P91钢的焊接性及其焊接工艺

通过分析P91钢的焊接性,明确预防焊接冷裂纹是保证焊接质量的首要措施,焊前预热和焊后热处理直接决定焊接接头的硬度,硬度偏高则无法充分消除焊接接头内应力,硬度过低则会降低材料的高温持久强度.结合钢管规格与材质,拟定焊接工艺参数,进行焊接试验、热处理试验和力学性能检验,形成P91钢焊接工艺.采取焊前准备、控制坡口加工、实时...     

厚壁P92钢管道焊接热处理工艺试验研究

1 000 MW超超临界火力发电机组主蒸汽厚壁P92钢管道焊接热处理是火电建设工程中技术难度较高的一类问题，尤其是壁厚>100 mm的P92钢管道焊接热处理。文中结合某1 000 MW超超临界二次再热火电机组118 mm壁厚的主蒸汽P92钢管道的焊接热处理，焊接热处理过程中严格执行焊接工艺，并采用中频感应加热的方法对试样管进行了焊后热处理，热处理后焊接接头的硬度值、金相组织、力学性能数据完全满足P92钢的性能要求。该厚壁P92钢管道焊接热处理工艺方案可为后续同类型部件的焊接热处理提供借鉴。     

厚壁P92钢管道焊接接头中频感应热处理的应用实践

火力发电厂1000 MW机组主蒸汽厚壁P92钢管道焊接接头焊后热处理在火电建设工程中技术要求较高,尤其是壁厚大于100 mm的P92钢管道焊接接头。通过中频感应加热对1000 MW二次再热机组的壁厚为118 mm的主蒸汽P92钢管焊接接头进行了管道试样的焊后热处理。结果表明,热处理后焊缝及母材组织正常,焊缝硬度符合标准要求;同时依据试样管焊后热处理发现的问题提出了优化措施,在施工过程中降低升温速度和恒温温度、增加保温宽度,实现了121个同类型焊接接头焊后热处理一次合格。厚壁P92钢管道焊接接头中频感应热处理方案的成功应用,可为后续同类型部件的焊后热处理提供借鉴。     

A335 P91钢高压厚壁管SAW焊接技术

A335 P91钢抗高温氧化、抗蠕变性能和热强性良好,但合金含量高,属空冷马氏体钢,焊接时有较大的淬硬倾向,冷裂敏感性强。为保证A335 P91钢焊接接头在高温下安全运行的持久强度和足够的韧性,需对焊接和热处理工艺严格要求。采用集装箱式管道埋弧焊对A335 P91管道焊接进行了系列工艺开发试验,成功后应用于A335 P91管道的焊接施工,这是本公司首次将埋弧焊应用于A335 P91管道焊接。通过与传统手工焊比对分析,埋弧焊技术先进、经济效益显著,值得推广应用。     

F22/P91异种钢接头裂纹原因分析及焊接修复

某高压主汽门阀用F22/P91异种钢焊接接头运行时,表面及其内部产生裂纹。文中采用金相显微镜、SEM、显微硬度仪等对焊接裂纹进行检验。结果表明,P91钢及堆焊层强度低、焊接及热处理工艺不合理,是导致接头产生裂纹的主要原因。通过采用合理的焊接和热处理工艺,避免了异种钢接头裂纹的产生,确保了机组的安全可靠运行。     

P91导汽管焊后热处理对母材组织与性能影响

由于对P91焊缝的焊后回火热处理控制不当,导致过回火。过回火致使焊缝附近P91母材硬度降低到约145 HB,与正常管段硬度约205 HB相比降低了60 HB。采用光学显微镜对低硬度区和硬度合格区组织进行观察,结果显示低硬度区组织异常、组织劣化,硬度合格区组织正常。对低硬度区和硬度合格区常温、高温拉伸强度以及夏比冲击功进行了测试,并用扫描电镜对拉伸和冲击断口进行了分析。结果表明,低硬度区与硬度正常管段相比,拉伸强度、夏比冲击功降低,力学性能劣化,断口形貌不佳。分析认为过回火导致了P91组织异常,材料力学性能降低,影响了其长期安全使用,应予以更换或重新热处理。     

主蒸汽系统P91与P22小口径管道异种钢的焊接工艺

P91与P22钢焊接性均较差,两种钢材组成的异种钢焊接接头极易出现淬硬倾向并产生裂纹。此外,由于两种钢材在材料属性以及在焊接热处理要求方面的差异,加之产品管径较小容易影响加热器安装效果从而造成热处理质量下降,最终导致该异种钢焊接接头难以获得较为理想的综合力学性能,尤其是硬度指标更难以保证。为此,通过对核电主蒸汽系统P91与P22小口径管道的材料属性、焊接性能进行分析,按照焊前准备、焊接方法及焊接材料、焊接工艺参数、焊后热处理步骤实施工艺试验,结果表明,接头焊接质量检验、力学性能检验、微观金相检验、硬度检验均满足设计以及ASME规范相关要求。通过上述措施最终确定现场施焊的焊接工艺,将其应用于实际生产后效果良好,满足P91与P22小口径管道异种钢的焊接施工要求,为现场焊接提供了技术保证。     

某300 MW机组P91钢主汽大小头硬度异常原因分析及处理

对某300 MW机组进行金属监督检验时发现材质为P91钢的主汽大小头局部硬度值偏低、金相组织异常。经分析,其原因是主汽管道大小头在加工制造过程中进行热处理工艺和控制过程不当导致;提出了对存在问题的大小头进行更换的处理意见,并制订了焊接工艺要点。     

P91主蒸汽管道焊接接头的蠕变特性和寿命估算

对P91钢母材和焊接接头进行持久试验，研究P91钢的蠕变特性，采用等温线法和L-M参数法对持久强度进行外推，进而对P91钢制主蒸汽管道的蠕变寿命进行估算。     

T91钢焊缝硬度偏高分析及建议

对某电厂1000 MW机组锅炉过热器管屏T91钢对接焊缝进行了硬度测量、拉伸试验、弯曲试验、金相组织观察和焊接、热处理工艺分析。结果表明,硬度高于标准要求的焊缝金相组织为粗大的板条状马氏体,弯曲试验易发生断裂。分析认为,焊缝硬度高与焊接时线能量输入过大及热处理工艺执行不当有关,建议T91钢焊接应采用小的线能量输入,焊后最好进行整体热处理。     

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.     

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.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.