistance due to the relative brittleness of hardened cement paste. The hardened cement paste also generates a spatial network crystalline lattice in asphalt mix skeleton to form a three-dimensional integral coagulation-crystalloid structure. This facilitates the asphalt mix skeleton and hardened cement paste to bear loads in unison and increase durability of the GMCM. Further, the fibre-like hydrated products of fresh cement slurry on the bitumen film surface increase the interfacial strength between bitumen and hardened cement paste due to toughening and bridging effects, which plays an important role to enhance mechanical properties and durability of GMCM. Finally, GMCM strength is from the internal friction of asphalt mix skeleton, the network structure of hardened cement paste and the adhesion between porous asphalt mix and hardened cement paste. It is concluded that GMCM can better meet the requirements of mechanical properties and durability characteristics than the conventional asphalt mix.     

进口氮压机排气温度高的故障分析

介绍进口氮压机三级排气温度高的现象,对其原因进行了分析,阐述处理措施和效果。